title: Lactation, health, and reproduction of dairy cows receiving daily injectable or sustained-release somatotropin.
abstract: Seventy-four Holstein cows (26 primiparous) were utilized to compare the efficacy and safety of sustained-release versus daily injectable formulations of recombinant bST. Twenty-four control cows were injected biweekly with oil microsphere; 25 cows were injected biweekly with 350 mg of bST microsphere; and 25 cows were injected daily with 10.3 mg of bST. Injections were initiated between wk 4 and 5 of lactation and continued for 280 d. Administration of bST caused a moderate increase in milk and FCM production and improved the efficiency of feed and energy conversions. Most health-related and reproduction-related variables did not differ among treatment groups. However, incidence of teat and udder disorders and feet and leg problems tended to be higher during the 40-wk injection period for the bST-treated cows than for the control cows. Incidence of GnRH therapy and number of days to first service were higher for daily bST-treated cows than for controls. No differences existed between sustained-release and daily bST-treated cows for any parameters monitored.
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, ON, Canada.
authors.forename: X
authors.initials: X
authors.lastname: Zhao
authors.forename: J H
authors.initials: JH
authors.lastname: Burton
authors.forename: B W
authors.initials: BW
authors.lastname: McBride
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D003692:Delayed-Action Preparations; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007279:Injections, Subcutaneous / Q000662:veterinary; D007774:Lactation / Q000187:drug effects*; D016014:Linear Models; D012098:Reproduction / Q000187:drug effects*
chemical_list: D003692:Delayed-Action Preparations; D013006:Growth Hormone