Comparative study of progesterone levels in milk and plasma in sheep

Abstract

The ovine production tends to be intensified and new productive alternatives are being explored. In order to improve the reproductive efficiency, plasma Progesterone (P) determination is a tool used for measuring ovarian activity. Our objective was to measure the P levels in blood and milk simultaneously and correlate them. Six anestrous sheep were injected i.m. with P )0.4 mg/kg body weight) in oil vehicle. Blood and milkwere tken 2, 4, 6, 12, 18, 24, 30, 36, 42 and 48 hr after the progesterone injection and progesterone levels were determined by radioimmunoassay (RIA) validated for plasma and milk. The P levels at 0 hr were basal, but at 2 hr they increased significantly, and reached maximum levels at 6 and 12 hr in plasma and milk, respectively. The levels returned to basal concentrations ar 42 and 30 hr in plasma and milk, respectively. The correlation between P concentration in plasma and milk was highly significant and positive (r=0.858; n=66; p<0.0001, indicating that milk P determinations are representative of the blood levels and it can be used for non-invasive monitoring of the reproductive processes.