The Role of Exogenous Bovine Somatotropin on Lactation and Nutrient Mobilization in Dairy Animals: A Review

The objective of this paper was to review the role of exogenous bST effect on lactation and nutrient mobilization. Bovine somatotropin (bST) is a protein hormone that increases milk yield in dairy animals. The role of bST is to control nutrient partitioning, coordinated change in body tissues during metabolic processes, and alterations of mammary function to support increased milk synthesis. Increasing the concentrations of insulin-like growth factors IGF-I results in increasing the rates of milk synthesis per cell and improving the maintenance of secretory cells. The maximum increase in milk production has been observed up to 41%. Nutrition, the genetic makeup of the cow, physiological condition, and level of management can affect the response of bST in milk production. Circulating bST is higher in well- managed and genetically superior cows. The feed intake of cows treated with bST changed after the 8-10 th week of treatment, and it had increased up to 13.4% by week 22. Also, bST-treated cows showed that the amount of mammary parenchyma and mammary epithelial cells during the first 6 weeks of lactation was not affected. The variation in milk composition due to bovine somatotropin injection was not significantly affected. In the early lactation stage, the cows mobilize their body reserves to support the increased milk production. The appropriate time preferred to start to use bST is at about peak milk yield of approximately around 60±3 day. Increase uptake of glucose, decreased oxidation of amino acids and stimulation of lipolysis are the major effect of bST during nutrient metabolism. Bovine somatotropin doesn’t have any significant adverse effect on human health; also it doesn’t affect the health and reproductive performance of the cows. Therefore, the application of bST improves dairy productivity; it makes the producers more profitable, satisfies the milk demand, and improves the livelihood of the community.