title: Influence of forage level and naloxone injection on feed intake, digestion, and plasma hormone and metabolite concentrations in dairy heifers.
abstract: Four ruminally cannulated Holstein heifers (287 +/- 26 kg) in a 4 x 4 Latin square were used to evaluate the effects of naloxone injection and forage level on dietary intake, ruminal fermentation characteristics, digestibility, and plasma hormone and metabolite concentrations. Treatments were arranged in a 2 x 2 factorial with naloxone injection (0 vs .3 mg/kg; saline vs naloxone, respectively) and forage level (20 vs 100%; concentrate vs forage) as factors. Stanchioned heifers were allowed 21 d for adaptation before a 5-d collection period. Plasma samples were collected several times on d 1 and daily at 0730. Concentrate-fed heifers consumed more feed (P < .10) than forage-fed heifers. Naloxone injection decreased (P < .10) feed intake (grams/kilogram BW) at 1 and 2 h after feeding on d 1. On d 3 at 24 h after feeding, naloxone-injected heifers had increased DM (P < .10) intakes compared with control (saline-injected) heifers. Concentrate-fed heifers had decreased (P < .10) ruminal pH and increased total ruminal VFA concentration. Acetate proportion was decreased (P < .10) and propionate proportion increased in concentrate-fed heifers. Naloxone-injected heifers had decreased (P < .10) total VFA concentrations and increased propionate proportions. Concentrate-fed heifers had greater (P < .10) DM, OM, and CP digestibilities as well as increased plasma (P < .10) insulin, urea N, and glucose concentrations but decreased (P < .10) GH and NEFA concentrations. Naloxone injection increased (P < .10) plasma insulin concentration. Naloxone injection in dairy heifers reduces intake up to 2 h after injection, alters ruminal fermentation patterns, and increases plasma insulin concentration.
authors.affiliation: Department of Animal and Range Sciences, North Dakota State University, Fargo 58105, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Burgwald-Balstad
authors.forename: J S
authors.initials: JS
authors.lastname: Caton
authors.forename: V I
authors.initials: VI
authors.lastname: Burke
authors.forename: K C
authors.initials: KC
authors.lastname: Olson
mesh_terms: D000821:Animal Feed / Q000145:classification; D000818:Animals; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000502:physiology*; D003612:Dairying; D004063:Digestion / Q000187:drug effects* / Q000502:physiology; D004435:Eating / Q000187:drug effects* / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005285:Fermentation; D013006:Growth Hormone / Q000097:blood; D006863:Hydrogen-Ion Concentration; D007267:Injections; D007328:Insulin / Q000097:blood; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D009292:Narcotic Antagonists; D009270:Naloxone; D013006:Growth Hormone