Do fructans cause laminitis?
Introduction
So what exactly are fructans?
How do fructans appear on a hay/grass analysis?
How are fructans digested?
Research using oligofructose/fructans to induce laminitis - Sepsis-Associated Laminitis (SAL)
Does fructan/OF overload cause endotoxaemia?
What is the lowest dose of OF that has caused laminitis?
Does fructan/OF overload affect insulin?
Is pasture associated laminitis SAL or endocrine?
Hyperinsulinaemia proven as a cause of laminitis - the endocrine cause
So pasture associated laminitis is almost certainly endocrine - but could it be due to fructans?
So where did the idea that fructans might contribute to endocrine laminitis come from?
So how does grass cause laminitis?
How much NSC/WSC/ESC/fructan is in grass?
What about fructans in hay?
How reliable is fructan analysis?
How much fructan could horses consume?
Conclusion
References and fructan research
Introduction
Laminitis has been caused by administering large amounts of oligofructose/inulin (a type of fructan) by nastogastric tube. However, does this have any relevance to pasture associated laminitis - can fructans in grass and hay cause or worsen laminitis, and if so, how?
Let's start with a reminder that there are now considered to be 3 distinct forms of laminitis (see conclusions: Katz and Bailey 2012):
1. Contralateral/supporting limb laminitis - not relevant to fructans/pasture associated laminitis
2. Inflammatory or SIRS laminitis - includes starch and oligofructose (fructan) overload
3. Endocrinopathic laminitis caused by hyperinsulinaemia (high levels of insulin) - EMS, PPID & corticosteroids
Laminitis has been caused by administering large amounts of oligofructose/inulin (a type of fructan) by nastogastric tube. However, does this have any relevance to pasture associated laminitis - can fructans in grass and hay cause or worsen laminitis, and if so, how?
Let's start with a reminder that there are now considered to be 3 distinct forms of laminitis (see conclusions: Katz and Bailey 2012):
1. Contralateral/supporting limb laminitis - not relevant to fructans/pasture associated laminitis
2. Inflammatory or SIRS laminitis - includes starch and oligofructose (fructan) overload
3. Endocrinopathic laminitis caused by hyperinsulinaemia (high levels of insulin) - EMS, PPID & corticosteroids
So what exactly are fructans?
During photosynthesis plants make sugar - sucrose, glucose and fructose. When sugar produced > sugar needed for plant growth (respiration), excess sugar is converted into storage carbohydrate. In cool season (C3) grass (as is found in the UK, northern Europe and northern USA), this storage carbohydrate is fructan. Sugar is produced in the leaves, but fructan is stored in the stem, where large amounts can potentially accumulate. Starch is mostly found only in seed heads in C3 grass. In warm season (C4) grass the storage carbohydrate is mainly starch (not fructan), which is stored in the leaves, with limited storage.
Fructans:
For more details about grass physiology see:
Grass physiology and its relation to nutritive value in feeding horses - Virkajarvi P, Saarijarvi K, Rinne M, Saastamoinen M
6th European Workshop Equine Nutrition 2011 p17
Inulin-type Fructans - Marcel Roberfroid 2006 p40 onwards.
How do fructans appear on a hay/grass analysis?
Many hay/grass analyses only list Water Soluble Carbohydrate (WSC), which may appear simply as "sugar", and starch.
WSC is the sum of Ethanol Soluble Carbohydrate (ESC) (sucrose, glucose & fructose) plus fructan.
So fructan = WSC minus ESC.
Non-Structural Carbohydrate (NSC) is the sum of WSC plus starch.
NB short-chain/low DP fructans may be included in ESC.
For more details see Testing for sugar/starch in feeds - Katy Watts, www.safergrass.org
How are fructans digested?
Shirazi-Beechey SP
Molecular insights into equine intestinal glucose transport
7th European Workshop on Equine Nutrition, Sept-Oct 2014, Germany
“The natural diet of the horse, pasture forage (grass), is fermented by the equine colonic microbiota to short chain fatty acids (SCFA), notably acetate, propionate and butyrate.”
A more useful definition of carbohydrates for horses would be hydrolysable carbohydrate, i.e. ESC plus starch, or NSC minus fructan, as sucrose, glucose, fructose and starch are digested by enzymes in the small intestine to glucose (and fructose) and influence blood glucose and insulin levels, but fructan cannot be hydrolysed by enzymes in the small intestine, and is fermented by micro-organisms, mostly in the large intestine, to volatile fatty acids and lactate, with the potential for large amounts to cause acidosis.
According to Coenen et al. 2006, inulin may be rapidly fermented before reaching the caecum/large intestine.
Ince et al. 2013 incubated grass fructan with digesta (contents) from the stomach and small intestine and found that polymeric (long-chain) fructan was partly degraded to oligo-fructan (shorter-chain). The research concluded that fructan in grass is not completely digested pre-caecally and reaches the hind gut, where it is fermented and lactate is produced. When grasses with high and moderate amounts of fructan were incubated with micro-organisms from the hind gut, there was greater fermentation and production of lactate from the grass higher in fructan.
Comment: the abstract states that laminitis may be elicted by fructans in pasture grasses - TLS has been unable to find any proof of this, so what do they base this statement on? Given that enzymes and other digestive juices will be produced in vivo in response to the chyme, how relevant is this research? Pre-caecally, was fructan degraded to fructose or glucose (or any mono or di-saccharides) that might have an effect on insulin levels? Was lactate the only product of fermentation of the ryegrasses, or were other VFAs produced?
Vosmer et al. 2012 looked at the effects of changing from a hay based diet to a grass (English ryegrass, tall fescue, horse grass mixture, cow grass mixture) or legume (lucerne, white clover) based diet in a model of a horse's hindgut. The grass mixtures contained the highest levels of fructan, with a maximum of 3.75 g/kg, but fructan did not cause a permanent pathological change in the hindgut-flora, even though gas formation and both anaerobic and aerobic bacterial numbers increased following the change to grass/legume.
Mackie and Wilkins 1988 examined the volatile fatty acid (VFA) content of the hind gut (cecum and ventral colon) in 11 adult horses that had been maintained on natural, unimproved mixed grass pasture (between July and August, and May and September, in Pretoria, South Africa), with hay in the 20 to 24 hours before examination. The pH in the cecum was 6.70 and in the colon 6.67. Acetate was the only VFA found in the small intestine. The mean VFA concentrations in the cecum and colon respectively in mM were:
Acetate 99.9, 98.5
Propionate 12.5, 11.0
Butyrate 3.8, 3.3
and the molar proportion of acetate:propionate:butyrate was 85:10:3, indicative of fibre fermentation. Acetate is indicative of a diet that is low in rapidly fermentable sugars or concentrates. Lactic acid is an end product of fermentation, but in the absence of readily fermentable soluble sugars in the diet, the lactic acid levels were negligible in the hind gut (0.1 mM), and lower than the small intestine (0.75 mM in the duodenum).
NB these horses spent their last 24 hours in an abattoir - it has to be considered that stress could have affected these results. The pasture and hay were not analysed.
Interestingly, short-chain fructans may have prebiotic effects.
See Digestive strategy and flexibility in horses with reference to dietary carbohydrates - RJ Geor
5th European Workshop Equine Nutrition 2010 p17
During photosynthesis plants make sugar - sucrose, glucose and fructose. When sugar produced > sugar needed for plant growth (respiration), excess sugar is converted into storage carbohydrate. In cool season (C3) grass (as is found in the UK, northern Europe and northern USA), this storage carbohydrate is fructan. Sugar is produced in the leaves, but fructan is stored in the stem, where large amounts can potentially accumulate. Starch is mostly found only in seed heads in C3 grass. In warm season (C4) grass the storage carbohydrate is mainly starch (not fructan), which is stored in the leaves, with limited storage.
Fructans:
- are water soluble polymers of fructose bonded to a terminal glucose.
- may be oligofructose e.g. inulin which is found in chicory, with β-2,1 linked polymers with degree of polymerisation (DP) <11; or levans, the predominant fructans found in grass, with β-2,6 linked polymers with degree of polymerisation (DP) 26 or higher.
- with lower DPs are likely to be more rapidly fermented than those with higher DPs - DP varies between species, e.g. from bromegrass which has 26 DP fructans up to 260 DP fructans in timothy.
- increase when grass can photosynthesize but can't grow, e.g. during cold weather, drought, and due to lack of nutrients.
- tend to be highest at the start and end of the growing season, particularly in regions with shorter growing seasons (e.g. further north).
- are reduced by topping/cutting grass as fructan stores are used to produce new leaves (therefore presumably grass that is grazed at a rate similar to regular topping will reduce fructan levels?).
For more details about grass physiology see:
Grass physiology and its relation to nutritive value in feeding horses - Virkajarvi P, Saarijarvi K, Rinne M, Saastamoinen M
6th European Workshop Equine Nutrition 2011 p17
Inulin-type Fructans - Marcel Roberfroid 2006 p40 onwards.
How do fructans appear on a hay/grass analysis?
Many hay/grass analyses only list Water Soluble Carbohydrate (WSC), which may appear simply as "sugar", and starch.
WSC is the sum of Ethanol Soluble Carbohydrate (ESC) (sucrose, glucose & fructose) plus fructan.
So fructan = WSC minus ESC.
Non-Structural Carbohydrate (NSC) is the sum of WSC plus starch.
NB short-chain/low DP fructans may be included in ESC.
For more details see Testing for sugar/starch in feeds - Katy Watts, www.safergrass.org
How are fructans digested?
Shirazi-Beechey SP
Molecular insights into equine intestinal glucose transport
7th European Workshop on Equine Nutrition, Sept-Oct 2014, Germany
“The natural diet of the horse, pasture forage (grass), is fermented by the equine colonic microbiota to short chain fatty acids (SCFA), notably acetate, propionate and butyrate.”
A more useful definition of carbohydrates for horses would be hydrolysable carbohydrate, i.e. ESC plus starch, or NSC minus fructan, as sucrose, glucose, fructose and starch are digested by enzymes in the small intestine to glucose (and fructose) and influence blood glucose and insulin levels, but fructan cannot be hydrolysed by enzymes in the small intestine, and is fermented by micro-organisms, mostly in the large intestine, to volatile fatty acids and lactate, with the potential for large amounts to cause acidosis.
According to Coenen et al. 2006, inulin may be rapidly fermented before reaching the caecum/large intestine.
Ince et al. 2013 incubated grass fructan with digesta (contents) from the stomach and small intestine and found that polymeric (long-chain) fructan was partly degraded to oligo-fructan (shorter-chain). The research concluded that fructan in grass is not completely digested pre-caecally and reaches the hind gut, where it is fermented and lactate is produced. When grasses with high and moderate amounts of fructan were incubated with micro-organisms from the hind gut, there was greater fermentation and production of lactate from the grass higher in fructan.
Comment: the abstract states that laminitis may be elicted by fructans in pasture grasses - TLS has been unable to find any proof of this, so what do they base this statement on? Given that enzymes and other digestive juices will be produced in vivo in response to the chyme, how relevant is this research? Pre-caecally, was fructan degraded to fructose or glucose (or any mono or di-saccharides) that might have an effect on insulin levels? Was lactate the only product of fermentation of the ryegrasses, or were other VFAs produced?
Vosmer et al. 2012 looked at the effects of changing from a hay based diet to a grass (English ryegrass, tall fescue, horse grass mixture, cow grass mixture) or legume (lucerne, white clover) based diet in a model of a horse's hindgut. The grass mixtures contained the highest levels of fructan, with a maximum of 3.75 g/kg, but fructan did not cause a permanent pathological change in the hindgut-flora, even though gas formation and both anaerobic and aerobic bacterial numbers increased following the change to grass/legume.
Mackie and Wilkins 1988 examined the volatile fatty acid (VFA) content of the hind gut (cecum and ventral colon) in 11 adult horses that had been maintained on natural, unimproved mixed grass pasture (between July and August, and May and September, in Pretoria, South Africa), with hay in the 20 to 24 hours before examination. The pH in the cecum was 6.70 and in the colon 6.67. Acetate was the only VFA found in the small intestine. The mean VFA concentrations in the cecum and colon respectively in mM were:
Acetate 99.9, 98.5
Propionate 12.5, 11.0
Butyrate 3.8, 3.3
and the molar proportion of acetate:propionate:butyrate was 85:10:3, indicative of fibre fermentation. Acetate is indicative of a diet that is low in rapidly fermentable sugars or concentrates. Lactic acid is an end product of fermentation, but in the absence of readily fermentable soluble sugars in the diet, the lactic acid levels were negligible in the hind gut (0.1 mM), and lower than the small intestine (0.75 mM in the duodenum).
NB these horses spent their last 24 hours in an abattoir - it has to be considered that stress could have affected these results. The pasture and hay were not analysed.
Interestingly, short-chain fructans may have prebiotic effects.
See Digestive strategy and flexibility in horses with reference to dietary carbohydrates - RJ Geor
5th European Workshop Equine Nutrition 2010 p17
Research using oligofructose/fructans to induce laminitis - Sepsis-Associated Laminitis
NB Research uses oligofructose, a short-chain low DP fructan (usually Raftilose - an "inulin-like" fructan).
The first research using oligofructose was Equine Laminitis
C. C. Pollitt, M. Kyaw-Tanner, K. R. French, A. W. Van Eps, J. K. Hendrikz and M. Daradka
AAEP 2003
Horses given 7.5 g/kg BW OF (Raftilose) by nasogastric tube developed clinical and histological laminitis in at least one foot within 48 hours. None developed colic. Higher doses (10 g/kg BW and 12.5 g/kg BW) were associated with more severe histological laminitis. All but one horse was given flunixin meglumine at 32 h to alleviate clinical signs of endotoxaemia. All horses developed profuse diarrhoea at around 18 h that ceased by 36 - 44 h. Pyrexia and elevated heart rate peaked between 16 and 20 h and returned to near normal by 48 h. Faecal pH began to fall within 4 h of dosing, reaching its lowest value (3.7) at around 18 h. There was significant loss of bicarbonate after 12 h, which remained low for 12 h then recovered. Blood D-lactate of bacterial origin peaked at 24 h at 2.87 mmol/l. Plasma glucose peaked at 24 - 28 h. Cortisol was not greater than controls. Plasma insulin was not significant, although horses treated with 12.5 g/kg BW had the highest values.
This research established that a storage carbohydrate other than starch can induce laminitis.
OF cannot be hydrolysed in the small intestine, therefore it passes into the caecum, where it undergoes rapid microbial fermentation. Gram positive bacteria, notably Streptococcus bovis and S. equinus, proliferate preferentially and temporarily become the dominant microflora. During OF fermentation Gram positive microflora produce lactic acid, causing the low hindgut pH and peak of blood lactic acid at 24 h (hindgut bacteria produce D-lactate and L-lactate, mammals produce only L-lactate, therefore the presence of D-lactate indicates it has come from fermentation). D-lactate disappeared from the blood by 40 h, suggesting there is a sharp decline in D-lactate producing organisms after an early rapid population explosion. The large but temporary gram positive bacteria could liberate exotoxins and endotoxins when they die off at the end of their growth phase or when the OF is exhausted, which could penetrate the leaky mucosal barrier of the large intestine.
The research concluded that laminitis seems to be the result of fermentation of pasture OF by gram positive hindgut microbes.
However, in 2003 insulin had not been proven as a cause of laminitis. Simple sugar levels were not considered in this research.
Symptoms of fructan overload in later research:
Milinovich et al 2006 gave oligofructose and found a sharp decline in faecal pH (marked hindgut acidosis) and alterations in microbial populations in caecum and large intestine.
Van Eps and Pollitt 2006:
In the developmental stages of oligofructose-induced laminitis (using bolus doses of 7.5 to 12.5 g/kg by stomach tube), significant quantities of d-lactate (2 to 3 mmol/L) have been observed in the plasma between 4 and 32 h after induction.
Van Eps and Pollitt 2009 gave 10 g/kg BW oligofructose by nasogastric tube – all horses developed diarrhoea, pyrexia and tachycardia from 20 hrs.
Keller et al. 2011:
7.5 g/kg BW oligofructose (a partial hydrolysate of inulin) was administerd via nasogastric tube.
All horses had diarrhoea 6 - 24 hours after OF administration, increased digital pulse intensity and weight shifting of front feet 15 - 24 hours after induction.
All horses had increases in plasma lactate 15 - 24 hours after administration, peaking around 18 - 21 hours. The mean s.d. increase in lactate concentrations at 21 hours after administration was 286%
Milinovich et al. 2008:
10 g/kg bw oligofructose (Raftilose) administered by nasogastric tube:
By 8 hours all horses had depressed appetite,
By 16 hours all had profuse watery diarrhoea,
By 6 - 12 hours all horses developed caecal acidosis with pH < 5, caecal pH was lower than baseline by 2 hours.
Laminitis was seen in 3 horses between 20 and 28 hours, and as late as 43 hours in the last horse.
Histological changes in the feet due to laminitis were first seen at 12 hours in 2 horses, 18 hours in 1 horse and 30 hours in 2 horses.
Caecal fluid lactate increased almost immediately.
Katz and Bailey 2012 - laminitis tends to develop 24 - 36 hrs following OF administration, earliest histological changes are loss of normal shape and arrangement of the lamellar basal and parabasal cells, with lysis and separation of the lamellar basement membrane.
Does fructan/OF overload cause endotoxaemia?
Toth et al. 2010 found that endotoxaemia exacerbated insulin resistance.
Insulin resistance appears to be provoked by systemic inflammation, as well as contributing to it (Katz & Bailey 2012).
What is the lowest dose of OF that has caused laminitis?
Kalck et al. 2009 administered 5 g/kg BW OF by nasogastric tube after a 6 day introductory period of feeding 1 g/kg OF with oats. 3 out of 8 horses developed developed Obel grade 1 or 2 laminitis. Glucose dynamics were altered but insulin dynamics were unaltered. Other horses were given 7.5 g/kg BW OF in the same manner, 4/4 developed laminitis.
Toth et al 2009 also administered 5 g/kg BW OF by nasogastric tube. 2/8 horses developed Obel grade 1 or 2 laminitis. OF induced signs consistent with systemic inflammation. Insulin sensitivity decreased, but acute insulin response to glucose did not increase significantly.
Does fructan/OF overload affect insulin?
Katz & Bailey 2012 - no OF models have found evidence of hyperinsulinaemia. See
Van Eps & Pollitt 2006
Kalck et al. 2009
Although a mild degree of IR has been observed -
Toth et al. 2009 and Toth et al. 2010 found that endotoxaemia and carbohydrate overload (OF) reduce insulin sensitivity in horses.
Endotoxaemia affects insulin and glucose:
Toth et al 2008 healthy horses injected with LPS endotoxin had reduced insulin sensitivity for 24 hrs after treatment (13/16 horses showed mild colic and leukopenia).
If fructan was causing pasture associated laminitis by SIRS, wouldn't all horses would be equally susceptible to hind gut disturbance, not just insulin resistant horses?
In every case of OF-induced laminitis, symptoms of systemic illness were seen - increased temperature, diarrhoea, changes to white blood cells and other blood results. These are generally not see with pasture-associated laminitis.
NB Research uses oligofructose, a short-chain low DP fructan (usually Raftilose - an "inulin-like" fructan).
The first research using oligofructose was Equine Laminitis
C. C. Pollitt, M. Kyaw-Tanner, K. R. French, A. W. Van Eps, J. K. Hendrikz and M. Daradka
AAEP 2003
Horses given 7.5 g/kg BW OF (Raftilose) by nasogastric tube developed clinical and histological laminitis in at least one foot within 48 hours. None developed colic. Higher doses (10 g/kg BW and 12.5 g/kg BW) were associated with more severe histological laminitis. All but one horse was given flunixin meglumine at 32 h to alleviate clinical signs of endotoxaemia. All horses developed profuse diarrhoea at around 18 h that ceased by 36 - 44 h. Pyrexia and elevated heart rate peaked between 16 and 20 h and returned to near normal by 48 h. Faecal pH began to fall within 4 h of dosing, reaching its lowest value (3.7) at around 18 h. There was significant loss of bicarbonate after 12 h, which remained low for 12 h then recovered. Blood D-lactate of bacterial origin peaked at 24 h at 2.87 mmol/l. Plasma glucose peaked at 24 - 28 h. Cortisol was not greater than controls. Plasma insulin was not significant, although horses treated with 12.5 g/kg BW had the highest values.
This research established that a storage carbohydrate other than starch can induce laminitis.
OF cannot be hydrolysed in the small intestine, therefore it passes into the caecum, where it undergoes rapid microbial fermentation. Gram positive bacteria, notably Streptococcus bovis and S. equinus, proliferate preferentially and temporarily become the dominant microflora. During OF fermentation Gram positive microflora produce lactic acid, causing the low hindgut pH and peak of blood lactic acid at 24 h (hindgut bacteria produce D-lactate and L-lactate, mammals produce only L-lactate, therefore the presence of D-lactate indicates it has come from fermentation). D-lactate disappeared from the blood by 40 h, suggesting there is a sharp decline in D-lactate producing organisms after an early rapid population explosion. The large but temporary gram positive bacteria could liberate exotoxins and endotoxins when they die off at the end of their growth phase or when the OF is exhausted, which could penetrate the leaky mucosal barrier of the large intestine.
The research concluded that laminitis seems to be the result of fermentation of pasture OF by gram positive hindgut microbes.
However, in 2003 insulin had not been proven as a cause of laminitis. Simple sugar levels were not considered in this research.
Symptoms of fructan overload in later research:
Milinovich et al 2006 gave oligofructose and found a sharp decline in faecal pH (marked hindgut acidosis) and alterations in microbial populations in caecum and large intestine.
Van Eps and Pollitt 2006:
In the developmental stages of oligofructose-induced laminitis (using bolus doses of 7.5 to 12.5 g/kg by stomach tube), significant quantities of d-lactate (2 to 3 mmol/L) have been observed in the plasma between 4 and 32 h after induction.
Van Eps and Pollitt 2009 gave 10 g/kg BW oligofructose by nasogastric tube – all horses developed diarrhoea, pyrexia and tachycardia from 20 hrs.
Keller et al. 2011:
7.5 g/kg BW oligofructose (a partial hydrolysate of inulin) was administerd via nasogastric tube.
All horses had diarrhoea 6 - 24 hours after OF administration, increased digital pulse intensity and weight shifting of front feet 15 - 24 hours after induction.
All horses had increases in plasma lactate 15 - 24 hours after administration, peaking around 18 - 21 hours. The mean s.d. increase in lactate concentrations at 21 hours after administration was 286%
Milinovich et al. 2008:
10 g/kg bw oligofructose (Raftilose) administered by nasogastric tube:
By 8 hours all horses had depressed appetite,
By 16 hours all had profuse watery diarrhoea,
By 6 - 12 hours all horses developed caecal acidosis with pH < 5, caecal pH was lower than baseline by 2 hours.
Laminitis was seen in 3 horses between 20 and 28 hours, and as late as 43 hours in the last horse.
Histological changes in the feet due to laminitis were first seen at 12 hours in 2 horses, 18 hours in 1 horse and 30 hours in 2 horses.
Caecal fluid lactate increased almost immediately.
Katz and Bailey 2012 - laminitis tends to develop 24 - 36 hrs following OF administration, earliest histological changes are loss of normal shape and arrangement of the lamellar basal and parabasal cells, with lysis and separation of the lamellar basement membrane.
Does fructan/OF overload cause endotoxaemia?
Toth et al. 2010 found that endotoxaemia exacerbated insulin resistance.
Insulin resistance appears to be provoked by systemic inflammation, as well as contributing to it (Katz & Bailey 2012).
What is the lowest dose of OF that has caused laminitis?
Kalck et al. 2009 administered 5 g/kg BW OF by nasogastric tube after a 6 day introductory period of feeding 1 g/kg OF with oats. 3 out of 8 horses developed developed Obel grade 1 or 2 laminitis. Glucose dynamics were altered but insulin dynamics were unaltered. Other horses were given 7.5 g/kg BW OF in the same manner, 4/4 developed laminitis.
Toth et al 2009 also administered 5 g/kg BW OF by nasogastric tube. 2/8 horses developed Obel grade 1 or 2 laminitis. OF induced signs consistent with systemic inflammation. Insulin sensitivity decreased, but acute insulin response to glucose did not increase significantly.
Does fructan/OF overload affect insulin?
Katz & Bailey 2012 - no OF models have found evidence of hyperinsulinaemia. See
Van Eps & Pollitt 2006
Kalck et al. 2009
Although a mild degree of IR has been observed -
Toth et al. 2009 and Toth et al. 2010 found that endotoxaemia and carbohydrate overload (OF) reduce insulin sensitivity in horses.
Endotoxaemia affects insulin and glucose:
Toth et al 2008 healthy horses injected with LPS endotoxin had reduced insulin sensitivity for 24 hrs after treatment (13/16 horses showed mild colic and leukopenia).
If fructan was causing pasture associated laminitis by SIRS, wouldn't all horses would be equally susceptible to hind gut disturbance, not just insulin resistant horses?
In every case of OF-induced laminitis, symptoms of systemic illness were seen - increased temperature, diarrhoea, changes to white blood cells and other blood results. These are generally not see with pasture-associated laminitis.
Is pasture associated laminitis SAL or endocrine?
Some horses seem predisposed to laminitis while others grazing the same pasture are never affected - why?
In her August 2011 webinar sponsored by Boehringer Ingelheim, Cathy McGowan said that much has changed in our understanding of laminitis in the last 5 years:
1. We now know there are 3 main categories of laminitis:
- SIRS (now called Sepsis-Associated Laminitis) - systemic inflammatory/intestinal events where the horse is systemically ill,
- weight-bearing,
- endocrine - hormones cause laminitis, but these horses are not systemically ill.
2. We used to think pasture associated laminitis was due to carbohydrate overload, we now know that fructans in grass do not cause laminitis. Horses with PAL have no signs of inflammatory/systemic disease, no raised temperature, no changes in their white blood cell counts, no diarrhoea. Pasture associated laminitis is an endocrine disorder with an abnormal insulin response.
3. Endocrinopathic laminitis is the most common cause of laminitis - Karikoski et al 2011.
4. The insulin models of laminitis (Asplin et al. 2007, de Laat et al. 2011) have shown that the histopathology (changes to cells) in the feet are different between SIRS and endocrine laminitis, shown that low levels of insulin can cause laminitic histopathology, and moved the focus of the cause of pasture associated laminitis away from inflammatory substances in grass (fructans, vasoactive amines) to metabolic/hormonal disturbances (see below).
Andy Durham said much the same in his February 2012 webinar sponsored by Boehringer Ingelheim - around 90% of laminitis cases have an endocrinopathic cause (Karikoski et al 2011) - in fact it's probably more than 90% - young, fit, non-obese horses get laminitis less than 10% of the time.
Fructans of 5 g/kg BW or more administered by stomach tube in one hit have been used experimentally to cause acidosis in the large intestine, leading to the mucosal barrier being compromised, releasing toxins which are thought to trigger laminitis. At realistic levels of grass intake, fructans do not cause colitis and large intestine mucosal barrier compromise, but low levels of fructans/sugars do cause hyperinsulinaemia in laminitis-prone ponies with EMS and PPID. Grass-induced laminitis is endocrine laminitis.
Some horses seem predisposed to laminitis while others grazing the same pasture are never affected - why?
In her August 2011 webinar sponsored by Boehringer Ingelheim, Cathy McGowan said that much has changed in our understanding of laminitis in the last 5 years:
1. We now know there are 3 main categories of laminitis:
- SIRS (now called Sepsis-Associated Laminitis) - systemic inflammatory/intestinal events where the horse is systemically ill,
- weight-bearing,
- endocrine - hormones cause laminitis, but these horses are not systemically ill.
2. We used to think pasture associated laminitis was due to carbohydrate overload, we now know that fructans in grass do not cause laminitis. Horses with PAL have no signs of inflammatory/systemic disease, no raised temperature, no changes in their white blood cell counts, no diarrhoea. Pasture associated laminitis is an endocrine disorder with an abnormal insulin response.
3. Endocrinopathic laminitis is the most common cause of laminitis - Karikoski et al 2011.
4. The insulin models of laminitis (Asplin et al. 2007, de Laat et al. 2011) have shown that the histopathology (changes to cells) in the feet are different between SIRS and endocrine laminitis, shown that low levels of insulin can cause laminitic histopathology, and moved the focus of the cause of pasture associated laminitis away from inflammatory substances in grass (fructans, vasoactive amines) to metabolic/hormonal disturbances (see below).
Andy Durham said much the same in his February 2012 webinar sponsored by Boehringer Ingelheim - around 90% of laminitis cases have an endocrinopathic cause (Karikoski et al 2011) - in fact it's probably more than 90% - young, fit, non-obese horses get laminitis less than 10% of the time.
Fructans of 5 g/kg BW or more administered by stomach tube in one hit have been used experimentally to cause acidosis in the large intestine, leading to the mucosal barrier being compromised, releasing toxins which are thought to trigger laminitis. At realistic levels of grass intake, fructans do not cause colitis and large intestine mucosal barrier compromise, but low levels of fructans/sugars do cause hyperinsulinaemia in laminitis-prone ponies with EMS and PPID. Grass-induced laminitis is endocrine laminitis.
Hyperinsulinaemia proven as a cause of laminitis - the endocrine cause
It was only in 2007 that Katie Asplin's research proved that hyperinsulinaemia or insulin toxicity causes pasture-associated/endocrinopathic laminitis in healthy, non-insulin resistant ponies with no changes to blood glucose:
Asplin KE, Sillence MN, Pollitt CC, McGowan CM
Induction of laminitis by prolonged hyperinsulinaemia in clinically normal ponies
The Veterinary Journal Vol 174, Issue 3, November 2007, Pages 530-535
Insulin was infused for 72 hours or until clinical signs of laminitis were seen - increased digital pulses, increased hoof heat over the dorsal hoof wall, weight shifting, lameness (Obel grade 2). All treated ponies developed laminitis in all 4 hooves. Obel grade 1 was evident by 33 h, Obel grade 2 by 56 h. Respiration rate increased from 19 to 36, heart rate increased from 49 to 70 bpm. Rectal temperature remained normal. Basal insulin was 15.7 uIU/ml, glucose 5.2 mmol/l, insulin averaged 1036 uIU/ml.
Laminar histology showed elongated and tapered tips to secondary epidermal laminae, disintegrated basement membrane and rounded basal cell nuclei.
The research concluded that high carbohydrate intakes, e.g. high NSC diets or lush pasture, could drive insulin levels beyond a tolerance threshold in insulin-resistant horses, causing laminitis. It was mentioned that high NSC diets impair glucose tolerance, and high NSC diets should be substituted with low glycaemic index feeds - it's all about glucose causing high insulin. Glucose being digested in the small intestine, from simple sugars and starch - nothing to do with fructans. "There was no clinical evidence of gastrointestinal involvement and the ponies showed no signs of systemic illness throughout the experiment".
Need to remember that unlike humans, horses rarely develop pancreatic exhaustion and are capable of producing exceptionally high serum insulin concentrations.
Walsh et al 2009 found that plasma insulin correlated with laminitis grade and that the onset of laminitis was associated with hyperinsulinaemia > 100 uIU/ml.
Melody de Laat's research Insulin-Induced Laminitis published by the RIRDC in 2011 states "laminitis occuring in insulin-resistant horses and ponies is often accompanied by the intake of large amounts of non-structural carbohydrate rich pasture." "This increased dietary intake of glucose may play a role in disease development in cases of pasture-associated laminitis." "Further, the insulin model of laminitis necessitates the administration of large amounts of glucose." "Horses rarely become hyperglycaemic, so either the relentless insulin production by the pancreas in response to the glucose contributes to lamellar failure, or the glucose itself may be toxic to the tissues." Insulin sensitive horses subjected to a hyperglycaemic clamp for 48 hrs became hyperinsulinaemic within 4 hrs - mean glucose 10.7 mmol/l and mean insulin 208 uIU/ml. Clinicial signs of laminitis or lameness were not seen, appetite, heart rate and respiratory rate remained normal, haematology and biochemistry blood results were normal other than hyperinsulinaemia and hyperglycaemia. Lamellar pathology (lengthening and narrowing of secondary epidermal laminae, increased mitotic figures, apoptotic bodies, leucocytes in the dermis, but no basement membrane disadhesion) was found in all horses after 48 hrs, in 1 foot in 1 horse, both front feet in 2 horses and all 4 feet in 1 horse. This research confirmed that insulin causes sub-clinical lamellar pathology at levels at or below 200 uIU/ml, and concluded that glucose does not appear to induce laminitis in the abscence of hyperinsulinaemia.
Healthy horses were subjected to a prolonged-euglycaemic, hyperinsulinaemic clamp with mean insulin ranging 811 - 1036 uIU/ml. All of the treated horses developed laminitis within 48 hrs, increased digital pulses and episodic shifting of feet was seen by 32 hrs, constant shifting of feet (Obel grade 1) was seen by 41 hrs. All treated horses had no change in blood haematology and biochemistry, heart rate, respiratory rate or temperature. Laminitis was confirmed histologically in 4 feet (3 horses) and 3 feet (1 horse - the lightest in weight). Lamellar changes included mitosis, apoptosis, lamellar lengthening and narrowing, and basement membrane disruption/dysadhesion and were seen as early as 6 hrs from onset of hyperinsulinaemia. The hoof surface wall temperature of treated horses was constantly elevated above control horses, suggesting vasodilation.
"Alimentary forms of laminitis are usually associated with overt clinical signs such as depression, diarrhoea or fever, whereas hyperinsulinaemic laminitis is not."
Histological comparisons were made between the hyperinsulinaemic horses and horses treated with 10 g/kg oligofructose who developed laminitis and were euthanized 48 hrs after OF administration. OF horses had a greater degree of basement membrane separation and significantly greater numbers of leucocytes infiltrating the dermal connective tissue. Hyperinsulinaemic horses had minimal MMP activity (unlike OF horses), suggesting that basement membrane proteolysis by MMPs is unlikely to occur in endocrinopathic laminitis
So this suggests that endocrine laminitis is quite different to laminitis induced by oligo-fructose/fructan. Horses with OF laminitis will be obviously ill, horses with endocrine laminitis will have laminitis as their primary illness. High levels of glucose from high NRC feed is the likely cause of hyperinsulinaemia.
Trieber et al. 2006 - elevated serum insulin distinguished ponies susceptible to laminitis from those that weren't.
Effects of PPID, season and pasture diet on blood, ACTH and metabolite concentrations in horses - Sarah Elliott MSc thesis
Positive correlation between mean ESC and mean insulin concentration in grazing horses (see p 37). Higher glucose and insulin concentrations appeared to correspond with increases in simple sugar intake on pasture.
It was only in 2007 that Katie Asplin's research proved that hyperinsulinaemia or insulin toxicity causes pasture-associated/endocrinopathic laminitis in healthy, non-insulin resistant ponies with no changes to blood glucose:
Asplin KE, Sillence MN, Pollitt CC, McGowan CM
Induction of laminitis by prolonged hyperinsulinaemia in clinically normal ponies
The Veterinary Journal Vol 174, Issue 3, November 2007, Pages 530-535
Insulin was infused for 72 hours or until clinical signs of laminitis were seen - increased digital pulses, increased hoof heat over the dorsal hoof wall, weight shifting, lameness (Obel grade 2). All treated ponies developed laminitis in all 4 hooves. Obel grade 1 was evident by 33 h, Obel grade 2 by 56 h. Respiration rate increased from 19 to 36, heart rate increased from 49 to 70 bpm. Rectal temperature remained normal. Basal insulin was 15.7 uIU/ml, glucose 5.2 mmol/l, insulin averaged 1036 uIU/ml.
Laminar histology showed elongated and tapered tips to secondary epidermal laminae, disintegrated basement membrane and rounded basal cell nuclei.
The research concluded that high carbohydrate intakes, e.g. high NSC diets or lush pasture, could drive insulin levels beyond a tolerance threshold in insulin-resistant horses, causing laminitis. It was mentioned that high NSC diets impair glucose tolerance, and high NSC diets should be substituted with low glycaemic index feeds - it's all about glucose causing high insulin. Glucose being digested in the small intestine, from simple sugars and starch - nothing to do with fructans. "There was no clinical evidence of gastrointestinal involvement and the ponies showed no signs of systemic illness throughout the experiment".
Need to remember that unlike humans, horses rarely develop pancreatic exhaustion and are capable of producing exceptionally high serum insulin concentrations.
Walsh et al 2009 found that plasma insulin correlated with laminitis grade and that the onset of laminitis was associated with hyperinsulinaemia > 100 uIU/ml.
Melody de Laat's research Insulin-Induced Laminitis published by the RIRDC in 2011 states "laminitis occuring in insulin-resistant horses and ponies is often accompanied by the intake of large amounts of non-structural carbohydrate rich pasture." "This increased dietary intake of glucose may play a role in disease development in cases of pasture-associated laminitis." "Further, the insulin model of laminitis necessitates the administration of large amounts of glucose." "Horses rarely become hyperglycaemic, so either the relentless insulin production by the pancreas in response to the glucose contributes to lamellar failure, or the glucose itself may be toxic to the tissues." Insulin sensitive horses subjected to a hyperglycaemic clamp for 48 hrs became hyperinsulinaemic within 4 hrs - mean glucose 10.7 mmol/l and mean insulin 208 uIU/ml. Clinicial signs of laminitis or lameness were not seen, appetite, heart rate and respiratory rate remained normal, haematology and biochemistry blood results were normal other than hyperinsulinaemia and hyperglycaemia. Lamellar pathology (lengthening and narrowing of secondary epidermal laminae, increased mitotic figures, apoptotic bodies, leucocytes in the dermis, but no basement membrane disadhesion) was found in all horses after 48 hrs, in 1 foot in 1 horse, both front feet in 2 horses and all 4 feet in 1 horse. This research confirmed that insulin causes sub-clinical lamellar pathology at levels at or below 200 uIU/ml, and concluded that glucose does not appear to induce laminitis in the abscence of hyperinsulinaemia.
Healthy horses were subjected to a prolonged-euglycaemic, hyperinsulinaemic clamp with mean insulin ranging 811 - 1036 uIU/ml. All of the treated horses developed laminitis within 48 hrs, increased digital pulses and episodic shifting of feet was seen by 32 hrs, constant shifting of feet (Obel grade 1) was seen by 41 hrs. All treated horses had no change in blood haematology and biochemistry, heart rate, respiratory rate or temperature. Laminitis was confirmed histologically in 4 feet (3 horses) and 3 feet (1 horse - the lightest in weight). Lamellar changes included mitosis, apoptosis, lamellar lengthening and narrowing, and basement membrane disruption/dysadhesion and were seen as early as 6 hrs from onset of hyperinsulinaemia. The hoof surface wall temperature of treated horses was constantly elevated above control horses, suggesting vasodilation.
"Alimentary forms of laminitis are usually associated with overt clinical signs such as depression, diarrhoea or fever, whereas hyperinsulinaemic laminitis is not."
Histological comparisons were made between the hyperinsulinaemic horses and horses treated with 10 g/kg oligofructose who developed laminitis and were euthanized 48 hrs after OF administration. OF horses had a greater degree of basement membrane separation and significantly greater numbers of leucocytes infiltrating the dermal connective tissue. Hyperinsulinaemic horses had minimal MMP activity (unlike OF horses), suggesting that basement membrane proteolysis by MMPs is unlikely to occur in endocrinopathic laminitis
So this suggests that endocrine laminitis is quite different to laminitis induced by oligo-fructose/fructan. Horses with OF laminitis will be obviously ill, horses with endocrine laminitis will have laminitis as their primary illness. High levels of glucose from high NRC feed is the likely cause of hyperinsulinaemia.
Trieber et al. 2006 - elevated serum insulin distinguished ponies susceptible to laminitis from those that weren't.
Effects of PPID, season and pasture diet on blood, ACTH and metabolite concentrations in horses - Sarah Elliott MSc thesis
Positive correlation between mean ESC and mean insulin concentration in grazing horses (see p 37). Higher glucose and insulin concentrations appeared to correspond with increases in simple sugar intake on pasture.
So pasture associated laminitis is almost certainly endocrine - but could it be due to fructans?
In their review of recent advances and current hypotheses on the pathogenesis of acute laminitis (2012), Katz and Bailey say: "excessive ingestion of carbohydrate (i.e. starch or possibly fructan from pasture) is one of the more common causes of laminitis,". (Given that Karikoski found that 89% of horses presented for laminitis at a first opinion/referral equine hospital had endocrinopathic laminitis, "common" relating to carbohydrate overload might be disputed!). Note that they say "possibly fructan from pasture" - there is no proof that fructans in pasture cause laminitis. OF overload in the hindgut causes a severe and rapid change in the hindgut bacterial populations, particularly a rapid proliferation of Gram positive bacteria, which produces a profound drop in pH as well as profuse diarrhoea. Endotoxin has been found in horses with OF induced laminitis.
A significant proportion of laminitis cases occur at pasture. Pasture can contain large amounts of fructans - Longland & Byrd 2006 - which may be enough to cause changes in the hindgut microflora - Crawford 2007.
But recent debate questions whether the OF overload model reflects fructans in pasture (inulin is not the main form of fructan found in pasture).
Kalck 2009 induced laminitis in 3/8 horses with 5 g/kg BW by nasogastric tube.
OF overload causes laminitis in any type of horse. Pasture associated laminitis generally occurs in horses with insulin resistance, and pasture associated laminitis is considered by many to be a form of EMS - horses that get laminitis from eating grass are generally either overweight or have regional adiposity and test positive for EMS or PPID (particularly when dynamic tests are used).
Increases in grass NSC levels tend to coincide with increased incidence of pasture associated laminitis - Longland & Byrd 2006, Watts 2004.
Grazing on pasture increases plasma insulin concentrations depending on the metabolic status of the horse - Geor 2009.
Katz & Bailey suggest that feeding inulin also increases plasma insulin concentrations in IR individuals - Bailey 2007 and Borer 2012 - but we show (below) that this cannot be concluded from either of these papers and that ESC (particularly glucose) was the more likely cause of increases in insulin concentrations in IR ponies.
de Laat's 2011 research showed that laminitic changes in the feet happen at insulin concentrations of 200 uIU/ml or lower. Walsh et al 2009 found that the onset of laminitis was associated with hyperinsulinaemia > 100 uIU/ml.
Insulin does not appear to play a role in the OF overload model (Milinovich 2006), but horses with pasture associated laminitis generally have insulin concentrations above normal, or an above normal response to a dynamic test such as the oral glucose test.
Katz and Bailey conclude "In pasture-associated laminitis, although this condition may have multiple contributors, it is highly likely that hyperinsulinaemia and/or IR play a significant role; the effects of pasture fructans being fermented in the large intestine may not be sufficient to cause laminitis without other metabolic triggers such as the additional effects of insulin." It may be that rapid fermentation of fructans contribute to the development of laminitis - but research adding 3 g/kg BW inulin making a total of 6.1 g/kg BW fructan (Bailey et al. 2007, Crawford et al. 2007) found no signs of lameness or laminitis. Bailey made no reference to any clinical symptoms being observed. Crawford made no reference to any clinical symptoms being observed, other than transient increases in digital pulse pressure in 1 or 2 limbs, a slight decrease in dung pH and increase in dung amines which could have been attributable to the sudden change of diet from hay to Readigrass.
Fructose feeding in other species contributes to IR, but there is no evidence (at the moment) that fructans are digested to fructose in the horse.
More research feeding fructans to horses:
Glatter M, Bochnia M, Goetz F, Gottschalk J, Koeller G, Mielenz N, Hillegeist D, Greef JM, Einspanier A, Zeyner A
Glycaemic and insulinaemic responses of adult healthy warm-blooded mares following feeding with Jerusalem artichoke meal
J Anim Physiol Anim Nutr (Berl). 2017 Jun;101 Suppl 1:69-78. doi: 10.1111/jpn.12669
In their review of recent advances and current hypotheses on the pathogenesis of acute laminitis (2012), Katz and Bailey say: "excessive ingestion of carbohydrate (i.e. starch or possibly fructan from pasture) is one of the more common causes of laminitis,". (Given that Karikoski found that 89% of horses presented for laminitis at a first opinion/referral equine hospital had endocrinopathic laminitis, "common" relating to carbohydrate overload might be disputed!). Note that they say "possibly fructan from pasture" - there is no proof that fructans in pasture cause laminitis. OF overload in the hindgut causes a severe and rapid change in the hindgut bacterial populations, particularly a rapid proliferation of Gram positive bacteria, which produces a profound drop in pH as well as profuse diarrhoea. Endotoxin has been found in horses with OF induced laminitis.
A significant proportion of laminitis cases occur at pasture. Pasture can contain large amounts of fructans - Longland & Byrd 2006 - which may be enough to cause changes in the hindgut microflora - Crawford 2007.
But recent debate questions whether the OF overload model reflects fructans in pasture (inulin is not the main form of fructan found in pasture).
Kalck 2009 induced laminitis in 3/8 horses with 5 g/kg BW by nasogastric tube.
OF overload causes laminitis in any type of horse. Pasture associated laminitis generally occurs in horses with insulin resistance, and pasture associated laminitis is considered by many to be a form of EMS - horses that get laminitis from eating grass are generally either overweight or have regional adiposity and test positive for EMS or PPID (particularly when dynamic tests are used).
Increases in grass NSC levels tend to coincide with increased incidence of pasture associated laminitis - Longland & Byrd 2006, Watts 2004.
Grazing on pasture increases plasma insulin concentrations depending on the metabolic status of the horse - Geor 2009.
Katz & Bailey suggest that feeding inulin also increases plasma insulin concentrations in IR individuals - Bailey 2007 and Borer 2012 - but we show (below) that this cannot be concluded from either of these papers and that ESC (particularly glucose) was the more likely cause of increases in insulin concentrations in IR ponies.
de Laat's 2011 research showed that laminitic changes in the feet happen at insulin concentrations of 200 uIU/ml or lower. Walsh et al 2009 found that the onset of laminitis was associated with hyperinsulinaemia > 100 uIU/ml.
Insulin does not appear to play a role in the OF overload model (Milinovich 2006), but horses with pasture associated laminitis generally have insulin concentrations above normal, or an above normal response to a dynamic test such as the oral glucose test.
Katz and Bailey conclude "In pasture-associated laminitis, although this condition may have multiple contributors, it is highly likely that hyperinsulinaemia and/or IR play a significant role; the effects of pasture fructans being fermented in the large intestine may not be sufficient to cause laminitis without other metabolic triggers such as the additional effects of insulin." It may be that rapid fermentation of fructans contribute to the development of laminitis - but research adding 3 g/kg BW inulin making a total of 6.1 g/kg BW fructan (Bailey et al. 2007, Crawford et al. 2007) found no signs of lameness or laminitis. Bailey made no reference to any clinical symptoms being observed. Crawford made no reference to any clinical symptoms being observed, other than transient increases in digital pulse pressure in 1 or 2 limbs, a slight decrease in dung pH and increase in dung amines which could have been attributable to the sudden change of diet from hay to Readigrass.
Fructose feeding in other species contributes to IR, but there is no evidence (at the moment) that fructans are digested to fructose in the horse.
More research feeding fructans to horses:
Glatter M, Bochnia M, Goetz F, Gottschalk J, Koeller G, Mielenz N, Hillegeist D, Greef JM, Einspanier A, Zeyner A
Glycaemic and insulinaemic responses of adult healthy warm-blooded mares following feeding with Jerusalem artichoke meal
J Anim Physiol Anim Nutr (Berl). 2017 Jun;101 Suppl 1:69-78. doi: 10.1111/jpn.12669
So where did the idea that fructans might contribute to endocrine laminitis come from?
How could fructan overload lead to above normal glucose and insulin?
Bailey et al. 2007 Effect of dietary fructans and dexamethasone administration on the insulin response of ponies predisposed to laminitis
"Periods of high pasture nonstructural carbohydrate content (which includes simple sugars, starches and fructans) appear to correlate with peak periods of laminitis incidence."
How could fructan overload lead to above normal glucose and insulin?
Bailey et al. 2007 Effect of dietary fructans and dexamethasone administration on the insulin response of ponies predisposed to laminitis
"Periods of high pasture nonstructural carbohydrate content (which includes simple sugars, starches and fructans) appear to correlate with peak periods of laminitis incidence."
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In September Bailey et al. tested insulin and glucose in previously laminitic ponies (LP) and never laminitic ponies (NP) after they had been eating grass (WSC 18.2%, fructan 13.8%, ESC 4.4%) and hay (WSC 6.6%, fructan 3.4%, ESC 3.2%), and found that LP had a greater insulin response than NP to both grass and hay.
The grass appears to have been sampled before 10 am (when ESC is likely to be lower than later in the day). Presumably it is possible that ESC levels in the grass could have been considerably higher recently, and that ponies grazing high ESC grass would have correspondingly high insulin levels. No mention is made of whether the LP had regional adiposity - they were not obese but they were less insulin sensitive than the NP therefore clinical signs of EMS might be expected. EMS horses habituated to eating high NSC diets often have hyperinsulinaemia, even if fasted before the blood is drawn. 
"Grass" samples were taken as the ponies were removed from pasture. "Hay" samples were taken on day 7 of hay diet
They suggest that fructan could be a major factor in the development of hyperinsulinaemia in LP at pasture - but no explanation is given as to how, other than that fructan may be broken down by bacteria in the stomach and small intestine releasing fructose (Coenen et al 2006). Although it is suggested that fructose can lead to insulin resistance, no explanation is given for how this would lead to hyperinsulinaemia.
They show that insulin resistant ponies (LPs) secrete more insulin in response to glucose than NPs (insulin-modified IV glucose tolerance test), and that fructose tends to cause less of an insulin response to glucose. We know that insulin resistant ponies have a greater insulin response to glucose than normal ponies - this would appear to explain every finding in this research. More.. |
In March LP and NP ponies were stabled and fed hay for 2 weeks, then had their diet abruptly changed to 2/3 hay and 1/3 Readigrass - a freeze-dried perennial ryegrass which is high in sugars and fructan and “has an energy level equivalent to cereals or medium energy compounds” according to Spiller’s website - plus 3 g/kg (bw) inulin, a form of shorter-chain fructan, fed in 3 meals/day, which increased the total fructan in the diet from 4.1 g/kg (bw) to 6.1 g/kg (bw). These figures seem a little surprising - 4.1 g/kg bw fructan would be the equivalent of a 20.5% fructan hay for a 500 kg horse eating 2% bw/d - this is very high - a quick look through many hay analyses carried out by Equi-Analytical with hay samples from the UK, Canada and USA showed that the highest fructan % DM was less than 15% DM, most were below 10% DM. It then seems odd that adding 3 g/kg (bw) fructan plus a supposedly high fructan freeze-dried ryegrass only increased the fructan in the second diet by 2 g/kg (bw).
Again, LP had a greater insulin response to both hay, and hay with Readigrass and inulin, than NP. No ponies showed any signs of laminitis or lameness. No mention is made of any pony having diarrhoea or showing increased heart rate, respiration rate or temperature. Bailey et al. conclude that the LP had an exaggerated response to fructans - how can this conclusion be made? No controls were used - i.e. no horses were given the 2/3 hay 1/3 Readigrass diet without the inulin (fructan), therefore it is surely impossible to correlate any response to the inulin (fructan). All that can be concluded is that previously laminitic ponies, who were less insulin sensitive, had a greater insulin response to all diets, than never laminitic ponies. 
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Crawford et al 2007 followed the same protocol as Bailey - normal ponies (NP) and laminitis-prone ponies (LP) were stalled and fed hay with a fructan level of 4.3 g/kg BW for 2 weeks, then for the third week the diet was abruptly changed from 100% hay to 2/3 hay and 1/3 Readigrass (a freeze-dried ryegrass with high sugar and fructan levels and the equivalent of a medium energy feed according to Spillers) plus 3 g/kg BW inulin (DP 2-60), giving a total fructan content of 6.15 g/kg BW/d, divided into 3 meals. Again there were no controls - no ponies were fed Readigrass without inulin - therefore results recorded could be attributed to either the Readigrass or the inulin. Blood and dung was tested on the hay diet and 1, 2, 3 and 5 days after changing onto the Readigrass and inulin diet, at 5 pm - 1 hr after being fed (Borer et al 2012 found insulin peaked 2 - 4 hrs after ponies were fed). Insulin and glucose were not tested.
No pony showed any signs of laminitis or lameness, and there was no difference in hoof wall surface temperature with diet or between groups. No changes to plasma lactate (so intestinal mucosa not compromised), no clinical symptoms, no change in plasma amines, slight increase in amines in dung with Readigrass/inulin diet (amines are produced when dietary protein is fermented in the large intestine, Readigrass is a high protein feed), slight decrease in faecal pH from 6.89 to 6.18 after 2 days on the Readigrass/inulin diet which rose slightly but remained below the hay only pH.
Crawford et al. concluded that the addition of fructan resulted in decreased dung pH and increased bacterial production of amines. However, with no control horses fed Readigrass without inulin, these changes surely cannot be attributed to the insulin/fructan, and could have been caused by changing 1/3 of the diet suddenly from hay to Readigrass, a high sugar, high protein feed. The paper states “This indicates that the threshold for inulin inclusion, at which point hindgut alterations lead to significant leakage of these factors into the circulation, is somewhat above 3 g/kg of BW” - but see below - these ponies actually ate 6.1 g/kg BW fructan per day with no symptoms of illness.
More..
What these 2 papers from 2007 do appear to show us is that ponies, both never laminitic and previously laminitic, ate 6.1 g/kg BW fructan per day, split into 3 feedings, for a week, with no signs of lameness or laminitis, presumably no diarrhoea or increased heart rate, respiration rate or temperature, just a slight decrease in faecal pH (Crawford et al. 2007) on day 2 of inulin feeding which started to rise from day 3. 6.1 g/kg BW/day is more than the 5 g/kg BW used by Kalck et al 2009 which induced laminitis in 3 out of 8 horses, but which was administered all in one go straight into the stomach by nasogastric tube - which could not happen under normal eating conditions. Assuming a horse is eating 2% of its bodyweight/day, 6.1 g/kg BW would be 3,050 g fructan, or a 30.5% fructan grass or hay. Yes, grass is seen with fructan levels this high and higher - but looking at average grass samples, most grass appears to contain considerably less fructan than 30%. Fructan and sugar levels change throughout the day - the levels that tend to get reported are likely to be the peaks - during the night and early hours of the morning, sugar and fructan levels will generally be considerably lower than peak levels. Also grass that is stressed and therefore storing fructans is quite likely to be short - it is likely that it will be harder for horses to eat large quantities of it, than lusher faster growing grass.
In 2012 Borer et al 2012 showed that feeding glucose significantly increases the insulin response, feeding inulin (fructan) doesn't - and a control was used. 7 normal (NP) and 5 previously laminitic ponies (PLP) were fed hay (baseline), Happy Hoof (control), and Happy Hoof plus 1 g/kg glucose (Dextrose monohydrate), 1 g/kg BW fructose and 1 g/kg BW inulin (Orafti inulin - a mix of oligo- and polysaccharides with beta-1,2 bonds with DP 3 to 60, extracted from chicory root) for 3 days after being at pasture (but brought into barn with hay the day before testing) or in a barn with timothy hay for 7+ days in May-June and Oct-Nov. Blood was tested before and for 12 hrs after feeding.
No clinical signs of laminitis were seen at any point, the only adverse effect noted was 1 PLP had softened faeces when fed fructose but no signs of abdominal pain were seen.
Note: ponies showed no clinical symptoms of PPID and tested negative to DST, but ACTH was not tested.
Horses at grass would presumably have had more exercise than horses in barn/on hay.
Results are median, i.e. the middle result, rather than the average, and only 7 NP and 5 PLP so very small numbers.
Pasture NSC was not analysed.
Insulin sensitivity was not established.
Note also with all of the above experiments that making sudden changes to the diet may not represent "real life", and that many factors have to be considered, e.g. active transporters for glucose and fructose in the small intestine (SGLT1, GLUT5, GLUT2) may not be sufficient to absorb all sugars following a sudden change, but may adapt with time/slow introduction.
No pony showed any signs of laminitis or lameness, and there was no difference in hoof wall surface temperature with diet or between groups. No changes to plasma lactate (so intestinal mucosa not compromised), no clinical symptoms, no change in plasma amines, slight increase in amines in dung with Readigrass/inulin diet (amines are produced when dietary protein is fermented in the large intestine, Readigrass is a high protein feed), slight decrease in faecal pH from 6.89 to 6.18 after 2 days on the Readigrass/inulin diet which rose slightly but remained below the hay only pH.
Crawford et al. concluded that the addition of fructan resulted in decreased dung pH and increased bacterial production of amines. However, with no control horses fed Readigrass without inulin, these changes surely cannot be attributed to the insulin/fructan, and could have been caused by changing 1/3 of the diet suddenly from hay to Readigrass, a high sugar, high protein feed. The paper states “This indicates that the threshold for inulin inclusion, at which point hindgut alterations lead to significant leakage of these factors into the circulation, is somewhat above 3 g/kg of BW” - but see below - these ponies actually ate 6.1 g/kg BW fructan per day with no symptoms of illness.
More..
What these 2 papers from 2007 do appear to show us is that ponies, both never laminitic and previously laminitic, ate 6.1 g/kg BW fructan per day, split into 3 feedings, for a week, with no signs of lameness or laminitis, presumably no diarrhoea or increased heart rate, respiration rate or temperature, just a slight decrease in faecal pH (Crawford et al. 2007) on day 2 of inulin feeding which started to rise from day 3. 6.1 g/kg BW/day is more than the 5 g/kg BW used by Kalck et al 2009 which induced laminitis in 3 out of 8 horses, but which was administered all in one go straight into the stomach by nasogastric tube - which could not happen under normal eating conditions. Assuming a horse is eating 2% of its bodyweight/day, 6.1 g/kg BW would be 3,050 g fructan, or a 30.5% fructan grass or hay. Yes, grass is seen with fructan levels this high and higher - but looking at average grass samples, most grass appears to contain considerably less fructan than 30%. Fructan and sugar levels change throughout the day - the levels that tend to get reported are likely to be the peaks - during the night and early hours of the morning, sugar and fructan levels will generally be considerably lower than peak levels. Also grass that is stressed and therefore storing fructans is quite likely to be short - it is likely that it will be harder for horses to eat large quantities of it, than lusher faster growing grass.
In 2012 Borer et al 2012 showed that feeding glucose significantly increases the insulin response, feeding inulin (fructan) doesn't - and a control was used. 7 normal (NP) and 5 previously laminitic ponies (PLP) were fed hay (baseline), Happy Hoof (control), and Happy Hoof plus 1 g/kg glucose (Dextrose monohydrate), 1 g/kg BW fructose and 1 g/kg BW inulin (Orafti inulin - a mix of oligo- and polysaccharides with beta-1,2 bonds with DP 3 to 60, extracted from chicory root) for 3 days after being at pasture (but brought into barn with hay the day before testing) or in a barn with timothy hay for 7+ days in May-June and Oct-Nov. Blood was tested before and for 12 hrs after feeding.
No clinical signs of laminitis were seen at any point, the only adverse effect noted was 1 PLP had softened faeces when fed fructose but no signs of abdominal pain were seen.
Note: ponies showed no clinical symptoms of PPID and tested negative to DST, but ACTH was not tested.
Horses at grass would presumably have had more exercise than horses in barn/on hay.
Results are median, i.e. the middle result, rather than the average, and only 7 NP and 5 PLP so very small numbers.
Pasture NSC was not analysed.
Insulin sensitivity was not established.
Note also with all of the above experiments that making sudden changes to the diet may not represent "real life", and that many factors have to be considered, e.g. active transporters for glucose and fructose in the small intestine (SGLT1, GLUT5, GLUT2) may not be sufficient to absorb all sugars following a sudden change, but may adapt with time/slow introduction.
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Other research where horses were fed fructans
Glatter et al. 2017
Glatter et al. 2017
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So how does grass cause laminitis?
Through Insulin Resistance, or more specifically hyperinsulinaemia, which is affected by: simple sugars or ESC and probably starch in grass - specifically glucose (starch is converted to glucose in the small intestine). May be influenced by PPID and increased ACTH Aug - Oct in all horses. In addition, corticosteroids including dexamethasone increase insulin concentrations, and obesity and lack of exercise may affect insulin. Anecdotally, diarrhoea, gas colic and other abnormal signs are sometimes seen in horses grazing pasture, particularly after unusual or large ingestion of grass, e.g. if a horse escapes into a field of long grass, or following a flush of grass growth.
We know that high sugar levels precede fructan synthesis, and that SGLT1 transporters transport ingested glucose into the horse from the small intestine. Hoffman 2009 suggests that, if an increase in SGLT1 transporters lags behind an abrupt increase in sugars in the diet (as it does in mice), "sugar transport would be inadequate, thus exacerbating hydrolyzable carbohydrate overload to the hind gut" - so perhaps it is sugar reaching the hind gut that causes the clinical signs seen. |
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How much NSC/WSC/ESC/fructan is in grass?
Sugar and fructan concentrations change throughout the day and year, depending on sunlight intensity, environmental temperature, availability of water, availability of nutrients (fertilizer), stage of growth.
Grazing and mowing cause fructans to be reduced:
Howieson MJ, Christians NE
Carbohydrate Metabolism and Efficiency of Photosystem II in Mown Creeping Bentgrass (Agrostis stoloniferaL.)
HortScience April 2008vol. 43 no. 2 525-531
Grass that is analysed for fructan and sugar levels is often not grazed, therefore may not represent grass that is grazed.
McIntosh Bridgett PhD dissertation December 2006
Circadian and Seasonal Variation in Pasture Nonstructural Carbohydrates and the Physiological Response of Grazing Horses
See graphs on p50
From Longland and Byrd 2006:
WSC 95 – 560 g/kg DM of which fructan 32 – 439 g/kg DM
Higher at temps 5 – 10’C, lower at temps 15 – 25’C
Orchard grass in drought conditions in Mediterranean had fructan 350 – 400 g/kg DM in stem bases.
WSC changed from 160 – 240 g/kg within 3 hours.
Germany 10 horse farms Apr – Nov fructan ranges 18 – 57 g/kg DM – highest May, lowest Aug, intermediate Oct.
3 year study 9 sites Germany, Ireland, UK, Norway & Sweden WSC ranged < 100 g/kg to > 385 g/kg DM – highest at cooler temps. Over 2 growing seasons in UK fructan ranges 75 – 279 g/kg being 55 – 75% WSC, sucrose 16 – 22% WSC, fructose 6 – 12% WSC, glucose 3 – 10% WSC.
Simple sugars recorded up to 10% DM.
Equi-Analytical has average grass pasture (which is likely to include C3 and C4):
WSC range 4.62 – 15.97%
ESC range 3.61 – 10.97%
Therefore fructans range 1.01 – 5.0 %
Bailey et al 2007 September grass:
ESC 44 g/kg DM
Fructan 138 g/kg DM
WSC 182 g/kg DM
By comparison, timothy hay:
ESC 32 g/kg DM
Fructan 34 g/kg DM
WSC 66 g/kg DM
Effects of PPID, season and pasture diet on blood, ACTH and metabolite concentrations in horses - Sarah Elliott
Grass samples from Tennessee latitude 35 (so likely C4 > C3 (C4 becomes dominant at around 40 - 45' latitutude)?), taken from wire exclusion cages, collected 9 - 10 am, stems cut 1 cm above ground, ice packed then stored at -20'C. Analysed by Dairy One wet chemistry:
ESC ranged 2.0 to 9.1%
WSC ranged 1.6 to 12.7% (WSC cannot be less than ESC - therefore this must be testing variance).
Therefore fructan ranged 0 to 3.6%
Starch ranged 1.0 - 2.0%
Ince et al. 2005 In vitro fermentation of three species of fresh grass differing in water soluble carbohydrate content with an equine faecal inoculum - all figures DM:
Timothy WSC 215 g/kg, 164 g/kg fructan, 51 g/kg ESC
Cocksfoot WSC 258 g/kg, 179 g/kg fructan, 79 g/kg ESC
Perennial ryegrass WSC 349 g/kg, 185 g/kg fructan, 164 g/kg ESC
Ince JC, Longland AC, Moore-Colyer MJS, Preservation of Timothy, meadow fescue and two varieties of perennial ryegrass as hay: effect on nutrient content.
Grasses sown in April were cut 5 cm above soil level in August and analysed. All figures DM.
perennial ryegrass (Lolium perenne) 1 WSC 165 g/kg
perennial ryegrass (Lolium perenne) 2 WSC 113 g/kg
meadow fescue (Festuca pretensis) WSC 48 g/kg
timothy (Phleum pretense) WSC 83 g/kg
Longland et al 2012 - pasture contains varying amounts (0 to ≥ 200 g kg DM) fructans. Fructans in 4 species (Phleum pretense, Festuca rubra, Dactylis glomerata, Lolium perenne) managed for grazing and sampled April to November and managed for conservation and sampled in July ranged from 83 to 299 g/kg DM (HPLC) with an average of 154 g/kg. Analysis by colorimetric methods, considered not as accurate, found fructan levels of 5 to 238 g/kg DM.
Annette Longland Nutritional assessment of forage quality - Forages and Grazing in Horse Nutrition 2012
WSC content of perennial ryegrass (Lolium perenne) DM:
Early May (Green et al 1971) - vegetative 100 g/kg
Late May (Green et al 1971) - elongation/early reproductive 150 g/kg
Early June (Green et al 1971) - seed set/development 200 g/kg
July (Slepetys 2001) - seed ripened (stems) 76 g/kg
WSC in perennial ryegrass in full sun on a spring day rose from 250 g/kg at 5 am to 310 g/kg at 1-3 pm declining to 180 g/kg by 11 pm (Longland 2005).
Average WSC of 8 perennial ryegrass varieties managed for grazing by regular cutting over 2 years (Longland 2005) in g/kg DM:
early April 186
end April 166
mid May 235
early June 165
early July 205
early Aug 158
early Sept 211
early Oct 161
MAFF 1992 late spring/early summer pasture WSC content can approach 300 g/kg WM, although levels of 200 - 220 g/kg DM WSC may be more usual.
What about fructans in hay?
As soon as grass is cut for hay it starts to lose sugar, due to respiration (carbohydrates are converted to water and carbon dioxide). Respiration will continue until the grass is less than 40% moisture - the longer hay takes to dry, the more non-structural carbohydrates are lost.
Animal Nutrition 7th Edition (Google this to find the .pdf)
Peter McDonald, J.F.D. Greenhalgh, C A Morgan, R Edwards, Liam Sinclair,Robert Wilkinson
Ould-Ahmed M, Decau M-L, Morvan-Bertrand A, Prud'homme M-P, Lafrenière C, Drouin P
Fructan, sucrose and related enzyme activities are preserved in timothy (Phleum pratense L.) during wilting
Grass Forage Sci 2017, 72: 64–79. doi:10.1111/gfs.12209
Timothy grass was cut and wilted for 24 hours at 15'C or 20'C in either darkness or light. Soluble protein, glucose and starch contents decreased, amino acid, sucrose and fructose contents increased, and fructan content was unchanged.
There IS sugar in grass and hay - Katy Watts www.safergrass.org
Müller C E, Von Rosen D, Udén P
Effect of forage conservation method on microbial flora and fermentation pattern in forage and in equine colon and faeces
Livestock Science Volume 119, Issues 1–3, December 2008, Pages 116–128
WSC in grass is reduced by respiration and hydrolysis after cutting (Lundén Pettersson & Lindgren, 1989, McDonald et al. 2002). Fructan may be hydrolysed to fructose (McDonald et al. 2002). Wylam (1953) found that 64% of fructan was broken down by the time the dry matter content of grass reached 78%.
Sugar and fructan concentrations change throughout the day and year, depending on sunlight intensity, environmental temperature, availability of water, availability of nutrients (fertilizer), stage of growth.
Grazing and mowing cause fructans to be reduced:
Howieson MJ, Christians NE
Carbohydrate Metabolism and Efficiency of Photosystem II in Mown Creeping Bentgrass (Agrostis stoloniferaL.)
HortScience April 2008vol. 43 no. 2 525-531
Grass that is analysed for fructan and sugar levels is often not grazed, therefore may not represent grass that is grazed.
McIntosh Bridgett PhD dissertation December 2006
Circadian and Seasonal Variation in Pasture Nonstructural Carbohydrates and the Physiological Response of Grazing Horses
See graphs on p50
From Longland and Byrd 2006:
WSC 95 – 560 g/kg DM of which fructan 32 – 439 g/kg DM
Higher at temps 5 – 10’C, lower at temps 15 – 25’C
Orchard grass in drought conditions in Mediterranean had fructan 350 – 400 g/kg DM in stem bases.
WSC changed from 160 – 240 g/kg within 3 hours.
Germany 10 horse farms Apr – Nov fructan ranges 18 – 57 g/kg DM – highest May, lowest Aug, intermediate Oct.
3 year study 9 sites Germany, Ireland, UK, Norway & Sweden WSC ranged < 100 g/kg to > 385 g/kg DM – highest at cooler temps. Over 2 growing seasons in UK fructan ranges 75 – 279 g/kg being 55 – 75% WSC, sucrose 16 – 22% WSC, fructose 6 – 12% WSC, glucose 3 – 10% WSC.
Simple sugars recorded up to 10% DM.
Equi-Analytical has average grass pasture (which is likely to include C3 and C4):
WSC range 4.62 – 15.97%
ESC range 3.61 – 10.97%
Therefore fructans range 1.01 – 5.0 %
Bailey et al 2007 September grass:
ESC 44 g/kg DM
Fructan 138 g/kg DM
WSC 182 g/kg DM
By comparison, timothy hay:
ESC 32 g/kg DM
Fructan 34 g/kg DM
WSC 66 g/kg DM
Effects of PPID, season and pasture diet on blood, ACTH and metabolite concentrations in horses - Sarah Elliott
Grass samples from Tennessee latitude 35 (so likely C4 > C3 (C4 becomes dominant at around 40 - 45' latitutude)?), taken from wire exclusion cages, collected 9 - 10 am, stems cut 1 cm above ground, ice packed then stored at -20'C. Analysed by Dairy One wet chemistry:
ESC ranged 2.0 to 9.1%
WSC ranged 1.6 to 12.7% (WSC cannot be less than ESC - therefore this must be testing variance).
Therefore fructan ranged 0 to 3.6%
Starch ranged 1.0 - 2.0%
Ince et al. 2005 In vitro fermentation of three species of fresh grass differing in water soluble carbohydrate content with an equine faecal inoculum - all figures DM:
Timothy WSC 215 g/kg, 164 g/kg fructan, 51 g/kg ESC
Cocksfoot WSC 258 g/kg, 179 g/kg fructan, 79 g/kg ESC
Perennial ryegrass WSC 349 g/kg, 185 g/kg fructan, 164 g/kg ESC
Ince JC, Longland AC, Moore-Colyer MJS, Preservation of Timothy, meadow fescue and two varieties of perennial ryegrass as hay: effect on nutrient content.
Grasses sown in April were cut 5 cm above soil level in August and analysed. All figures DM.
perennial ryegrass (Lolium perenne) 1 WSC 165 g/kg
perennial ryegrass (Lolium perenne) 2 WSC 113 g/kg
meadow fescue (Festuca pretensis) WSC 48 g/kg
timothy (Phleum pretense) WSC 83 g/kg
Longland et al 2012 - pasture contains varying amounts (0 to ≥ 200 g kg DM) fructans. Fructans in 4 species (Phleum pretense, Festuca rubra, Dactylis glomerata, Lolium perenne) managed for grazing and sampled April to November and managed for conservation and sampled in July ranged from 83 to 299 g/kg DM (HPLC) with an average of 154 g/kg. Analysis by colorimetric methods, considered not as accurate, found fructan levels of 5 to 238 g/kg DM.
Annette Longland Nutritional assessment of forage quality - Forages and Grazing in Horse Nutrition 2012
WSC content of perennial ryegrass (Lolium perenne) DM:
Early May (Green et al 1971) - vegetative 100 g/kg
Late May (Green et al 1971) - elongation/early reproductive 150 g/kg
Early June (Green et al 1971) - seed set/development 200 g/kg
July (Slepetys 2001) - seed ripened (stems) 76 g/kg
WSC in perennial ryegrass in full sun on a spring day rose from 250 g/kg at 5 am to 310 g/kg at 1-3 pm declining to 180 g/kg by 11 pm (Longland 2005).
Average WSC of 8 perennial ryegrass varieties managed for grazing by regular cutting over 2 years (Longland 2005) in g/kg DM:
early April 186
end April 166
mid May 235
early June 165
early July 205
early Aug 158
early Sept 211
early Oct 161
MAFF 1992 late spring/early summer pasture WSC content can approach 300 g/kg WM, although levels of 200 - 220 g/kg DM WSC may be more usual.
What about fructans in hay?
As soon as grass is cut for hay it starts to lose sugar, due to respiration (carbohydrates are converted to water and carbon dioxide). Respiration will continue until the grass is less than 40% moisture - the longer hay takes to dry, the more non-structural carbohydrates are lost.
Animal Nutrition 7th Edition (Google this to find the .pdf)
Peter McDonald, J.F.D. Greenhalgh, C A Morgan, R Edwards, Liam Sinclair,Robert Wilkinson
Ould-Ahmed M, Decau M-L, Morvan-Bertrand A, Prud'homme M-P, Lafrenière C, Drouin P
Fructan, sucrose and related enzyme activities are preserved in timothy (Phleum pratense L.) during wilting
Grass Forage Sci 2017, 72: 64–79. doi:10.1111/gfs.12209
Timothy grass was cut and wilted for 24 hours at 15'C or 20'C in either darkness or light. Soluble protein, glucose and starch contents decreased, amino acid, sucrose and fructose contents increased, and fructan content was unchanged.
There IS sugar in grass and hay - Katy Watts www.safergrass.org
Müller C E, Von Rosen D, Udén P
Effect of forage conservation method on microbial flora and fermentation pattern in forage and in equine colon and faeces
Livestock Science Volume 119, Issues 1–3, December 2008, Pages 116–128
WSC in grass is reduced by respiration and hydrolysis after cutting (Lundén Pettersson & Lindgren, 1989, McDonald et al. 2002). Fructan may be hydrolysed to fructose (McDonald et al. 2002). Wylam (1953) found that 64% of fructan was broken down by the time the dry matter content of grass reached 78%.
How reliable is fructan analysis?
Wet chemistry analysis is the most accurate. NIR gives an estimate according to calibration against wet chemistry results.
Testing for sugar/starch in feeds - Katy Watts - www.safergrass.org
According to Katy Watts, wet chemistry, as carried out by Equi-Analytical/Diary One (for some of their analyses - not all) is the most accurate method of analysing WSC, ESC (and therefore fructan = WSC - ESC) and starch.
Longland et al 2012 compared fructan analysis by high-performance liquid chromatography (HPLC), used for research purposes, and a comercially available colorimetric method and found that the colormetric method understated total fructan content - 83 - 299 g/kg DM HPLC compared to 5 - 238 g/kg DM colormetric.
Wet chemistry analysis is the most accurate. NIR gives an estimate according to calibration against wet chemistry results.
Testing for sugar/starch in feeds - Katy Watts - www.safergrass.org
According to Katy Watts, wet chemistry, as carried out by Equi-Analytical/Diary One (for some of their analyses - not all) is the most accurate method of analysing WSC, ESC (and therefore fructan = WSC - ESC) and starch.
Longland et al 2012 compared fructan analysis by high-performance liquid chromatography (HPLC), used for research purposes, and a comercially available colorimetric method and found that the colormetric method understated total fructan content - 83 - 299 g/kg DM HPLC compared to 5 - 238 g/kg DM colormetric.
How much fructan could horses consume?
Crawford et al 2007: It has been calculated from some studies of pasture consumption (Longland and Byrd, 2006) that horses can commonly consume between 2.1 and 3.5 kg of fructans per d (4.2 to 7.0 g/kg of BW) for a 500-kg animal. This calculation was based on DM intakes of between 1.5 and 3% of BW per day, and a peak fructan content of around 25 to 30% of DM, although greater DM intakes have been reported (Longland and Byrd, 2006). Therefore, even at the lower end of this range of DM intakes, the total intake of fructan at certain times of the year on certain pastures could be considerable.
Annette Longland presented at the Equine Science Society 2011: mature ponies not in work ate an average of 3.8% BW DM mixed grass/legume pasture over 6 weeks - from 3.4% BW higher quality pasture (DE 2.9 Mcal/kg) to 4.2% lower quality pasture (DE 2.3 Mcal/kg) - however, these were estimated figures calculated from changes in body weight.
The NRC 2007 suggests an intake of 2 - 2.55 % BW/d for grazing adult non-lactating horses.
Under some circumstances around 5% BW/d has been reported - see
Smith et al 2007
Longland et al 2011
Pratt-Phillips et al 2011
Voluntary DM intakes of fresh forages by horses and ponies have been measured and values ranging from 1.5 - 5.2% BW/d reported - Marlow et al 1983 & as above. Higher values tend to be ponies. Horses are regarded as averaging 2.2% BW/d for mature horses and 2.5 - 3% BW/d for lactating mares.
Martinson KL, Siciliano PD, Sheaffer CC, McIntosh BJ, Swinker AM, Williams CA
A Review of Equine Grazing Research Methodologies
JEVS published online 14 January 2017
Crawford et al 2007: It has been calculated from some studies of pasture consumption (Longland and Byrd, 2006) that horses can commonly consume between 2.1 and 3.5 kg of fructans per d (4.2 to 7.0 g/kg of BW) for a 500-kg animal. This calculation was based on DM intakes of between 1.5 and 3% of BW per day, and a peak fructan content of around 25 to 30% of DM, although greater DM intakes have been reported (Longland and Byrd, 2006). Therefore, even at the lower end of this range of DM intakes, the total intake of fructan at certain times of the year on certain pastures could be considerable.
Annette Longland presented at the Equine Science Society 2011: mature ponies not in work ate an average of 3.8% BW DM mixed grass/legume pasture over 6 weeks - from 3.4% BW higher quality pasture (DE 2.9 Mcal/kg) to 4.2% lower quality pasture (DE 2.3 Mcal/kg) - however, these were estimated figures calculated from changes in body weight.
The NRC 2007 suggests an intake of 2 - 2.55 % BW/d for grazing adult non-lactating horses.
Under some circumstances around 5% BW/d has been reported - see
Smith et al 2007
Longland et al 2011
Pratt-Phillips et al 2011
Voluntary DM intakes of fresh forages by horses and ponies have been measured and values ranging from 1.5 - 5.2% BW/d reported - Marlow et al 1983 & as above. Higher values tend to be ponies. Horses are regarded as averaging 2.2% BW/d for mature horses and 2.5 - 3% BW/d for lactating mares.
Martinson KL, Siciliano PD, Sheaffer CC, McIntosh BJ, Swinker AM, Williams CA
A Review of Equine Grazing Research Methodologies
JEVS published online 14 January 2017
Conclusion
References:
Asplin KE, Sillence MN, Pollitt CC, McGowan CM
Induction of laminitis by prolonged hyperinsulinaemia in clinically normal ponies
The Veterinary Journal Vol 174, Issue 3, November 2007, Pages 530-535
Borer KE, Bailey SR, Menzies-Gow NJ, Harris PA, Elliott J
Effect of feeding glucose, fructose, and inulin on blood glucose and insulin concentrations in normal ponies and those predisposed to laminitis
J Anim Sci. 2012 Sep;90(9):3003-11. doi: 10.2527/jas.2011-4236
Comment..
Coenen M, Mößeler A, Vervuert I
Fermentative Gases in Breath Indicate that Inulin and Starch Start to Be Degraded by Microbial Fermentation in the Stomach and Small Intestine of the Horse in Contrast to Pectin and CelluloseJ. Nutr. July 2006 vol. 136no. 7 2108S-2110S
Crawford C, Sepulveda MF, Elliott J, Harris PA, Bailey SR
Dietary fructan carbohydrate increases amine production in the equine large intestine: Implications for pasture-associated laminitis
J ANIM SCI November 2007 vol. 85 no. 11 2949-2958
Comment..
de Laat MA, Kyaw-Tanner MT, Nourian AR, McGowan CM, Sillence MN, Pollitt CC
The developmental and acute phases of insulin-induced laminitis involve minimal metalloproteinase activity
Veterinary ImmunologyandImmunopathology 140 (2011) 275–281
de Laat M, Sillence M, McGowan C, Pollitt C
Insulin-Induced Laminitis - An investigation of the disease mechanism in horses
RIRDC Dec 2011
Elliott Sarah B, MSc thesis, University of Tennessee December 2010
Effects of PPID, season and pasture diet on blood, ACTH and metabolite concentrations in horses
Comment..
(Published as:) Frank N, Elliott SB, Chameroy KA, Tóth F, Chumbler NS, McClamroch R
Association of season and pasture grazing with blood hormone and metabolite concentrations in horses with presumed pituitary pars intermedia dysfunction.
J Vet Intern Med. 2010 Sep-Oct;24(5):1167-75.
Gallagher JA, Cairns AJ, Thomas D, Charlton A, Williams P, Turner LB
Fructan synthesis, accumulation, and polymer traits. I. Festulolium chromosome substitution lines
Front. Plant Sci. 08 July 2015. https://doi.org/10.3389/fpls.2015.00486
Geor RJ
Digestive strategy and flexibility in horses with reference to dietary carbohydrates
5th European Workshop Equine Nutrition 2010 p17
Glatter M, Bochnia M, Goetz F, Gottschalk J, Koeller G, Mielenz N, Hillegeist D, Greef JM, Einspanier A, Zeyner A
Glycaemic and insulinaemic responses of adult healthy warm-blooded mares following feeding with Jerusalem artichoke meal
J Anim Physiol Anim Nutr (Berl). 2017 Jun;101 Suppl 1:69-78. doi: 10.1111/jpn.12669
Hoffman RM
Carbohydrate metabolism and metabolic disorders in horses
R. Bras. Zootec. vol.38 no.spe Viçosa July 2009
Ince JC, Longland AC, Moore-Colyer MJS, Harris PA
In vitro degradation of grass fructan by equid gastrointestinal digesta
Grass and Forage Science published online 08 June 2013
Karen A. Kalck, Nicholas Frank, Sarah B. Elliott, Raymond C. Boston
Effects of low-dose oligofructose treatment administered via nasogastric intubation on induction of laminitis and associated alterations in glucose and insulin dynamics in horses
American Journal of Veterinary Research 2009 70:5, 624-632
Katz LM and Bailey SR
A review of recent advances and current hypothesis on the pathogenesis of laminitis
Equine Veterinary Journal Volume 44, Issue 6, pages 752–761, November 2012
Keller MD, Pollitt CC, Marx UC
Nuclear magnetic resonance-based metabonomic study of early time point laminitis in an oligofructose-overload model
Equine Vet J. 2011 Nov;43(6):737-43
Longland AC, Ince JC, Moore-Colyer MJS, Harris PA
Degradation of grass and grass fructan by equine gastrointestinal digesta in vitro
p 107 Forages and Grazing in Horse Nutrition 2012
Longland AC, Dhanoa MS, Harris PA.
Comparison of a colorimetric and a high-performance liquid chromatography method for the determination of fructan in pasture grasses for horses.
J Sci Food Agric. 2012 Jul;92(9):1878-85
Mackie RI and Wilkins CA
Enumeration of Anaerobic Bacterial Microflora of the Equine Gastrointestinal Tract
Applied and Environmental Microbiology Sept 1988, p 2155-2160
Martinson KL, Siciliano PD, Sheaffer CC, McIntosh BJ, Swinker AM, Williams CA
A Review of Equine Grazing Research Methodologies
JEVS published online 14 January 2017
McIntosh Bridgett PhD dissertation December 2006
Circadian and Seasonal Variation in Pasture Nonstructural Carbohydrates and the Physiological Response of Grazing Horses
Milinovich GJ, Trott DJ, Burrell PC, van Eps AW, Thoefner MB, Blackall LL, Al Jassim RA, Morton JM, Pollitt CC
Changes in equine hindgut bacterial populations during oligofructose-induced laminitis
Environ Microbiol. 2006 May;8(5):885-98
Milinovich GJ, Burrell PC, Pollitt CC, Klieve AV, Blackall LL, Ouwerkerk D, Woodland E, Trott DJ
Microbial ecology of the equine hindgut during oligofructose-induced laminitis
The ISME Journal (2008), 1–12
Pollitt CC, Kyaw-Tanner M, French KR, Van Eps AW, Hendrikz JK, Daradka M
Equine Laminitis
AAEP 2003
Tóth F, Frank N, Geor RJ, Boston RC
Effects of pretreatment with dexamethasone or levothyroxine sodium on endotoxin-induced alterations in glucose and insulin dynamics in horses
Am J Vet Res. 2010 Jan;71(1):60-8
TÓTH, F., FRANK, N., CHAMEROY, K. A. and BOSTON, R. C.
Effects of endotoxaemia and carbohydrate overload on glucose and insulin dynamics and the development of laminitis in horses
Equine Veterinary Journal 2009 41: 852–858
Tóth F, Frank N, Elliott SB, Geor RJ, Boston RC.
Effects of an intravenous endotoxin challenge on glucose and insulin dynamics in horses
Am J Vet Res. 2008 Jan;69(1):82-8
Treiber KH, Kronfeld DS, Hess TM, Byrd BM, Splan RK, Staniar WB
Evaluation of genetic and metabolic predispositions and nutritional risk factors for pasture-associated laminitis in ponies
J Am Vet Med Assoc. 2006 May 15;228(10):1538-45
Van Eps AW, Pollitt CC
Equine laminitis induced with oligofructoseEquine Vet J. 2006 May;38(3):203-8
Van Eps AW, Pollitt CC
Equine laminitis model: Cryotherapy reduces the severity of lesions evaluated seven days after induction with oligofructose
Equine vet. J. (2009) 41 (8) 741-746
Virkajarvi P, Saarijarvi K, Rinne M, Saastamoinen M
Grass physiology and its relation to nutritive value in feeding horses
Forages and Grazing in Horse Nutrition 2012
Vosmer J, Liesegang A, Wanner M, Zeyner A, Suter D, Hoelzle L, Wichert B
Fermentation of six different forages in the semi-continuous fermentation technique Caesitec
Journal of Animal Physiology and Animal Nutrition 2012, 96: 860–869. doi:10.1111/j.1439-0396.2011.01269.x
Walsh DM, McGowan CM, McGowan T, Lamb SV, Schanbacher BJ, Place NJ
Correlation of Plasma Insulin Concentration with Laminitis Score in a Field Study of Equine Cushing’s Disease and Equine Metabolic Syndrome
Journal of Equine Veterinary Science Vol 29, No 2 (2009)
Asplin KE, Sillence MN, Pollitt CC, McGowan CM
Induction of laminitis by prolonged hyperinsulinaemia in clinically normal ponies
The Veterinary Journal Vol 174, Issue 3, November 2007, Pages 530-535
Borer KE, Bailey SR, Menzies-Gow NJ, Harris PA, Elliott J
Effect of feeding glucose, fructose, and inulin on blood glucose and insulin concentrations in normal ponies and those predisposed to laminitis
J Anim Sci. 2012 Sep;90(9):3003-11. doi: 10.2527/jas.2011-4236
Comment..
Coenen M, Mößeler A, Vervuert I
Fermentative Gases in Breath Indicate that Inulin and Starch Start to Be Degraded by Microbial Fermentation in the Stomach and Small Intestine of the Horse in Contrast to Pectin and CelluloseJ. Nutr. July 2006 vol. 136no. 7 2108S-2110S
Crawford C, Sepulveda MF, Elliott J, Harris PA, Bailey SR
Dietary fructan carbohydrate increases amine production in the equine large intestine: Implications for pasture-associated laminitis
J ANIM SCI November 2007 vol. 85 no. 11 2949-2958
Comment..
de Laat MA, Kyaw-Tanner MT, Nourian AR, McGowan CM, Sillence MN, Pollitt CC
The developmental and acute phases of insulin-induced laminitis involve minimal metalloproteinase activity
Veterinary ImmunologyandImmunopathology 140 (2011) 275–281
de Laat M, Sillence M, McGowan C, Pollitt C
Insulin-Induced Laminitis - An investigation of the disease mechanism in horses
RIRDC Dec 2011
Elliott Sarah B, MSc thesis, University of Tennessee December 2010
Effects of PPID, season and pasture diet on blood, ACTH and metabolite concentrations in horses
Comment..
(Published as:) Frank N, Elliott SB, Chameroy KA, Tóth F, Chumbler NS, McClamroch R
Association of season and pasture grazing with blood hormone and metabolite concentrations in horses with presumed pituitary pars intermedia dysfunction.
J Vet Intern Med. 2010 Sep-Oct;24(5):1167-75.
Gallagher JA, Cairns AJ, Thomas D, Charlton A, Williams P, Turner LB
Fructan synthesis, accumulation, and polymer traits. I. Festulolium chromosome substitution lines
Front. Plant Sci. 08 July 2015. https://doi.org/10.3389/fpls.2015.00486
Geor RJ
Digestive strategy and flexibility in horses with reference to dietary carbohydrates
5th European Workshop Equine Nutrition 2010 p17
Glatter M, Bochnia M, Goetz F, Gottschalk J, Koeller G, Mielenz N, Hillegeist D, Greef JM, Einspanier A, Zeyner A
Glycaemic and insulinaemic responses of adult healthy warm-blooded mares following feeding with Jerusalem artichoke meal
J Anim Physiol Anim Nutr (Berl). 2017 Jun;101 Suppl 1:69-78. doi: 10.1111/jpn.12669
Hoffman RM
Carbohydrate metabolism and metabolic disorders in horses
R. Bras. Zootec. vol.38 no.spe Viçosa July 2009
Ince JC, Longland AC, Moore-Colyer MJS, Harris PA
In vitro degradation of grass fructan by equid gastrointestinal digesta
Grass and Forage Science published online 08 June 2013
Karen A. Kalck, Nicholas Frank, Sarah B. Elliott, Raymond C. Boston
Effects of low-dose oligofructose treatment administered via nasogastric intubation on induction of laminitis and associated alterations in glucose and insulin dynamics in horses
American Journal of Veterinary Research 2009 70:5, 624-632
Katz LM and Bailey SR
A review of recent advances and current hypothesis on the pathogenesis of laminitis
Equine Veterinary Journal Volume 44, Issue 6, pages 752–761, November 2012
Keller MD, Pollitt CC, Marx UC
Nuclear magnetic resonance-based metabonomic study of early time point laminitis in an oligofructose-overload model
Equine Vet J. 2011 Nov;43(6):737-43
Longland AC, Ince JC, Moore-Colyer MJS, Harris PA
Degradation of grass and grass fructan by equine gastrointestinal digesta in vitro
p 107 Forages and Grazing in Horse Nutrition 2012
Longland AC, Dhanoa MS, Harris PA.
Comparison of a colorimetric and a high-performance liquid chromatography method for the determination of fructan in pasture grasses for horses.
J Sci Food Agric. 2012 Jul;92(9):1878-85
Mackie RI and Wilkins CA
Enumeration of Anaerobic Bacterial Microflora of the Equine Gastrointestinal Tract
Applied and Environmental Microbiology Sept 1988, p 2155-2160
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