Somatotropin increases plasma ceramide in relation to enhanced milk yield in cows

Recombinant bovine somatotropin (rBST) changes metabolism to spare glucose for milk synthesis in cows. Ceramides inhibit insulin responsiveness in bovine adipocytes and are associated with insulin resistance and milk production in cows. The mechanisms by which rBST supports lactation may involve ceramide. Eight multiparous lactating Holstein cows were enrolled in a 2 × 2 replicated Latin square design with 14-d periods. Cows received a single rBST injection (Posilac; Elanco Animal Health, Indianapolis, IN; 0.062 mg/kg BW) or no injection (CON). An epinephrine challenge, insulin tolerance test, and liver biopsy were performed. Somatotropin enhanced the conversion of feed nutrients into milk components and increased plasma free fatty acid (FFA) concentrations (P < 0.01). Area-under-the-curves for FFA in response to epinephrine and insulin were greater in rBST-treated cows. In response to insulin, glucose concentrations (20- and 30-min post-challenge) and insulin area-under-the-curve were higher with rBST treatment (P < 0.05