Factors affecting response of cows to recombinant methionyl bovine somatotropin
AdvisorHuber, John T.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractEighty lactating Holstein cows were randomly assigned to one of two treatments: Placebo(C) or 500 mg recombinant methionyl bovine somatotropin (BST). Cows were intramuscularly injected with C or BST every 14 d for 36 wk beginning 60 d postpartum. Factors analyzed for differences in milk yield response to BST included: production level, genetic potential, stage of lactation, and heat stress. Response of low producing cows to BST was numerically greater than that of medium or high producers (averaging 27%, 13%, and 20%, respectively, above controls). However, there was not a significant interaction between BST treatment and production group. Cows of a lower genetic potential exhibited a greater response to BST than cows of a higher potential, but the treatment x genetic potential interaction was not significant. Response of cows to BST in mid to late lactation was slightly greater than in cows in early lactation (13.7% and 15.1% vs. 9.6%, respectively) but no significant interaction was noted. No difference in response was noticed during periods of high ambient temperature.
Degree ProgramGraduate College