The effect of a mixed-management system on the release of oxytocin, prolactin, and cortisol in ewes during suckling and machine milking

Overview & Synopsis

Milk yield and plasma oxytocin (OT), prolactin (PRL), and cortisol (CORT) during suckling and machine milking were measured in multiparous ewes subjected to a mixed management system of 3 sucklings and two daily milkings. Peak hormones were significantly increased and were similar during suckling and milking for PRL (181 vs. 163.3 ng$\cdot$mL$^{-1}$) and CORT (12.5 vs. 11.5 ng$\cdot$mL$^{-1}$). During the period of exclusive suckling, OT was always significantly released (90.3 pg.mL-1); however, during the period of mixed management, OT concentrations only increased during suckling compared to milking (91.7 vs. 13.1 pg$\cdot$mL$^{-1}$). The mean volume of milk obtained during suckling (632 mL) was significantly higher than during milking (255 mL). Thus, during a mixed management system, oxytocin and prolactin releases are not under similar central regulation. A mixed system, without OT release during milking, does not contribute to accelerate the conditioning of ewes for machine milking.