Performance and Nutrient Digestibility by Dairy Cows Treated with Bovine Somatotropin and Fed Diets with Steam-Flaked Sorghum or Steam-Rolled Corn During Early Lactation

¹ Department of Animal Sciences, University of Arizona, Tucson 85721-0038

This study compared effects of exogenous bovine somatotropin (bST) on the performance of early lactation cows fed diets differing in ruminally degradable starch. Thirty-two Holstein cows (24 multiparous) in early lactation (5 d in milk) were divided into four groups and fed diets containing 39% grain as steam-flaked sorghum or steam-rolled corn with or without exogenous bST for 90 d. Grain processing did not affect dry matter intake as a percentage of body weight or yields of milk, but steam-rolled corn improved efficiency of feed utilization during the first 45 d of the study. Cows receiving bST had lower dry matter intake during the first 45 d of treatment. Milk yield and efficiency of feed utilization were increased by bST treatment, and milk yield response was greater during the first half than during the second half of the study. Milk composition and yield of milk components did not differ among treatments. Flaked sorghum increased in vitro starch hydrolysis and digestibilities of dry matter, organic matter, and starch, but neither method of grain processing nor bST affected digestibilities of crude protein, acid detergent fiber, or neutral detergent fiber. Grain type did not affect milk yield, and responses to bST were lower from 7 to 13 wk than from 1 to 6 wk prepartum.

Key Words: bovine somatotropin • early lactation • processed grains

Submitted on April 23, 1998
Accepted on October 13, 1998

This article has been cited by other articles:

				M. Carriquiry, W. J. Weber, and B. A. Crooker Administration of Bovine Somatotropin in Early Lactation: A Meta-Analysis of Production Responses by Multiparous Holstein Cows J Dairy Sci, July 1, 2008; 91(7): 2641 - 2652. [Abstract] [Full Text] [PDF]