title: Effect of sometribove on rumen fermentation, rate of passage, digestibility, and milk production responses in dairy cows.
abstract: Six ruminally and duodenally fistulated Holstein cows 60 d postpartum were assigned randomly to each of two treatments in a single reversal design. Treatments consisted of placebo or 25 mg of sometribove (bST) injected daily. Treatments were initiated at 60 d +/- 7 postpartum and maintained for 6 wk with a 3-wk adjustment between treatment periods. All cows received a TMR consisting of 16% CP and 1.67 Mcal of NE I/kg of DM. Influence of bST on rumen fermentation characteristics, digesta rate of passage, apparent nutrient digestibility, and milk production was evaluated. Milk yield of treated animals was 4.0 kg/d higher than controls. The 3.5% FCM and milk production efficiency (3.5% FCM/DMI) were significantly higher in treated animals than in controls (29.0 vs. 25.4 kg/d and 1.38 vs. 1.21 kg/kg, respectively). Percentage of rumen cellulolytic bacteria (of total viable bacteria) was not significantly different for bST-treated animals (6.4 vs. 3.4%). Total number of rumen protozoa tended to be higher (7.25 vs. 6.55 x 10(3)/ml) in bST-treated animals. Ruminal percentages of CP, NH3 N, alpha-amino N, VFA, and pH were unaffected by treatment. Sometribove treatment did not significantly affect liquid dilution or solids turnover rates. Percentages of CP, alpha-amino N, and NH3 N content in duodenal samples were unaffected by treatment. Total tract apparent digestibility of nutrients and mean daily DMI were unaffected by treatment.
authors.affiliation: Department of Animal Science, Utah State University, Logan 84322-4815.
authors.forename: M D
authors.initials: MD
authors.lastname: Winsryg
authors.forename: M J
authors.initials: MJ
authors.lastname: Arambel
authors.forename: B A
authors.initials: BA
authors.lastname: Kent
authors.forename: J L
authors.initials: JL
authors.lastname: Walters
mesh_terms: D000818:Animals; D001419:Bacteria / Q000187:drug effects; D002417:Cattle / Q000502:physiology*; D004063:Digestion / Q000187:drug effects*; D005260:Female; D005285:Fermentation / Q000187:drug effects; D013006:Growth Hormone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D006728:Hormones / Q000008:administration & dosage / Q000494:pharmacology; D019382:Human Growth Hormone; D007279:Injections, Subcutaneous / Q000662:veterinary; D007774:Lactation / Q000187:drug effects*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D012417:Rumen / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology
chemical_list: D006728:Hormones; D011994:Recombinant Proteins; D019382:Human Growth Hormone; D013006:Growth Hormone