Ovarian activity and estrus behavior in early postpartum cows grazing Leucaena leucocephala in the tropics

The legume Leucaena leucocephala (Leucaena) is widely used to supplement forage in silvopastoral livestock systems in Latin America. Little is known about its possible effects on the cow reproductive dynamic. The aim was to evaluate the effect of Leucaena foliage intake on re-establishment of ovarian activity and estrus behavior in early postpartum (7-90 days) cows. Twenty-four multiparous Bos taurus × Bos indicus cows were divided into two homogenous groups and assigned to one of two treatments: a silvopastoral system (SS, n = 12), consisting of an association of Cynodon nlemfuensis grass and L. leucocephala; and a control system (CS, n = 12), consisting of C. nlemfuensis alone. Intake of Leucaena in the SS ranged from 3.80 to 6.43 kg DM/cow/day. Plasma mimosine concentrations ranged from 1270 to 1530 μg/mL, and those for 2,3-dihydroxypyridine (DHP) from 147 to 729 μg/mL. No 3,4-DHP was detected in plasma. No difference (P > 0.05) between treatments was observed for the number of cows exhibiting small, medium, or dominant follicles, or estrus behavior. The number of cows which re-established ovarian cyclicity (n = 6) was lower (P < 0.05) in the SS than in the CS (n = 9). Corpus luteum lifespan was longer (P < 0.05) in the SS than in the CS. Intake of Leucaena affected the number of cows exhibiting ovarian cyclicity and extended corpus luteum life, but did not affect follicular development and estrus behavior.