Effect of calcium soaps of fatty acids and administration of somatotropin in early lactation on productive and reproductive performance of high producing dairy cows

This study examined the mechanisms by which calcium soaps of fatty acids and bovine somatotropin (bST) affect production and reproduction of high producing cows. Calcium soaps of fatty acids were fed at 2.2% dry matter, and 500 mg of Zn-sometribove (Monsanto Inc., St Louis, MO) were injected subcutaneously every 14 d from 10 to 150 d in milk (DIM). Production of fat-corrected milk was increased by 3.5 kg/d when calcium soaps of fatty acids were fed, by 6.1 kg/d when bST was administered, and by 7.4 kg/d when calcium soaps of fatty acids were fed and bST was administered. Body weight was similar for cows on all treatments until 85 DIM after which cows that were treated with bST had lower body weights. Body condition scores decreased more for cows treated with bST and began increasing later and more slowly. Treatment with bST resulted in more cows that experienced first ovulation after 30 DIM, and more cows on the control treatment exhibited first estrus before 35 DIM. Days open were greater when bST was administered. After the first artificial insemination, conception rates were similar for cows on the control treatment and for cows fed calcium soaps of fatty acids; conception rates after the first artificial insemination were low for all cows treated with bST. Pregnancy rates at 120 and 150 DIM were decreased by bST. Number of DIM to first ovulation, number of DIM to first estrus, and days open were negatively correlated with glucose and cholesterol concentrations in plasma. Production of fat-corrected milk was correlated with days open and with concentrations of triglycerides in plasma, nonesterified fatty acids, and cholesterol. Increased production had different effects on reproduction when induced by calcium soaps of fatty acids or bST treatment. Some of the adverse effects of bST treatments were alleviated by calcium soaps of fatty acids.