Effect of prolactin infusion on lactation, glucose kinetics, and pancreatic hormones in lactating goats

To determine lactational and glucogenic responses to increased prolactin concentrations, five lactating dairy goats were used in a crossover design. Prolactin at .85 mg/h or placebo was infused on each of 8 consecutive d via jugular catheter for 14 h initiated 30 min after the a.m. milking. To examine the effect of treatments on glucose metabolism, goats were given a single isotope injection of [6-3H]glucose 2 h after initiation of treatment infusion on the final day of the treatment period. Milk yield and milk protein percentage were not affected by prolactin infusion; however, milk fat and SNF percentage were significantly decreased. No differences in dry matter intake and digestibility of the diet were observed. Prolactin increased plasma prolactin and decreased plasma glucagon concentrations, but did not affect plasma insulin or glucose concentrations. Although glucose pool size per kilogram of BW was significantly lower in the prolactin-treated group than in the control group, no difference in glucose turnover rate was observed.