Feed deprivation of mares: plasma metabolite and hormonal concentrations and responses to exercise.

The research paper investigates the effects of feed deprivation on blood metabolite and hormone levels, as well as responses to exercise, in mares. The results revealed that lack of feed led to changes in certain blood metabolites and hormones, and influenced the animals’ physiological response to exercise.

Research Methodology

• The research involved twelve light horse mares that were all initially fed a control diet proportional to their maintenance protein and energy requirement for 7 days.
• Thereafter, the mares were either maintained on the control diet or totally deprived of feed (except for access to water) for a period of 3 days.
• Blood samples were drawn from all the mares twice a day throughout the experiment, at intervals during 45 hours after feed removal, and around an exercise bout beginning 73 hours after feed removal.

Findings of the Research

• The study found that feed deprivation led to an increase in the horses’ whole blood beta-hydroxybutyrate and plasma NEFA (non-esterified fatty acids), urea nitrogen, L-lactate, and glucagon concentrations.
• Meanwhile, feed deprivation resulted in a decrease in Insulin-like growth factor-1 (IGF-1) concentrations in the mares’ blood, but had no significant impact on plasma glucose insulin, prolactin, triiodothyronine, and thyroxine concentrations.
• The mares’ response to exercise also varied based on their feeding condition. For all the mares, exercise led to an increase in plasma NEFA, prolactin, and growth hormone (GH) concentrations.
• However, the response in plasma NEFA and glucose concentrations after exercise varied between the fed mares and those that were feed-deprived. NEFA concentrations remained high after exercise in fed mares but decreased swiftly in deprived mares. By contrast, glucose concentrations increased post-exercise in deprived mares but decreased in fed mares.
• The study also noted a variation in the plasma prolactin response to exercise between the two groups of mares.

Conclusion from the Research

• Overall, the study concluded that feed-deprived mares had higher plasma GH concentrations before exercise (73 hours post feed withdrawal) and had a greater GH peak after the initiation of exercise.
• This increase in growth hormone secretion due to lack of feed was found to be similar to that reported in other domestic species, although not as large in scale.