U V W X Y Z
Urinary cortisol:creatinine ratio
Vaccines
Vasoconstriction and Vasodilation
Vasopressin
Velagliflozin
Venogram
Vets
Vitex agnus castus (Chastetree berry)
Weight
Weight gain
Weight loss
White line (including white line disease)
Worms and parasites
Vaccines
Vasoconstriction and Vasodilation
Vasopressin
Velagliflozin
Venogram
Vets
Vitex agnus castus (Chastetree berry)
Weight
Weight gain
Weight loss
White line (including white line disease)
Worms and parasites
Urinary cortisol:creatinine ratio
Veterinary Record 2002;150:25 773-776
Urinary cortisol:creatinine ratios in healthy horses and horses with hyperadrenocorticism and non.adrenal disease
K. J. Chandler, R. M, Dixon
Urinary cortisol:creatinine ratios in healthy horses and horses with hyperadrenocorticism and non.adrenal disease
K. J. Chandler, R. M, Dixon
Vaccines
Equine Influenza - World Organization for Animal Health
AAEP Vaccination Guidelines - Adverse Reactions
"After receiving a vaccine(s) intramuscularly, some horses experience local muscular swelling and soreness or transient, self-limiting signs including fever, anorexia and lethargy. Severe reactions at sites of injection can be particularly troublesome, requiring prolonged treatment and convalescence. Systemic adverse reactions (such as urticaria, purpura hemorrhagica or anaphylaxis) can also occur. Other systemic adverse reactions have been anecdotally reported."
"Vaccines should always be administered by .... a veterinarian, as the possibility of adverse reactions (including anaphylaxis) exists with the administration of any vaccine."
Vaccine Reactions - Tom Schell www.thehorse.com Aug 2014
Can vaccines cause laminitis?
In Equine Laminitis (2017) edited by James Belknap, Richard Mansmann and Hans Castelijns in chapter 26 suggest that a thorough assessment of a horse's body and feet "could be helpful prior to submitting the horse to specific stressors or potential laminitis triggers such as vaccinations or glucocorticoid administration", for example in a horse that is overweight and has access to spring grass that has had a previous mild reaction to vaccinations. Andrew van Eps in chapter 21 states that vaccination administration and laminitis are associated anecdotally, particularly when an adverse reaction to a vaccine has been seen.
According to an article in Horse Journal (Dec 2005), vaccines can (rarely) cause anaphylaxis and laminitis, and horses with PPID or EMS may be at higher risk of developing vaccine-triggered laminitis, especially if they have a history of laminitis:
Vaccines: Minimize Reactions - www.horse-journal.com - Dec 2005
Wagner IP, Rees CA, Dunstan RW, Credille KM, Hood DM
Evaluation of systemic immunologic hyperreactivity after intradermal testing in horses with chronic laminitis
Am J Vet Res. 2003 Mar;64(3):279-83 (PubMed)
Conclusions and clinical relevance: "Results support the hypothesis that CL horses develop hyperreactivity to various antigenic stimuli, compared with responses for nonlaminitic horses. Therefore, the possibility that antigenic challenge may result in exacerbation of clinical signs of laminitis should be discussed with horse owners. Chronic laminitis should also be a consideration when a horse becomes lame following antigenic challenges."
Can vaccines aggravate chronic laminitis? - Equine Science Update
Anaphylaxis (an acute systemic allergic reaction to an antigen to which the body has become hypersensitive) can cause laminitis, and vaccines can cause anaphylaxis:
Anaphylaxis - Blackwell's Five-Minute Veterinary Consult Equine p 63
Miller RI, Wold D, Lindsay WA, Beadle RE, McClure JJ, McClure JR, McCoy DJ
Complications associated with immunotherapy of equine phycomycosis
Journal of the American Veterinary Medical Association [1983 Jun 1, 182(11):1227-1229] (PubMed)
"Follow-up immunotherapy resulted in 1 horse responding favorably. Three horses were cured of the fungal infection but developed osteitis or deep-seated laminitis".
Gershwin LJ, Netherwood KA, Norris MS, Behrens NE, Shao MX
Equine IgE responses to non-viral vaccine components
Vaccine. 2012 Dec 14;30(52):7615-20
Lumps, Bumps and Shocking Developments - Ceci Flanagan-Snow - www.horse-canada.com - May 2011
Vaccine hypersensitivity in humans
Philipp J. Fritsche, Arthur Helbling, Barbara K. Ballmer-Weber
Vaccine hypersensitivity – update and overview
SWISS MED WKLY 2010; 140(17–18):238–246
EMS and vaccinations
Elzinga S, Reedy S, Barker VD, Chambers TM, Adams AA
Humoral and cell-mediated immune responses to influenza vaccination in equine metabolic syndrome (EMS) horses
Vet Immunol Immunopathol. 2018 May;199:32-38. doi: 10.1016/j.vetimm.2018.03.009. Epub 2018 Mar 23
"While metabolic status does not influence humoral responses to an inactivated influenza vaccine in horses, horses with EMS appear to have a reduced CMI" (cell mediated immune) "response to vaccination compared to metabolically normal, non-EMS control horses."
PPID and vaccinations
Adams AA, Siard MH, Reedy SE, Grubbs S, Little MG, Little JP
Does Equine Pituitary Pars Intermedia Dysfunction Affect Immune Responses to Vaccination?
AAEP Proceedings Vol 60 2014
Equine Influenza - World Organization for Animal Health
AAEP Vaccination Guidelines - Adverse Reactions
"After receiving a vaccine(s) intramuscularly, some horses experience local muscular swelling and soreness or transient, self-limiting signs including fever, anorexia and lethargy. Severe reactions at sites of injection can be particularly troublesome, requiring prolonged treatment and convalescence. Systemic adverse reactions (such as urticaria, purpura hemorrhagica or anaphylaxis) can also occur. Other systemic adverse reactions have been anecdotally reported."
"Vaccines should always be administered by .... a veterinarian, as the possibility of adverse reactions (including anaphylaxis) exists with the administration of any vaccine."
Vaccine Reactions - Tom Schell www.thehorse.com Aug 2014
Can vaccines cause laminitis?
In Equine Laminitis (2017) edited by James Belknap, Richard Mansmann and Hans Castelijns in chapter 26 suggest that a thorough assessment of a horse's body and feet "could be helpful prior to submitting the horse to specific stressors or potential laminitis triggers such as vaccinations or glucocorticoid administration", for example in a horse that is overweight and has access to spring grass that has had a previous mild reaction to vaccinations. Andrew van Eps in chapter 21 states that vaccination administration and laminitis are associated anecdotally, particularly when an adverse reaction to a vaccine has been seen.
According to an article in Horse Journal (Dec 2005), vaccines can (rarely) cause anaphylaxis and laminitis, and horses with PPID or EMS may be at higher risk of developing vaccine-triggered laminitis, especially if they have a history of laminitis:
Vaccines: Minimize Reactions - www.horse-journal.com - Dec 2005
Wagner IP, Rees CA, Dunstan RW, Credille KM, Hood DM
Evaluation of systemic immunologic hyperreactivity after intradermal testing in horses with chronic laminitis
Am J Vet Res. 2003 Mar;64(3):279-83 (PubMed)
Conclusions and clinical relevance: "Results support the hypothesis that CL horses develop hyperreactivity to various antigenic stimuli, compared with responses for nonlaminitic horses. Therefore, the possibility that antigenic challenge may result in exacerbation of clinical signs of laminitis should be discussed with horse owners. Chronic laminitis should also be a consideration when a horse becomes lame following antigenic challenges."
Can vaccines aggravate chronic laminitis? - Equine Science Update
Anaphylaxis (an acute systemic allergic reaction to an antigen to which the body has become hypersensitive) can cause laminitis, and vaccines can cause anaphylaxis:
Anaphylaxis - Blackwell's Five-Minute Veterinary Consult Equine p 63
Miller RI, Wold D, Lindsay WA, Beadle RE, McClure JJ, McClure JR, McCoy DJ
Complications associated with immunotherapy of equine phycomycosis
Journal of the American Veterinary Medical Association [1983 Jun 1, 182(11):1227-1229] (PubMed)
"Follow-up immunotherapy resulted in 1 horse responding favorably. Three horses were cured of the fungal infection but developed osteitis or deep-seated laminitis".
Gershwin LJ, Netherwood KA, Norris MS, Behrens NE, Shao MX
Equine IgE responses to non-viral vaccine components
Vaccine. 2012 Dec 14;30(52):7615-20
Lumps, Bumps and Shocking Developments - Ceci Flanagan-Snow - www.horse-canada.com - May 2011
Vaccine hypersensitivity in humans
Philipp J. Fritsche, Arthur Helbling, Barbara K. Ballmer-Weber
Vaccine hypersensitivity – update and overview
SWISS MED WKLY 2010; 140(17–18):238–246
EMS and vaccinations
Elzinga S, Reedy S, Barker VD, Chambers TM, Adams AA
Humoral and cell-mediated immune responses to influenza vaccination in equine metabolic syndrome (EMS) horses
Vet Immunol Immunopathol. 2018 May;199:32-38. doi: 10.1016/j.vetimm.2018.03.009. Epub 2018 Mar 23
"While metabolic status does not influence humoral responses to an inactivated influenza vaccine in horses, horses with EMS appear to have a reduced CMI" (cell mediated immune) "response to vaccination compared to metabolically normal, non-EMS control horses."
PPID and vaccinations
Adams AA, Siard MH, Reedy SE, Grubbs S, Little MG, Little JP
Does Equine Pituitary Pars Intermedia Dysfunction Affect Immune Responses to Vaccination?
AAEP Proceedings Vol 60 2014
Vasoconstriction & Vasodilation
Both vasoconstriction and vasodilation have been implicated in laminitis.
49th Annual Ocala Equine Conference October 2011 Endocrinopathic Laminitis Frank N
49th Annual Ocala Equine Conference October 2011 Endocrinopathic Laminitis Frank N
Vasopressin
Velagliflozin
de Laat Ma, Sillence MN
A review of recent developments in the pharmagological prevention and treatment of endocrinopathic laminitis
Animal Production Science published online 16 June 2020. doi.org/10.1071/AN19491
Meier A, Reiche D, de Laat M, Pollitt C, Walsh D, Sillence M
The sodium-glucose co-transporter 2 inhibitor velagliflozin reduces hyperinsulinemia and prevents laminitis in insulin-dysregulated ponies
PLoS ONE 13(9): e0203655 published 13 Sept 2018. https://doi.org/10.1371/journal.pone.0203655
See also: Drug shows promises in preventing laminitis in at-risk ponies - www.horsetalk.co.nz 24 Sept 2018
Giddy up: help for plump ponies is fast on its way - Dec 2018 Queensland University of Technology
de Laat Ma, Sillence MN
A review of recent developments in the pharmagological prevention and treatment of endocrinopathic laminitis
Animal Production Science published online 16 June 2020. doi.org/10.1071/AN19491
Meier A, Reiche D, de Laat M, Pollitt C, Walsh D, Sillence M
The sodium-glucose co-transporter 2 inhibitor velagliflozin reduces hyperinsulinemia and prevents laminitis in insulin-dysregulated ponies
PLoS ONE 13(9): e0203655 published 13 Sept 2018. https://doi.org/10.1371/journal.pone.0203655
See also: Drug shows promises in preventing laminitis in at-risk ponies - www.horsetalk.co.nz 24 Sept 2018
Giddy up: help for plump ponies is fast on its way - Dec 2018 Queensland University of Technology
Venogram
Venograms are used to assess vascular damage in the foot, and can be a valuable tool in the diagnosis and treatment of laminitis, in addition to standard x-rays. Contrast medium is injected into the foot and radiographs taken immediately. A reduction or absence of contrast medium may indicate venous compromise or occlusion, e.g. due to compression. Venograms can be used to evaluate the severity and location of damage and to monitor therapy.
However, venograms are notoriously difficult to carry out accurately and often have artifacts. In Digital Venography in Horses and Its Clinical Application in Europe, D'Arpe and Bernardini, Vet Clin Equine 26 (2010) 339-359, it is stated that "perivascular infiltration of contrast medium is the most frequent artifact found in the venographic technique" - when this occurs, a large pool of contrast medium is seen at the needle insertion site. The authors continue "A characteristic narrowing of the blood vessels and lack of perfusion in the heels indicate that volume is inadequate".
This video on the Equine Digital Venogram by Amy Rucker and Roger Shaw gives examples of venograms on normal and laminitic feet, and examples of inadequate fill v pathology. The video states that with inadequate fill, the vessels are seen to taper, with pathology there is a blunt void.
Video: Equine Digital Venogram by Amy Rucker and Roger Shaw, for the Animal Health Fund
Wylie CE, Pollitt CC
In Horses With Chronic Laminitis, Do Venograms Compared to Plain Radiographs Give Greater Diagnostic or Prognostic Information? A Knowledge Summary.
Veterinary Evidence Online published August 2017
There is no conclusive evidence available to guide recommendations as to whether venograms provide any greater diagnostic or prognostic information compared to the use of plain radiographs in horses with chronic laminitis.
Eastman S, Redden RF, Williams CA
Venograms for Use in Laminitis Treatment
Journal of Equine Veterinary Science Volume 32, Issue 11 , Pages 757-759, November 2012
(F, P, Deepdyve)
D'Arpe L, Bernardini D
Digital venography in horses and its clinical application in Europe
Vet Clin North Am Equine Pract. 2010 Aug;26(2):339-59. doi: 10.1016/j.cveq.2010.06.006 (full)
Rucker A
Clinical Applications of Digital Venography
Journal of Equine Veterinary Science Vol 30 (9) - Sep 1, 2010
(F, Deepdyve)
AAEP Proceedings 2006 Vol 52
How to Perform the Digital Venogram
Rucker A, Redden RF, Arthur EG, Reed SK, Hill BW, Dziuban EM, Renfro DC
The Tipping Point: How Venograms Make the Difference Between Success and Failure When Treating Laminitis - RF (Ric) Redden
Venogram technique, indication and interpretation - R F (Ric) Redden Nov 2005
Equine Pract. 2010 Apr;26(1):135-40
Progression of venographic changes after experimentally induced laminitis
Baldwin GI, Pollitt CC
Vet Clin North Am Equine Pract. 2010 Apr;26(1):167-77
Equine venography and its clinical application in North America
Rucker A
Journal of Equine Veterinary Science Article In Press Sept 2011
Initial Experience Using Contrast Magnetic Resonance Imaging in Laminitic Horses: 18 Studies
Griffin RL, McKnight AL, Rucker A, Bennett SD, Fiser DM
Venography of Chronic Laminitis p 11 of After The Crash - Lessons From Chronic Laminitis
Professor Christopher C Pollitt
Article available at www.Safergrass.org
Western Veterinary Conference 2013
Laminitis rehabilitation: if the corium is happy, there is hope
Debra R. Taylor
Interpreting Venograms and Artifacts - Amy Rucker www.thehorse.com Apr 2003
Understanding the Venogram by Christy M. West - www.thehorse.com - March 2003
In Horses With Chronic Laminitis, Do Venograms Compared to Plain Radiographs Give Greater Diagnostic or Prognostic Information? A Knowledge Summary.
Veterinary Evidence Online published August 2017
There is no conclusive evidence available to guide recommendations as to whether venograms provide any greater diagnostic or prognostic information compared to the use of plain radiographs in horses with chronic laminitis.
Eastman S, Redden RF, Williams CA
Venograms for Use in Laminitis Treatment
Journal of Equine Veterinary Science Volume 32, Issue 11 , Pages 757-759, November 2012
(F, P, Deepdyve)
D'Arpe L, Bernardini D
Digital venography in horses and its clinical application in Europe
Vet Clin North Am Equine Pract. 2010 Aug;26(2):339-59. doi: 10.1016/j.cveq.2010.06.006 (full)
Rucker A
Clinical Applications of Digital Venography
Journal of Equine Veterinary Science Vol 30 (9) - Sep 1, 2010
(F, Deepdyve)
AAEP Proceedings 2006 Vol 52
How to Perform the Digital Venogram
Rucker A, Redden RF, Arthur EG, Reed SK, Hill BW, Dziuban EM, Renfro DC
The Tipping Point: How Venograms Make the Difference Between Success and Failure When Treating Laminitis - RF (Ric) Redden
Venogram technique, indication and interpretation - R F (Ric) Redden Nov 2005
Equine Pract. 2010 Apr;26(1):135-40
Progression of venographic changes after experimentally induced laminitis
Baldwin GI, Pollitt CC
Vet Clin North Am Equine Pract. 2010 Apr;26(1):167-77
Equine venography and its clinical application in North America
Rucker A
Journal of Equine Veterinary Science Article In Press Sept 2011
Initial Experience Using Contrast Magnetic Resonance Imaging in Laminitic Horses: 18 Studies
Griffin RL, McKnight AL, Rucker A, Bennett SD, Fiser DM
Venography of Chronic Laminitis p 11 of After The Crash - Lessons From Chronic Laminitis
Professor Christopher C Pollitt
Article available at www.Safergrass.org
Western Veterinary Conference 2013
Laminitis rehabilitation: if the corium is happy, there is hope
Debra R. Taylor
Interpreting Venograms and Artifacts - Amy Rucker www.thehorse.com Apr 2003
Understanding the Venogram by Christy M. West - www.thehorse.com - March 2003
Vets
RCVS Code of Professional Conduct for Veterinary Surgeons - supporting guidance
A frequently asked question is whether owners should receive copies of x-rays and blood test results. Section 13.5 states that "Where a client has been specifically charged and has paid for radiographic images or other reports, they are legally entitled to them. A practice may choose to make it clear to clients that they are not charged for radiographs or laboratory reports, but for diagnosis or advice only." Section 13.6 explains that under The Data Protection Act 1998, vets must provide copies of any relevant clinical and client records to their clients on payment of an administration fee, including x-rays. The RCVS covers vets in the UK.
Updated June 2017:
"13.11 Under RCVS guidelines, at the request of a client, veterinary surgeons and veterinary nurses must provide copies of any relevant clinical and client records. This includes relevant records which have come from other practices, if they relate to the same animal and the same client
13.12 In many cases it will be made clear to clients that they are not being charged for radiographs or laboratory reports, but for diagnosis or advice only. In situations where images are held on film, the film remains the property of the practice, with the client being charged for diagnosis or advice. In this situation, copies should still be provided in response to a request, wherever possible. Where images are held digitally, clients are also entitled to a copy."
Given the above, it might be sensible when booking an appointment for an owner to make it clear that they want to have and pay for a copy of radiographs and laboratory test results.
The RCVS published a statement on the veterinary use of complementary and alternative medicines in November 2017, which concludes:
“Homeopathy exists without a recognised body of evidence for its use. Furthermore, it is not based on sound scientific principles. In order to protect animal welfare, we regard such treatments as being complementary rather than alternative to treatments for which there is a recognised evidence base or which are based in sound scientific principles. It is vital to protect the welfare of animals committed to the care of the veterinary profession and the public’s confidence in the profession that any treatments not underpinned by a recognised evidence base or sound scientific principles do not delay or replace those that do.”
A frequently asked question is whether owners should receive copies of x-rays and blood test results. Section 13.5 states that "Where a client has been specifically charged and has paid for radiographic images or other reports, they are legally entitled to them. A practice may choose to make it clear to clients that they are not charged for radiographs or laboratory reports, but for diagnosis or advice only." Section 13.6 explains that under The Data Protection Act 1998, vets must provide copies of any relevant clinical and client records to their clients on payment of an administration fee, including x-rays. The RCVS covers vets in the UK.
Updated June 2017:
"13.11 Under RCVS guidelines, at the request of a client, veterinary surgeons and veterinary nurses must provide copies of any relevant clinical and client records. This includes relevant records which have come from other practices, if they relate to the same animal and the same client
13.12 In many cases it will be made clear to clients that they are not being charged for radiographs or laboratory reports, but for diagnosis or advice only. In situations where images are held on film, the film remains the property of the practice, with the client being charged for diagnosis or advice. In this situation, copies should still be provided in response to a request, wherever possible. Where images are held digitally, clients are also entitled to a copy."
Given the above, it might be sensible when booking an appointment for an owner to make it clear that they want to have and pay for a copy of radiographs and laboratory test results.
The RCVS published a statement on the veterinary use of complementary and alternative medicines in November 2017, which concludes:
“Homeopathy exists without a recognised body of evidence for its use. Furthermore, it is not based on sound scientific principles. In order to protect animal welfare, we regard such treatments as being complementary rather than alternative to treatments for which there is a recognised evidence base or which are based in sound scientific principles. It is vital to protect the welfare of animals committed to the care of the veterinary profession and the public’s confidence in the profession that any treatments not underpinned by a recognised evidence base or sound scientific principles do not delay or replace those that do.”
Vitex agnus castus (Chasteberry)
Vitex or Chasteberry is the berry of the Chaste tree. Vitex contains several active components:
Beatrix Roemheld-Hamm
Chasteberry
Am Fam Physician. 2005 Sep 1;72(5):821-824
This hormonal effect appears to be dose-dependent: low doses of extract have resulted in decreased estrogen levels and increased progesterone and prolactin levels, possibly caused by an inhibition of the release of follicle-stimulating hormone (FSH) and stimulation of luteinizing hormone (LH) levels.4,7,12 However, in some studies of persons receiving higher doses, FSH and LH levels remained unchanged,4,10,12 while prolactin release was decreased.4,12 These effects may explain why lower doses of the herb might stimulate breast milk production, whereas higher doses seem to have the opposite effect.
Can Vitex help horses with PPID?
In their chapter on PPID in Equine Laminitis edited by James Belknap 2017, Dianne McFarlane, Philip Johnson and Harold Shott II suggest that the many neutraceuticals and natural remedies marketed for the treatment of PPID are contraindicated for horses with PPID due to their lack of efficacy and safety studies and lack of product regulation and standardization. Discussing the use of Vitex agnus castus, although Sliutz et al. 1993 showed a decrease in prolactin release in rats given Vitex, Jill Beech's 2002 study on 14 horses showed no improvement in clinical signs or blood results. The condition of several of the horses deteriorated while being given Vitex, but 8/9 of the horses improved when then treated with pergolide. The authors conclude that the results of Beech's study "support the use of peroglide rather than chasteberry extract in the treatment of horses with PPID."
Note that products that claim to prevent or treat a disease are illegal in the UK if they do not have a marketing authorisation number - see Report illegal animal medicines.
There are anecdotal reports that horses with PPID may show lifting of depression and improvements in coat shedding when given Vitex, but there is currently no suggestion in unbiased published research that Vitex reduces ACTH concentrations or laminitis risk. When asked whether chasteberry (Vitex) can help a horse with PPID during TheHorse.com's Ask the Vet LIVE event on equine Cushing's disease (PPID) in September 2012, Nicholas Frank replied that the Pennsylvania University study found that Vitex was not effective (see Beech 2002 below). He said there are anecdotal reports of improvements in horses given chasteberry, it may help some horses and not others, but it’s not a substitute for pergolide, which is clearly effective in controlling PPID (full notes of the webinar).
Beech J, Donaldson MT, Lindborg S
Comparison of Vitex agnus castus Extract and Pergolide in Treatment of Equine Cushing’s Syndrome
AAEP proceedings Vol 48 2002
"Our study showed that Vitex agnus castus Extract, the commercially available form of Vitex agnus castus, did not have a beneficial effect in horses with pituitary pars intermedia hyperplasia (Equine Cushing’s Syndrome); clinical signs sometimes worsened, plasma ACTH concentrations decreased in only 1 of 12 horses, and the dexamethasone suppression test remained abnormal in the horses tested. In contrast, with the exception of one horse, pergolide had a beneficial effect, although individual horses often required dosages above what many practitioners customarily use. Whether higher doses of Vitex agnus castus would have an effect is speculative..... Until there is more information, the authors do not advise using Vitex agnus castus for treating Equine Cushing's Syndrome."
Bradaric Z, May A, Gehlen H
Use of the chasteberry preparation Corticosal® for the treatment of pituitary pars intermedia dysfunction in horses
Pferdeheilkunde 29 (2013) 6 (November/Dezember) 721-728
Could Vitex be detrimental to horses with PPID?
There is evidence in other species that a low dose of Vitex could inhibit dopamine, which is the opposite of the effect wanted for horses with PPID.
Wikipedia: Vitex agnus castus is assumed to have dopaminergic effects resulting in changes in prolactin secretion. At low doses Vitex agnus castus inhibits activation of dopamine 2 receptors by competitive binding, causing a slight increase in release of prolactin. At higher concentrations the binding activity is sufficient to reduce the release of prolactin.
Beatrix Roemheld-Hamm
Chasteberry
Am Fam Physician. 2005 Sep 1;72(5):821-824
Lower doses of Vitex may stimulate breast milk production (i.e. inhibit dopamine), whereas higher doses may reduce breast milk production.
The effects of a special Agnus castus extract (BP1095E1) on prolactin secretion in healthy male subjects
Merz PG et al. Exp Clin Endocrinol Diabetes. 1996;104(6):447-53 (PubMed)
"In contrast to the administration of placebo, the 1-hour AUC after TRH stimulation resulted in a significant increase with the lowest dose and a significant reduction with the highest dose. The results suggest effects of the special Agnus castus extract which are dependent on the dose administered and the initial level of prolactin concentration."
Note that some feeds aimed at horses with PPID (Cushing's) contain Vitex agnus castus/Chasteberry, often in low doses. These feeds may not be suitable for horses with PPID!
Can Vitex be used at the same time as pergolide?
Human medicine contains warnings that Vitex should not be used at the same time as pergolide (Prascend) or other dopamine agonists:
This paper from 2008 suggests that Vitex shouldn't be used at the same time as dopamine agonists and drugs used to treat Parkinson's disease in humans:
Safety and Efficacy of Chastetree (Vitex Agnus-Castus) during Pregnancy and Lactation
Jean-Jacques Dugoua et al.
Can J Clin Pharmacol Vol 15 (1) Winter 2008:e74-e79; January 18, 2008 (full paper)
Chasteberry - Memorial Sloan Kettering Cancer Centre
Herb-Drug interactions: Dopamine agonists: "Chasteberry may interfere with the action of these drugs or enhance their side effects".
"..because V. agnus-castus inhibits the secretion of prolactin via a dopamine-agonist action, drug interactions may occur with the D2 family of dopamine-receptor agonists (bromocriptine, pergolide, pramipexole, ropinirole, cabergoline." - p 222 Herbal Toxicology - Amita Sarkar 2009
"Because chasteberry may affect the dopamine system in the brain, people taking dopamine-related medications, such as certain antipsychotic drugs and Parkinson's disease medications, should avoid using chasteberry." - NCCIH
However anecdotally owners have used both pergolide and Vitex. It would seem sensible to discuss the use of Vitex alongside or instead of pergolide with your vet before making any changes to your horse's treatment, and to carefully monitor clinical symptoms and blood results (ACTH, insulin).
How does Vitex work?
Vitex has dopaminergic effects, i.e. it acts like dopamine in the body, and it has been shown to reduce prolactin, a hormone secreted from the pars distalis of the pituitary gland, which is inhibited by dopamine in a similar way to the hormones produced by the pars intermedia. It may also have opioid-like activity.
See Examine.com Vitex Agnus Castus or WHO monographs on selected medicinal plants Volume 4 for a full description of its properties with scientific references.
Agnus castus extracts inhibit prolactin secretion of rat pituitary cells
Sliutz G et al., Horm Metab Res. 1993 May;25(5):253-5
"Both extracts from Vitex agnus castus as well as synthetic dopamine agonists (Lisuride) significantly inhibit basal as well as TRH-stimulated prolactin secretion of rat pituitary cells in vitro and as a consequence inhibition of prolactin secretion could be blocked by adding a dopamine receptor blocker. Therefore because of its dopaminergic effect Agnus castus could be considered as an efficient alternative phytotherapeutic drug in the treatment of slight hyperprolactinaemia."
Chaste tree (Vitex agnus-castus) - pharmacology and clinical indications
Wuttke W et al., Phytomedicine 2003 May;10(4):348-57
"Serum prolactin levels were indeed reduced in the patients treated with the extract (of Vitex agnus castus). The search for the prolactin-suppressive principle(s) yielded a number of compounds with dopaminergic properties: they bound to recombinant DA2-receptor protein and suppressed prolactin release from cultivated lactotrophs as well as in animal experiments."
What dose of Vitex should be used?
As described above, there is evidence in other species that a low dose of Vitex could inhibit dopamine, which is the opposite of the effect wanted for horses with PPID.
If given at all, the manufacturer's recommended dose should generally be given.
Results of a field trial on Vitex agnus castus (Hormonise) published in Horse Journal Dec 2000 suggested that the effective dosage was 10 cc/90 kg body weight. Some anecdotal reports suggest a minimum dose of around 30 g/day (for a 500 kg horse) may be needed to see positive effects (see message 177723 ECIR group).
What form of Vitex should be used?
Ethanol or hexane extracts may be required for dopaminergic activity:
Pharmacological activities of Vitex agnus-castus extracts in vitroMeier B et al. Phytomedicine. 2000 Oct;7(5):373-81(PubMed)Using ethanol extracts: "Our results indicate a dopaminergic effect of Vitex agnus-castus extracts and suggest additional pharmacological actions via opioid receptors".
Are there any side effects associated with Vitex?
Side effects in horses don't appear to be commonly reported, but a recent paper suggested that high doses of Vitex may cause anxiety in rats:
Possible Modulation of the Anexiogenic Effects of Vitex Agnus-castus by the Serotonergic System
Yaghmaei et al. Iran J Basic Med Sci. 2012 Mar-Apr; 15(2): 768–776
25 November 2010 EMA/HMPC/144003/2009 Committee on Herbal Medicinal Products (HMPC)
Assessment report on Vitex agnus-castus L., fructus
This report by the European Medicines Agency lists various side effects, and also mentions possible liver toxicity (p 14).
From p 33: "In Germany, tumours of the pituitary gland are labelled as an absolute contraindication. Because of the probable prolactin decreasing effect of Vitex agnus-castus, a special warning seems to be the adequate way to inform doctors and patients: “Agnus castus is thought to act on the pituitary-hypothalamic axis and therefore patients with a history of a pituitary disorder should consult with a doctor before using
this product". "Because of the possible dopaminergic" .. "effects of Vitex agnus-castus, interactions with dopamine agonists, dopamine antagonists" .. "cannot be excluded".
Vitex should not be used during pregnancy or lactation.
Research
Bradaric Z, May A, Gehlen H
Use of the chasteberry preparation Corticosal® for the treatment of pituitary pars intermedia dysfunction in horses
Pferdeheilkunde 29 (2013) 6 (November/Dezember) 721-728
Rani A, Sharma A
The genus Vitex: A review
Pharmacogn Rev. 2013 Jul;7(14):188-98. doi: 10.4103/0973-7847.120522. PMID: 24347927; PMCID: PMC3841997
Beatrix Roemheld-Hamm
Chasteberry
Am Fam Physician. 2005 Sep 1;72(5):821-824
Beech et al.
Comparison of Vitex agnus castus Extract and Pergolide in Treatment of Equine Cushing’s Syndrome
AAEP proceedings Vol 48 2002
Beatrix Roemheld-Hamm
Chasteberry
Am Fam Physician. 2005 Sep 1;72(5):821-824
This hormonal effect appears to be dose-dependent: low doses of extract have resulted in decreased estrogen levels and increased progesterone and prolactin levels, possibly caused by an inhibition of the release of follicle-stimulating hormone (FSH) and stimulation of luteinizing hormone (LH) levels.4,7,12 However, in some studies of persons receiving higher doses, FSH and LH levels remained unchanged,4,10,12 while prolactin release was decreased.4,12 These effects may explain why lower doses of the herb might stimulate breast milk production, whereas higher doses seem to have the opposite effect.
Can Vitex help horses with PPID?
In their chapter on PPID in Equine Laminitis edited by James Belknap 2017, Dianne McFarlane, Philip Johnson and Harold Shott II suggest that the many neutraceuticals and natural remedies marketed for the treatment of PPID are contraindicated for horses with PPID due to their lack of efficacy and safety studies and lack of product regulation and standardization. Discussing the use of Vitex agnus castus, although Sliutz et al. 1993 showed a decrease in prolactin release in rats given Vitex, Jill Beech's 2002 study on 14 horses showed no improvement in clinical signs or blood results. The condition of several of the horses deteriorated while being given Vitex, but 8/9 of the horses improved when then treated with pergolide. The authors conclude that the results of Beech's study "support the use of peroglide rather than chasteberry extract in the treatment of horses with PPID."
Note that products that claim to prevent or treat a disease are illegal in the UK if they do not have a marketing authorisation number - see Report illegal animal medicines.
There are anecdotal reports that horses with PPID may show lifting of depression and improvements in coat shedding when given Vitex, but there is currently no suggestion in unbiased published research that Vitex reduces ACTH concentrations or laminitis risk. When asked whether chasteberry (Vitex) can help a horse with PPID during TheHorse.com's Ask the Vet LIVE event on equine Cushing's disease (PPID) in September 2012, Nicholas Frank replied that the Pennsylvania University study found that Vitex was not effective (see Beech 2002 below). He said there are anecdotal reports of improvements in horses given chasteberry, it may help some horses and not others, but it’s not a substitute for pergolide, which is clearly effective in controlling PPID (full notes of the webinar).
Beech J, Donaldson MT, Lindborg S
Comparison of Vitex agnus castus Extract and Pergolide in Treatment of Equine Cushing’s Syndrome
AAEP proceedings Vol 48 2002
"Our study showed that Vitex agnus castus Extract, the commercially available form of Vitex agnus castus, did not have a beneficial effect in horses with pituitary pars intermedia hyperplasia (Equine Cushing’s Syndrome); clinical signs sometimes worsened, plasma ACTH concentrations decreased in only 1 of 12 horses, and the dexamethasone suppression test remained abnormal in the horses tested. In contrast, with the exception of one horse, pergolide had a beneficial effect, although individual horses often required dosages above what many practitioners customarily use. Whether higher doses of Vitex agnus castus would have an effect is speculative..... Until there is more information, the authors do not advise using Vitex agnus castus for treating Equine Cushing's Syndrome."
Bradaric Z, May A, Gehlen H
Use of the chasteberry preparation Corticosal® for the treatment of pituitary pars intermedia dysfunction in horses
Pferdeheilkunde 29 (2013) 6 (November/Dezember) 721-728
Could Vitex be detrimental to horses with PPID?
There is evidence in other species that a low dose of Vitex could inhibit dopamine, which is the opposite of the effect wanted for horses with PPID.
Wikipedia: Vitex agnus castus is assumed to have dopaminergic effects resulting in changes in prolactin secretion. At low doses Vitex agnus castus inhibits activation of dopamine 2 receptors by competitive binding, causing a slight increase in release of prolactin. At higher concentrations the binding activity is sufficient to reduce the release of prolactin.
Beatrix Roemheld-Hamm
Chasteberry
Am Fam Physician. 2005 Sep 1;72(5):821-824
Lower doses of Vitex may stimulate breast milk production (i.e. inhibit dopamine), whereas higher doses may reduce breast milk production.
The effects of a special Agnus castus extract (BP1095E1) on prolactin secretion in healthy male subjects
Merz PG et al. Exp Clin Endocrinol Diabetes. 1996;104(6):447-53 (PubMed)
"In contrast to the administration of placebo, the 1-hour AUC after TRH stimulation resulted in a significant increase with the lowest dose and a significant reduction with the highest dose. The results suggest effects of the special Agnus castus extract which are dependent on the dose administered and the initial level of prolactin concentration."
Note that some feeds aimed at horses with PPID (Cushing's) contain Vitex agnus castus/Chasteberry, often in low doses. These feeds may not be suitable for horses with PPID!
Can Vitex be used at the same time as pergolide?
Human medicine contains warnings that Vitex should not be used at the same time as pergolide (Prascend) or other dopamine agonists:
This paper from 2008 suggests that Vitex shouldn't be used at the same time as dopamine agonists and drugs used to treat Parkinson's disease in humans:
Safety and Efficacy of Chastetree (Vitex Agnus-Castus) during Pregnancy and Lactation
Jean-Jacques Dugoua et al.
Can J Clin Pharmacol Vol 15 (1) Winter 2008:e74-e79; January 18, 2008 (full paper)
Chasteberry - Memorial Sloan Kettering Cancer Centre
Herb-Drug interactions: Dopamine agonists: "Chasteberry may interfere with the action of these drugs or enhance their side effects".
"..because V. agnus-castus inhibits the secretion of prolactin via a dopamine-agonist action, drug interactions may occur with the D2 family of dopamine-receptor agonists (bromocriptine, pergolide, pramipexole, ropinirole, cabergoline." - p 222 Herbal Toxicology - Amita Sarkar 2009
"Because chasteberry may affect the dopamine system in the brain, people taking dopamine-related medications, such as certain antipsychotic drugs and Parkinson's disease medications, should avoid using chasteberry." - NCCIH
However anecdotally owners have used both pergolide and Vitex. It would seem sensible to discuss the use of Vitex alongside or instead of pergolide with your vet before making any changes to your horse's treatment, and to carefully monitor clinical symptoms and blood results (ACTH, insulin).
How does Vitex work?
Vitex has dopaminergic effects, i.e. it acts like dopamine in the body, and it has been shown to reduce prolactin, a hormone secreted from the pars distalis of the pituitary gland, which is inhibited by dopamine in a similar way to the hormones produced by the pars intermedia. It may also have opioid-like activity.
See Examine.com Vitex Agnus Castus or WHO monographs on selected medicinal plants Volume 4 for a full description of its properties with scientific references.
Agnus castus extracts inhibit prolactin secretion of rat pituitary cells
Sliutz G et al., Horm Metab Res. 1993 May;25(5):253-5
"Both extracts from Vitex agnus castus as well as synthetic dopamine agonists (Lisuride) significantly inhibit basal as well as TRH-stimulated prolactin secretion of rat pituitary cells in vitro and as a consequence inhibition of prolactin secretion could be blocked by adding a dopamine receptor blocker. Therefore because of its dopaminergic effect Agnus castus could be considered as an efficient alternative phytotherapeutic drug in the treatment of slight hyperprolactinaemia."
Chaste tree (Vitex agnus-castus) - pharmacology and clinical indications
Wuttke W et al., Phytomedicine 2003 May;10(4):348-57
"Serum prolactin levels were indeed reduced in the patients treated with the extract (of Vitex agnus castus). The search for the prolactin-suppressive principle(s) yielded a number of compounds with dopaminergic properties: they bound to recombinant DA2-receptor protein and suppressed prolactin release from cultivated lactotrophs as well as in animal experiments."
What dose of Vitex should be used?
As described above, there is evidence in other species that a low dose of Vitex could inhibit dopamine, which is the opposite of the effect wanted for horses with PPID.
If given at all, the manufacturer's recommended dose should generally be given.
Results of a field trial on Vitex agnus castus (Hormonise) published in Horse Journal Dec 2000 suggested that the effective dosage was 10 cc/90 kg body weight. Some anecdotal reports suggest a minimum dose of around 30 g/day (for a 500 kg horse) may be needed to see positive effects (see message 177723 ECIR group).
What form of Vitex should be used?
Ethanol or hexane extracts may be required for dopaminergic activity:
Pharmacological activities of Vitex agnus-castus extracts in vitroMeier B et al. Phytomedicine. 2000 Oct;7(5):373-81(PubMed)Using ethanol extracts: "Our results indicate a dopaminergic effect of Vitex agnus-castus extracts and suggest additional pharmacological actions via opioid receptors".
Are there any side effects associated with Vitex?
Side effects in horses don't appear to be commonly reported, but a recent paper suggested that high doses of Vitex may cause anxiety in rats:
Possible Modulation of the Anexiogenic Effects of Vitex Agnus-castus by the Serotonergic System
Yaghmaei et al. Iran J Basic Med Sci. 2012 Mar-Apr; 15(2): 768–776
25 November 2010 EMA/HMPC/144003/2009 Committee on Herbal Medicinal Products (HMPC)
Assessment report on Vitex agnus-castus L., fructus
This report by the European Medicines Agency lists various side effects, and also mentions possible liver toxicity (p 14).
From p 33: "In Germany, tumours of the pituitary gland are labelled as an absolute contraindication. Because of the probable prolactin decreasing effect of Vitex agnus-castus, a special warning seems to be the adequate way to inform doctors and patients: “Agnus castus is thought to act on the pituitary-hypothalamic axis and therefore patients with a history of a pituitary disorder should consult with a doctor before using
this product". "Because of the possible dopaminergic" .. "effects of Vitex agnus-castus, interactions with dopamine agonists, dopamine antagonists" .. "cannot be excluded".
Vitex should not be used during pregnancy or lactation.
Research
Bradaric Z, May A, Gehlen H
Use of the chasteberry preparation Corticosal® for the treatment of pituitary pars intermedia dysfunction in horses
Pferdeheilkunde 29 (2013) 6 (November/Dezember) 721-728
Rani A, Sharma A
The genus Vitex: A review
Pharmacogn Rev. 2013 Jul;7(14):188-98. doi: 10.4103/0973-7847.120522. PMID: 24347927; PMCID: PMC3841997
Beatrix Roemheld-Hamm
Chasteberry
Am Fam Physician. 2005 Sep 1;72(5):821-824
Beech et al.
Comparison of Vitex agnus castus Extract and Pergolide in Treatment of Equine Cushing’s Syndrome
AAEP proceedings Vol 48 2002
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Weight
Measuring and monitoring a horse's weight is important for picking up weight loss or gain, for devising a suitable diet, for accurately dosing worming and medical treatments, and for calculating how much rider weight a horse should carry. Ideally weigh and body condition score your horse every 2 weeks. See Body Condition Scoring Weight is most accurately measured with a weighbridge or scale, and some veterinary practices and feed companies have mobile weighbridges that can be brought to your yard. Otherwise you can use a weigh tape or estimate weight using measurements and calculations. A weighbridge should be placed on a hard flat surface and calibrated to a known weight. Tape measurements should be carried out with the horse standing on level ground and standing square with the head up in a natural position. Girth measurements should be taken when the horse breathes out. The Carroll and Huntingdon (1988) formula of (girth squared × length) /11,877 (measurements must be in centimetres) is considered to be the most accurate estimate of bodyweight, and suitable for adult ponies and horses (not pregnant mares). |
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A weigh tape should be specifically for horses or ponies - the Dodson & Horrell weigh tape measures horses on one side and ponies on the other, and research by Ellis & Hollands published in 2002 found that compared to a weigh bridge, the D&H tape had 100.5% (ponies) and 98.6% (horses) accuracy, compared to 90.8% to 112.0% accuracy of 2 other tapes that didn't differentiate by height. Follow the instructions that come with a weight tape!
This article has a useful horse weight calculator using the girth and length measurements, and explains exactly how to take the correct measurements:
Horse Weight Calculator - Mariette Van Den Berg, horsesandpeople.com.au, May 2020
Research:
Jensen RB, Rockhold LL, Tauson AH
Weight estimation and hormone concentrations related to body condition in Icelandic and Warmblood horses: a field study
Acta Vet Scand. 2019;61(1):63. Published 2019 Dec 26. doi:10.1186/s13028-019-0498-5
43 Icelandic and 38 Warmblood horses were weighed using a weighbridge and measured. The Carroll and Huntingdon (1988) formula of (girth squared × length) /11,877 (measurements in cm) was found to be the most accurate weight estimate formula when compared to weighbridge weights. Body condition scores were assessed using both the 0-5 point Carroll and Huntingdon (1988) and 9 point Henneke (1983) scales, and found to be strongly correlated.
Assessment of body condition and bodyweight - Rebecca Carter & Alexandra Dugdale, veteriankey.com 2016
Ellis JM, Hollands T
Use of height-specific weigh tapes to estimate the bodyweight of horses
Vet Rec. 18 May 2002;150(20):632-4. doi: 10.1136/vr.150.20.632. PMID: 12046788
Weight gain
Effects of weight gain
Delarocque J, Frers F, Huber K, Jung K, Feige K, Warnken T.
Metabolic impact of weight variations in Icelandic horses.
PeerJ. 2021 Jan 28;9:e10764. doi: 10.7717/peerj.10764. PMID: 33575132; PMCID: PMC7847705.
Keywords: Equine metabolic syndrome; Insulin dysregulation; Metabolomics; Obesity; Oral glucose test; Pathway analysis.
Effects of weight gain
Delarocque J, Frers F, Huber K, Jung K, Feige K, Warnken T.
Metabolic impact of weight variations in Icelandic horses.
PeerJ. 2021 Jan 28;9:e10764. doi: 10.7717/peerj.10764. PMID: 33575132; PMCID: PMC7847705.
Keywords: Equine metabolic syndrome; Insulin dysregulation; Metabolomics; Obesity; Oral glucose test; Pathway analysis.
Weight loss
For weight loss, energy in must be less than energy out.
Either the total amount of energy in feed must be reduced, or exercise (energy used) increased, or both. However, if the horse has laminitis and cannot exercise, the total amount of energy in feed must be reduced.
This will generally mean reducing the quantity of feed, but most horses like eating, and underfeeding may lead to health and behavioural problems. The ideal weight loss diet will not reduce the quantity fed significantly, but will reduce the amount of energy contained in the feed.
The NRC Nutrient Requirements of Horses 2007 has set a minimum maintenance requirement for digestible energy (DE) of 30.3 kcal/kg bodyweight (BW), and an average maintenance requirement of 33.3 kcal/kg BW (this may not apply to every type of horse, and particularly may be too high for draft horses). Therefore for weight loss, the DE (energy fed) should be less than the maintenance amount.
Dugdale AH, Curtis GC, Cripps P, Harris PA, Argo CM.
Effect of dietary restriction on body condition, composition and welfare of overweight and obese pony mares.
Equine Vet J. 2010 Oct;42(7):600-10.
Overweight/obese pony mares were fed 1% of their body weight of a chaff-based complete diet (DE 8.5 MJ/kg DM) as dry matter for 12 weeks.
In this research, a pony with an initial body weight of 250 kg would have been fed 1% (dry weight) of its body weight, so 2.5 kg. The DE of the chaff-based feed was 8.5 MJ/kg DM. 8.5 MJ/kg / 4.184 = 2.03 Mcal/kg. So total daily energy fed = 2.5 kg x 2.03 Mcal/kg = 5.075 Mcal/day. Dividing 5.075 Mcal/day by the pony's weight of 250 kg = 0.0203 Mcal/kg BW, or 20.3 kcal/kg BW - 67% of the NRC's minimum maintenance DE requirement.
If you found a hay with a DE of say 1.58 Mcal/kg (6.6 MJ/kg), you would be able to feed 3.2 kg (DM) and provide the same amount of energy - that's 28% more dry matter intake, and over 1.25% of the pony's body weight.
Research
Morrison PK, Newbold CJ, Jones E, Worgan HJ, Grove-White DH, Dugdale AH, Barfoot C, Harris PA, Argo CM.
The equine gastrointestinal microbiome: impacts of weight-loss.
BMC Vet Res. 2020 Mar 4;16(1):78. doi: 10.1186/s12917-020-02295-6. PMID: 32131835; PMCID: PMC7057583.
Moore JL, Siciliano PD, Pratt-Phillips SE.
Effects of Diet Versus Exercise on Morphometric Measurements, Blood Hormone Concentrations, and Oral Sugar Test Response in Obese Horses.
J Equine Vet Sci. 2019 Jul;78:38-45. doi: 10.1016/j.jevs.2019.03.214. Epub 2019 Apr 4. PMID: 31203982.
Keywords: Exercise; Horses; Insulin; Weight loss.
5 obese horses were put on a diet of 85% of DE requirements, and 5 obese horses were given exercise to expend 15% of DE requirements, for 4 weeks. Both groups had similar decreases in body weight, body measurements, body condition score and cresty neck score, but the exercised horses had significantly greater neck circumference losses , and improvements in insulin:glucose ratio, insulin sensitivity and leptin.
Bamford NJ, Potter SJ, Baskerville CL, Harris PA, Bailey SR
Influence of dietary restriction and low-intensity exercise on weight loss and insulin sensitivity in obese equids
Journal of Veterinary Internal Medicine December 2018 33(1) DOI: 10.1111/jvim.153
Effects of Dietary Restriction in Horses - Kentucky Equine Research Staff - 21 March 2013
WHW - Right weight advice - videos and leaflets on recognising obesity and managing a horse's weight
Gill JC, Pratt-Phillips SE, Mansmann R, Siciliano PD
Weight Loss Management in Client-Owned Horses
Journal of Equine Veterinary Science Volume 39, April 2016, Pages 80-89 (DeepDyve)
Argo CM, Dugdale AH, McGowan CM
Considerations for the use of restricted, soaked grass hay diets to promote weight loss in the management of equine metabolic syndrome and obesity
The Veterinary Journal Volume 206, Issue 2, November 2015, Pages 170-177
McGowan CM, Dugdale AH, Pinchbeck GL, Argo CM
Dietary restriction in combination with a nutraceutical supplement for the management of equine metabolic syndrome in horses
Vet J. 2013 May;196(2):153-9 Epub 2012 Nov 8 (DeepDyve)
Gordon ME, Jerina ML, Raub RH, Davison KA, Young JK, Williamson KK
The effects of dietary manipulation and exercise on weight loss and related indices of health in horses
Comparative Exercise Physiology 6(1); 33–42 2009
Either the total amount of energy in feed must be reduced, or exercise (energy used) increased, or both. However, if the horse has laminitis and cannot exercise, the total amount of energy in feed must be reduced.
This will generally mean reducing the quantity of feed, but most horses like eating, and underfeeding may lead to health and behavioural problems. The ideal weight loss diet will not reduce the quantity fed significantly, but will reduce the amount of energy contained in the feed.
The NRC Nutrient Requirements of Horses 2007 has set a minimum maintenance requirement for digestible energy (DE) of 30.3 kcal/kg bodyweight (BW), and an average maintenance requirement of 33.3 kcal/kg BW (this may not apply to every type of horse, and particularly may be too high for draft horses). Therefore for weight loss, the DE (energy fed) should be less than the maintenance amount.
Dugdale AH, Curtis GC, Cripps P, Harris PA, Argo CM.
Effect of dietary restriction on body condition, composition and welfare of overweight and obese pony mares.
Equine Vet J. 2010 Oct;42(7):600-10.
Overweight/obese pony mares were fed 1% of their body weight of a chaff-based complete diet (DE 8.5 MJ/kg DM) as dry matter for 12 weeks.
In this research, a pony with an initial body weight of 250 kg would have been fed 1% (dry weight) of its body weight, so 2.5 kg. The DE of the chaff-based feed was 8.5 MJ/kg DM. 8.5 MJ/kg / 4.184 = 2.03 Mcal/kg. So total daily energy fed = 2.5 kg x 2.03 Mcal/kg = 5.075 Mcal/day. Dividing 5.075 Mcal/day by the pony's weight of 250 kg = 0.0203 Mcal/kg BW, or 20.3 kcal/kg BW - 67% of the NRC's minimum maintenance DE requirement.
If you found a hay with a DE of say 1.58 Mcal/kg (6.6 MJ/kg), you would be able to feed 3.2 kg (DM) and provide the same amount of energy - that's 28% more dry matter intake, and over 1.25% of the pony's body weight.
Research
Morrison PK, Newbold CJ, Jones E, Worgan HJ, Grove-White DH, Dugdale AH, Barfoot C, Harris PA, Argo CM.
The equine gastrointestinal microbiome: impacts of weight-loss.
BMC Vet Res. 2020 Mar 4;16(1):78. doi: 10.1186/s12917-020-02295-6. PMID: 32131835; PMCID: PMC7057583.
Moore JL, Siciliano PD, Pratt-Phillips SE.
Effects of Diet Versus Exercise on Morphometric Measurements, Blood Hormone Concentrations, and Oral Sugar Test Response in Obese Horses.
J Equine Vet Sci. 2019 Jul;78:38-45. doi: 10.1016/j.jevs.2019.03.214. Epub 2019 Apr 4. PMID: 31203982.
Keywords: Exercise; Horses; Insulin; Weight loss.
5 obese horses were put on a diet of 85% of DE requirements, and 5 obese horses were given exercise to expend 15% of DE requirements, for 4 weeks. Both groups had similar decreases in body weight, body measurements, body condition score and cresty neck score, but the exercised horses had significantly greater neck circumference losses , and improvements in insulin:glucose ratio, insulin sensitivity and leptin.
Bamford NJ, Potter SJ, Baskerville CL, Harris PA, Bailey SR
Influence of dietary restriction and low-intensity exercise on weight loss and insulin sensitivity in obese equids
Journal of Veterinary Internal Medicine December 2018 33(1) DOI: 10.1111/jvim.153
Effects of Dietary Restriction in Horses - Kentucky Equine Research Staff - 21 March 2013
WHW - Right weight advice - videos and leaflets on recognising obesity and managing a horse's weight
Gill JC, Pratt-Phillips SE, Mansmann R, Siciliano PD
Weight Loss Management in Client-Owned Horses
Journal of Equine Veterinary Science Volume 39, April 2016, Pages 80-89 (DeepDyve)
Argo CM, Dugdale AH, McGowan CM
Considerations for the use of restricted, soaked grass hay diets to promote weight loss in the management of equine metabolic syndrome and obesity
The Veterinary Journal Volume 206, Issue 2, November 2015, Pages 170-177
McGowan CM, Dugdale AH, Pinchbeck GL, Argo CM
Dietary restriction in combination with a nutraceutical supplement for the management of equine metabolic syndrome in horses
Vet J. 2013 May;196(2):153-9 Epub 2012 Nov 8 (DeepDyve)
Gordon ME, Jerina ML, Raub RH, Davison KA, Young JK, Williamson KK
The effects of dietary manipulation and exercise on weight loss and related indices of health in horses
Comparative Exercise Physiology 6(1); 33–42 2009
Worms and parasites
General information about worming
AAEP Parasite Control Guidelines 2016
Westgate Laboratories
Intelligent Worming
Diagnosteq
Anthelmintic Resistance and the Responsible Use of Anthelmintics - VMD
PPID and worms/parasites
Horses with PPID have been shown to have higher than normal worm egg counts, and an appropriate worm control programme should form part of the management plan for a PPID horse.
Christen G, Gerber V, van der Kolk JH, Frey CF, Fouché N
Fecal strongyle egg counts in horses with suspected pre-clinical pituitary pars intermedia dysfunction before and after treatment with pergolide
The Veterinary Journal May 2018 Volume 235, Pages 60-62. https://doi.org/10.1016/j.tvjl.2018.03.007 (DeepDyve)
J Am Vet Med Assoc. 2010 Feb 1;236(3):330-4. (PubMed)
Fecal egg counts after anthelmintic administration to aged horses and horses with pituitary pars intermedia dysfunction
McFarlane D, Hale GM, Johnson EM, Maxwell LK
"For similar environmental conditions, horses with PPID were more likely to have higher fecal egg counts than were healthy horses. Therefore, horses with PPID may need to have a more aggressive parasite prevention program than do healthy horses."
Is praziquantel safe for EMS/PPID horses?
TLS has seen suggestions that praziquantel should not be used for insulin resistant horses, seemingly based on this research:
Arzneimittelforschung. 1996 Apr;46(4):433-5 (PubMed)
Effect of praziquantel on serum glucose and insulin levels in normal and hyperglycemic rats
el-Kashef HA, Salem HA, Said SA, Elmazar MM.
"The effects of praziquantel (CAS 55268-74-1) on serum glucose and insulin levels in normoglycemic and hyperglycemic rats were studied. Also the combined effect of praziquantel and glibenclamide (CAS 10238-21-8) on oral glucose tolerance in rats was investigated. Praziquantel, given orally in a dose of 250 mg/kg, significantly increased serum glucose level in hyperglycemic rats without changing serum insulin level. After oral glucose load, praziquantel produced a significant increase in serum glucose level and antagonized the hypoglycemic action of glibenclamide. These results indicate that praziquantel significantly increased serum glucose level in both hyperglycemic rats and after glucose load. Since insulin levels are not significantly altered by praziquantel, the hyperglycemic effect of this drug may be attributed to inhibition of peripheral glucose utilization. Care should be taken if praziquantel is prescribed to diabetic patients."
The dose of praziquantel used in this research was 250 mg/kg bodyweight (BW) in rats - 100 x the highest dose used in any horse wormer -
Doses of praziquantel in horse wormers:
Equest Pramox 2.5 mg/kg BW
Equimax 1.5 mg/kg BW
Eqvalan Duo 1 mg/kg BW
Equitape 1 mg/kg BW (Equitape is discontinued from sale in the UK from October 2018)
In the research, praziquantel only increased basal serum glucose levels in rats that already had above normal glucose levels - no mention is made of praziquantel increasing glucose levels in the normoglycaemic rats. The serum insulin level was not changed. The serum glucose level was increased when an oral glucose tolerance test was carried out on rats given praziquantel, presumably this was in both hyperglycaemic and normoglycaemic rats. Therefore it might be sensible to avoid carrying out an oral glucose test or giving an exceptionally large amount of glucose to any horse within a few days of using Praziquantel.
Insulin resistant horses do not generally have above normal glucose levels.
We have not found any advice that diabetic/hyperglycaemic humans should avoid or take special care with praziquantel - datasheets for Biltricide (praziquantel for human use) do not appear to mention diabetes or hyperglycaemia.
We have been unable to find any evidence suggesting that praziquantel should be avoided for horses with insulin resistance. As always, if you have any concerns, please discuss with your vet.
Adverse effects of worming
There are anecdotal reports of episodes of laminitis or "footiness" following the use of anthelmintics (de-worming drugs). Post-dosing colic is likely to be attributable to parasite death, and using single-dose/single chemical wormers may be recommended to stagger parasite death:Virabac Animal Health Equine Worming Training Manual p 45:
"Equine Anthelmintic drugs on the whole have very good safety margins and primary adverse reactions are extremely rare, however, post-dosing colic is a recognized phenomenon with most drugs.
When it does occur, colic is usually mild and transient (spasmodic) and resolves without any treatment. It is generally accepted that this is more likely to be attributable to parasite death causing intestinal irritation rather than the drugs themselves and consequently the risk of this problem is greater in horses/ponies carrying heavier burdens."
The following adverse effects/contra-indications are from the NOAH datasheets or VMD SPCs for each wormer:
Wormers containing praziquantel:
Equitape - "In horses with severe infections, treatment may result in mild, transient colic and loose faeces due to the destruction of the tapeworms." (As at 2021 no Equitape is no longer being made, but praziquantel may be available through your vet - see Westgatelabs.co.uk).
Equimax (paste) - "Some horses carrying heavy infection of Onchocerca microfilariae have experienced reactions with swelling and itching after treatment. It is assumed to be the result of death of large numbers of microfilariae."
Equimax tablets - "Colic, diarrhoea and anorexia have been reported in very rare occasions post treatment, in particular when there is heavy worm burden. In very rare occasions, allergic reactions such as hypersalivation, lingual oedema and urticaria, tachycardia, congested mucus membranes, and subcutaneous oedema have been reported following treatment with the product."
Eqvalan Duo - "Some horses with heavy infections of Onchocerca spp. microfilariae have experienced oedema and pruritus following treatment, assumed to be the result of the death of large numbers of microfilariae. These signs resolve within a few days but symptomatic treatment may be advisable. In cases of heavy infestations with tapeworms, signs of mild, transient colic and diarrhoea may be observed. Following administration of EQVALAN DUO, there have been rare reports of inflammation of the mouth, lip and tongue, which results in various clinical signs such as oedema, hypersalivation, erythema, tongue disorder and stomatitis. These reactions have been transitory in nature, appearing within 1 hour and abating within 24 to 48 hours following administration. In case of severe oral reactions symptomatic treatment is recommended."
Equest Pramox - "Mouth pain, flaccid lower lip, swelling of the muzzle, hypersalivation and anorexia have been observed in rare cases. Ataxia has been reported on rare occasions and lethargy in very rare cases. These adverse effects are transient and disappear spontaneously. In case of very high worm burdens, destruction of the parasites may cause a mild transient colic and loose faeces in the treated horse."
Datasheets for other worming chemicals can be found on the NOAH website or Veterinary Medicines Directorate Product Information Database (UK).
Worming programmes for horses that may be at high risk of high worm burdens or that have had laminitis or been diagnosed with EMS or PPID should be discussed with a vet. Anecdotally, it is often recommended that risk factors for laminitis should be minimized before and around the period of worming - e.g. for insulin resistance ensure low levels of sugar/starch in the diet and increase exercise (if the feet are correct and stable), ensure PPID is controlled, minimize stress....
Has your horse appeared to have a reaction to being wormed that worsened/brought on symptoms of laminitis? Please let us know by commenting on the forum or contacting us.
AAEP Parasite Control Guidelines 2016
Westgate Laboratories
Intelligent Worming
Diagnosteq
Anthelmintic Resistance and the Responsible Use of Anthelmintics - VMD
PPID and worms/parasites
Horses with PPID have been shown to have higher than normal worm egg counts, and an appropriate worm control programme should form part of the management plan for a PPID horse.
Christen G, Gerber V, van der Kolk JH, Frey CF, Fouché N
Fecal strongyle egg counts in horses with suspected pre-clinical pituitary pars intermedia dysfunction before and after treatment with pergolide
The Veterinary Journal May 2018 Volume 235, Pages 60-62. https://doi.org/10.1016/j.tvjl.2018.03.007 (DeepDyve)
J Am Vet Med Assoc. 2010 Feb 1;236(3):330-4. (PubMed)
Fecal egg counts after anthelmintic administration to aged horses and horses with pituitary pars intermedia dysfunction
McFarlane D, Hale GM, Johnson EM, Maxwell LK
"For similar environmental conditions, horses with PPID were more likely to have higher fecal egg counts than were healthy horses. Therefore, horses with PPID may need to have a more aggressive parasite prevention program than do healthy horses."
Is praziquantel safe for EMS/PPID horses?
TLS has seen suggestions that praziquantel should not be used for insulin resistant horses, seemingly based on this research:
Arzneimittelforschung. 1996 Apr;46(4):433-5 (PubMed)
Effect of praziquantel on serum glucose and insulin levels in normal and hyperglycemic rats
el-Kashef HA, Salem HA, Said SA, Elmazar MM.
"The effects of praziquantel (CAS 55268-74-1) on serum glucose and insulin levels in normoglycemic and hyperglycemic rats were studied. Also the combined effect of praziquantel and glibenclamide (CAS 10238-21-8) on oral glucose tolerance in rats was investigated. Praziquantel, given orally in a dose of 250 mg/kg, significantly increased serum glucose level in hyperglycemic rats without changing serum insulin level. After oral glucose load, praziquantel produced a significant increase in serum glucose level and antagonized the hypoglycemic action of glibenclamide. These results indicate that praziquantel significantly increased serum glucose level in both hyperglycemic rats and after glucose load. Since insulin levels are not significantly altered by praziquantel, the hyperglycemic effect of this drug may be attributed to inhibition of peripheral glucose utilization. Care should be taken if praziquantel is prescribed to diabetic patients."
The dose of praziquantel used in this research was 250 mg/kg bodyweight (BW) in rats - 100 x the highest dose used in any horse wormer -
Doses of praziquantel in horse wormers:
Equest Pramox 2.5 mg/kg BW
Equimax 1.5 mg/kg BW
Eqvalan Duo 1 mg/kg BW
Equitape 1 mg/kg BW (Equitape is discontinued from sale in the UK from October 2018)
In the research, praziquantel only increased basal serum glucose levels in rats that already had above normal glucose levels - no mention is made of praziquantel increasing glucose levels in the normoglycaemic rats. The serum insulin level was not changed. The serum glucose level was increased when an oral glucose tolerance test was carried out on rats given praziquantel, presumably this was in both hyperglycaemic and normoglycaemic rats. Therefore it might be sensible to avoid carrying out an oral glucose test or giving an exceptionally large amount of glucose to any horse within a few days of using Praziquantel.
Insulin resistant horses do not generally have above normal glucose levels.
We have not found any advice that diabetic/hyperglycaemic humans should avoid or take special care with praziquantel - datasheets for Biltricide (praziquantel for human use) do not appear to mention diabetes or hyperglycaemia.
We have been unable to find any evidence suggesting that praziquantel should be avoided for horses with insulin resistance. As always, if you have any concerns, please discuss with your vet.
Adverse effects of worming
There are anecdotal reports of episodes of laminitis or "footiness" following the use of anthelmintics (de-worming drugs). Post-dosing colic is likely to be attributable to parasite death, and using single-dose/single chemical wormers may be recommended to stagger parasite death:Virabac Animal Health Equine Worming Training Manual p 45:
"Equine Anthelmintic drugs on the whole have very good safety margins and primary adverse reactions are extremely rare, however, post-dosing colic is a recognized phenomenon with most drugs.
When it does occur, colic is usually mild and transient (spasmodic) and resolves without any treatment. It is generally accepted that this is more likely to be attributable to parasite death causing intestinal irritation rather than the drugs themselves and consequently the risk of this problem is greater in horses/ponies carrying heavier burdens."
The following adverse effects/contra-indications are from the NOAH datasheets or VMD SPCs for each wormer:
Wormers containing praziquantel:
Equitape - "In horses with severe infections, treatment may result in mild, transient colic and loose faeces due to the destruction of the tapeworms." (As at 2021 no Equitape is no longer being made, but praziquantel may be available through your vet - see Westgatelabs.co.uk).
Equimax (paste) - "Some horses carrying heavy infection of Onchocerca microfilariae have experienced reactions with swelling and itching after treatment. It is assumed to be the result of death of large numbers of microfilariae."
Equimax tablets - "Colic, diarrhoea and anorexia have been reported in very rare occasions post treatment, in particular when there is heavy worm burden. In very rare occasions, allergic reactions such as hypersalivation, lingual oedema and urticaria, tachycardia, congested mucus membranes, and subcutaneous oedema have been reported following treatment with the product."
Eqvalan Duo - "Some horses with heavy infections of Onchocerca spp. microfilariae have experienced oedema and pruritus following treatment, assumed to be the result of the death of large numbers of microfilariae. These signs resolve within a few days but symptomatic treatment may be advisable. In cases of heavy infestations with tapeworms, signs of mild, transient colic and diarrhoea may be observed. Following administration of EQVALAN DUO, there have been rare reports of inflammation of the mouth, lip and tongue, which results in various clinical signs such as oedema, hypersalivation, erythema, tongue disorder and stomatitis. These reactions have been transitory in nature, appearing within 1 hour and abating within 24 to 48 hours following administration. In case of severe oral reactions symptomatic treatment is recommended."
Equest Pramox - "Mouth pain, flaccid lower lip, swelling of the muzzle, hypersalivation and anorexia have been observed in rare cases. Ataxia has been reported on rare occasions and lethargy in very rare cases. These adverse effects are transient and disappear spontaneously. In case of very high worm burdens, destruction of the parasites may cause a mild transient colic and loose faeces in the treated horse."
Datasheets for other worming chemicals can be found on the NOAH website or Veterinary Medicines Directorate Product Information Database (UK).
Worming programmes for horses that may be at high risk of high worm burdens or that have had laminitis or been diagnosed with EMS or PPID should be discussed with a vet. Anecdotally, it is often recommended that risk factors for laminitis should be minimized before and around the period of worming - e.g. for insulin resistance ensure low levels of sugar/starch in the diet and increase exercise (if the feet are correct and stable), ensure PPID is controlled, minimize stress....
Has your horse appeared to have a reaction to being wormed that worsened/brought on symptoms of laminitis? Please let us know by commenting on the forum or contacting us.