Effects of grazing system, season, and forage carbohydrates on glucose and insulin dynamics of the grazing horse.
J Anim Sci. 2019 May 30;97(6):2541-2554. doi: 10.1093/jas/skz103. PMID: 30911753; PMCID: PMC6541809.
Keywords: carbohydrate, continuous grazing, equine, glucose, insulin, rotational grazing
3 research periods - 10-11 June, 12-13 August, 14-15 October 2015.
Cool season grass (tall fescue, Kentucky bluegrass, orchardgrass) paddocks were either grazed continuously (CON) or by rotation (ROT), meaning that horses grazed the ROT paddocks when grass was >15.2 cm and were removed to a dry lot with hay when grass was grazed to 7.6 cm. Before each study period ROT horses had been grazing for >8 days.
12 Standardbred mares, mean age 14, start BCS 6.1/9 were paired by age and weight and randomly assigned to either CON or ROT in August 2014.
The night before the blood collection in each study period the horses were stalled with grass hay to obtain a baseline sample at 08:00, then let out to graze, with blood and faeces collected every 4 hours until 08:00 the following morning, for a total of 7 samples. Grass was sampled at the same times. In ROT grass was hand cut at 10.2 cm high, in CON grass was cut just above ground level, to reflect the grass being grazed. Grass was stored on dry ice and sampled by wet chemistry at Equi-Analytical.
Sward height, weather and faeces pH were also recorded.
Plasma glucose was analysed by Glucose C-2 colorimetric assay, serum insulin by Mercodia ELISA with results reported in micrograms/L.