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

Abstract

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 ngmL -1 ) and CORT (12.5 vs. 11.5 ngmL -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 pgmL -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. oxytocin / prolactin / cortisol / milking / suckling / ewes Rsum -Effet de la conduite mixte sur la dcharge d'ocytocine, de prolactine et de cortisol lors des traites et ttes journalires chez la brebis. La production laitire et les concentrations en ocytocine (OT), prolactine (PRL) et cortisol (CORT) ont t mesures chez 12 brebis multipares lors d'une conduite mixte d'allaitement/traite (3 ttes et 2 traites journalires). La quantit moyenne de lait obtenue la tte (632 mL) est suprieure celle obtenue lors des traites (255 mL). Entre traites et ttes, des dcharges significatives mais non diffrentes ont t enregistres pour PRL et CORT (181 vs. 163.3 ngmL -1 et 12.5 vs. 11.5 ngmL -1 respectivement). La dcharge d'ocytocine n'est significative que durant les ttes et est inexistante durant les traites (91.7 vs. 13.1 pgmL -1 ) alors qu'elle est prsente aux mmes horaires lors de la tte exclusive. Les dcharges de PRL, CORT et OT peuvent donc tre dcouples prouvant l'existence d'un contrle central diffrent. L'absence de dcharge d'ocytocine la traite fait que la conduite mixte n'est pas efficace pour adapter physiologiquement les brebis la traite mcanique avant le sevrage.