Milk and blood progesterone concentration in ewes (Ovis aries) under different physiological states and progestogen treatment

Abstract

ABSTRACTThe aim of this study was to quantify the concentration of milk and blood progesterone (P4) from lactating ewes under different physiological states and the possible harmlessness of their milk in human consumption. Progesterone concentration was determined in ovariectomized and intact ewes during the oestrous cycle, while implanted with a controlled internal drug release (CIDR) containing 0.3 g of natural P4 (OxCIDR; ICIDR) or not (Ox; I), and during pregnancy (G). Mean P4 concentration was found to be significantly greater in blood (P > 0.0001) than in milk sources. Concentrations also varied according to treatments (P < 0.0001). As expected, P4 concentration from Ox ewes was the lowest compared to the rest of the treatments (0.31 ± 0.22 ng ml−1; P < 0.0001). Ewes with CIDR showed greater P4 concentration than the respective group without implant (OxCIDR vs. Ox; P < 0.0001, and ICIDR vs. I; P < 0.01). In addition, G ewes showed the highest P4 concentration when compared with the rest of the treatments (P < 0.03). There was an interaction between P4 source and treatment (P < 0.0001). It was concluded that as milk of cycling and G animals is considered safe for human consumption, then the milk of CIDR-treated ewes should also be considered safe, based on P4 concentration.