Plasma Prolactin, Blood Metabolites and Yield and Composition of Milk during Early Lactation in Goats Following Administration of Bromocryptine

Six crossbred goats in their 2nd or 3rd lactation, were administered bromocryptine at 5 mg/day during early lactation of 15-20 days (period I) and thereafter again at an interval of 13 days, bromocryptine was given for 5 days (period II). Blood samples were collected before (-5, -4, -3, -2, -1) during (1, 2, 3, 4, 5) and after (+1, +2, +3, +4, +5) administration of bromocryptine in both the periods of study. In period I, administration of bromocryptine resulted in a decrease in milk yield to the extent of 16..8% in comparison to before treatment, and 28.5% after the cessation of treatment. The glucose content of blood increased (p<0.01) as the milk yield decreased without any change in NEFA concentration. During period II of bromocryptine treatment the milk yields did not change in spite of a decline in prolactin level, perhaps the effect of previous treatment was prolonged. A decline in protein and lactose content of milk after bromocryptine treatment in both the periods of study, when prolactin level also declined suggests a role of prolactin in protein synthesis and also a depressing effect on lactose synthesis.