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

The aim of this work is to investigate on plasma profiles of leptin and estradiol 17β during the interpartum period and leptin concentrations in the milk and in the colostrum during the period from parturition to the successive delivery in mare. Leptin plasma concentration varied from 5.1 ± 2.3 ng/ml after the first parturition (week 0) to 3.0 ± 0.7 at week 21 (p < 0.05), then it increased to maximal level at week 49 (6.9 ± 1.0 ng/ml, p < 0.05). Leptin concentration in the colostrum and in the milk has been significantly (p < 0.05) higher than that in plasma samples at week 1 (milk 8.8 ± 2.3 versus plasma 5.2 ± 0.6 ng/ml) and between week 12 and 17. This difference may be explained with a local leptin production at mammary level and supports a role of leptin in the mammary gland and/or in foal intestine. Estradiol 17β increased from week 15 (17.9 ± 2.3 pg/ml) up to 487.9 ± 67.7 pg/ml at week 43. Plasma estradiol 17β rise anticipated by 4 weeks plasma leptin increase and it does not seem to be positively correlated to leptin secretion.