Effects of a single day of feed restriction on changes in serum leptin, gonadotropins, prolactin, and metabolites in aged and young mares.

The research examines how a single day of food restriction influences the hormonal and metabolic profiles of older and younger horses. The experiments found that such a brief period of feeding restriction leads to a decrease in serum leptin levels, but other hormones, including several related to reproduction, did not significantly change.

Research Overview

• The research involved two separate experiments targeting older mares (over eight years old) and younger mares (below five years old) respectively to investigate the effects of a one-day feed restriction on hormonal and metabolic changes.
• The mares’ estrous cycles were synchronized, and they were conditioned to eat twice a day. On the seventh day after synchronization, some mares (referred to as the ‘restricted’ group) were not given food for 24 hours, while the others were fed as usual.

Key Findings

• In both groups of mares (aged and young), the restricted mares had a significant decrease in their serum leptin levels. Leptin is a hormone associated with hunger and fat storage.
• However, the study found no significant change in serum glucose concentrations (how much glucose is in the blood), regardless of the feed restriction or refeeding. This suggests that short-term food deprivation is not enough to disrupt blood glucose management in horses.
• Interestingly, an increase in free fatty acids was observed in both experiments following feed restriction. This might be due to the breakdown of fat reserves in the mares’ bodies as a response to the lack of food, releasing fatty acids into the blood.
• The levels of gonadotropins – hormones that influence reproduction, such as prolactin, FSH (follicle-stimulating hormone), and LH (luteinizing hormone) – did not significantly change following feed restriction.

Interpretation and Implications

• The unchanged levels of gonadotropins, despite a noticeable drop in leptin, suggest that the mare’s reproductive system might maintain stability during short-term feed deprivation. This could be due to the body still having sufficient metabolizable fuels (resources that can be converted into energy).
• Alternatively, the unchanged levels of reproductive hormones might mean that leptin did not signal the nutritional status to the mare’s reproductive system, despite the drop in its level due to feed restriction.
• The results of this study provide important insights into understanding the biological responses to food deprivation in mares, which can be crucial in animal management and care. Care must be taken not to attribute the reduced leptin levels solely to the feed restriction, as other factors, including stress or slight variations in the feeding schedule, could potentially influence the hormonal balance.