Leptin concentration in plasma and in milk during the interpartum period in the mare.

The research aimed to examine how varying concentrations of leptin, a hormone regulating appetite, and estradiol, a form of estrogen, in both blood and milk of mares (adult female horses) change during different stages of their reproductive cycle. It was found that the concentrations fluctuated over time, and at certain stages leptin concentration in milk was higher than in blood, potentially indicating a role in mammary gland functioning or foal (young horse) intestinal development.

Objective of the Research

• The research primarily targeted to determine the shifting levels of leptin and estradiol 17beta throughout the interpartum period (the period between two deliveries) of mares.
• The concentrations of leptin and estradiol 17beta in colostrum (first form of milk usually rich in antibodies and nutrition) and regular milk were measured and compared against their corresponding plasma concentrations.

Leptin Measurement Findings

• After the first delivery, leptin concentration in plasma was 5.1±2.3 ng/ml.
• This dropped to 3.0±0.7 ng/ml by the 21st week, then rose to a maximum level of 6.9±1.0 ng/ml at week 49.
• Leptin concentrations in the colostrum and milk were found to be significantly higher than in plasma samples at week 1, as well as between weeks 12 and 17 of this period.
• The higher concentration of leptin in milk compared to plasma implies that leptin is locally produced at the mammary level, validating its important role in the mammary gland or in the development of the foal’s intestine.

Estradiol Measurement Findings

• The concentration of this estrogen hormone increased from 17.9±2.3 pg/ml at week 15 to 487.9±67.7 pg/ml by week 43.
• The rise in estradiol 17beta in the plasma was observed to precede the increase of plasma leptin by about 4 weeks.
• However, estradiol 17beta does not seem to have a positive correlation with leptin secretion.