Lactational Response to Exogenous Growth Hormone and Abomasal Infusion of a Glucose- Sodium Caseinate Mixture in High-Yielding Dairy Cows1 COLIN J. PEEL,2 THOMAS J. FRONK,3 DALE E. BAUMAN4 ANDRONALD C. GOREWIT Department of Animal Science, Cornell University, Ithaca, NY 14853-0281 ABSTRACT Milk production responses to 1) growth hormone injections (51.5 ID/ day), 2) a mixture of glucose (274 g/day) and sodium caseinate (441 g/day) infused into the abomasum, 3) a combination treatment, and 4) a placebo treatment were determined in 4 cows in a 4 X 4 Latin square design. Treatment periods were 10 days, and production responses were based on the last 5 days of each treatment. Growth hormone administration increased milk yield 15.2% without changing milk composition or feed intake. Infusions of glucose-sodium caseinate into the abomasum increased milk yield 3.9% and milk protein yield 6.4% but when combined with growth hormone treatment did not stimulate a greater response than observed for growth hormone alone. Plasma concentrations of growth hormone were increased 4-fold with growth hormone injections but were not affected by the infusion of glucose-sodium caseinate into the abomasum. There were no significant changes in plasma concentrations of glucose, free fatty acids, insulin, glucagon, prolactin, triiodothyronine, thyroxine or cortisol with any of the treatments. Growth hormone increased milk synthesis and the efficiency of milk production, but its effect was not enhanced by the postruminal supply of additional nutrients. J. Nutr. 112: 1770-1778, 1982. INDEXING KEY WORDS growth hormone •casein •milk composition • milk yield The synthesis of milk in the epithelial cell and fatty acids (4) have been made available of the mammary gland requires a complex to the mammary epithelial cells. Glucose is interaction between the major substrates for also an essential substrate for milk synthesis, milk synthesis, acetate, glucose, amino acids providing not only carbon for the synthesis and fatty acids, and a multitude of regulatory of lactose, but also a significant portion of the hormones. These hormones include insulin, energy required for the synthesis of milk fat prolactin, growth hormone and the thyroid hormones, which are all important in main- . . . .11 .. /,\ »T i. ©1982 American Institute of Nutrition. Received for publication 1 April taming milk secretion (1). Numerous studies I982 have attempted tO enhance normal milk Se- ' Supported in part by Cornell University Agricultural Experiment Sta- hv pithpr hvnassini* ruminai fprmpn- lion> The UP'ohn Company. US Department of Agriculture/Science and " lllg rum ii Education Administration-Agricultural Research Dairy Forage Cluster. , thus Supplying additional nutrients for and National Science Foundation grant PCM811)8130 Portions of this paper .11 .1 i i . . . were presented at the 75th Annual Meeting of the American Dairy Science milk Synthesis, Or by administering eXOge- Action ¡„ Baton Rouge, Louisiana. 1981.Abstrac.no. P132. and a. the nOUS hormones tO elevate Circulating plasma C0."16'1 Nutrition Conference in Syracuse. NY. 1981. r , . 'On leave from Victorian Department of Agriculture, Kilink.uk Dairy Concentrations OI these nutrients. Research Institute, Warragul. Victoria 3820, Australia. Increases in milk production have been c^^H"g™ c""""ionMillin* DivWon- **E"tMiU*""•a" obtained when additional amino acids (2, 3) «Authorto whom reprint requests should be addressed 1770 by guest on August 3, 2015 jn.nutrition.org Downloaded from