title: Ardacin for steers grazing endophyte-free fescue pasture: effects on live weight gain, forage intake, nitrogen and fiber digestion, ruminal fluid kinetics, ruminal fermentation, and serum hormones and metabolites.
abstract: Growth and digestion studies were conducted to evaluate the use of ardacin as a feedgrade antibiotic for enhancing digestive function and growth in grazing steers. In Exp. 1, 90 yearling steers (average initial BW of 248 kg) used in a randomized complete block design (block = weight group) grazed fescue pasture without supplementation (CON) or with daily supplements (DM basis) of .4% of BW supplemental ground corn (CRN) or .4% of BW supplemental corn supplying 120 mg of ardacin (ARD). In Exp. 2, 12 ruminally and duodenally cannulated steers and three ruminally cannulated steers (Hereford x Angus; average BW of 347 kg) were used to evaluate the effects of the same supplements used in Exp. 1 on ruminal fermentation and digestion. In Exp. 1, ARD-supplemented steers weighed more (P < .01) at the conclusion of the study than CRN steers, which together weighed more (P < .01) than CON steers. Average daily gain was greater (P < .10) in supplemented than in CON steers; ARD steers had greater (P < .01) ADG than CRN steers. In Exp. 2, forage intake and harvesting efficiency did not vary (P > .10) with supplementation or type of supplement, but total intake reflected (P = .03) the addition of corn to the forage diet. Addition of ardacin increased (P = .02) ruminal pH compared with CRN steers. Ardacin decreased ruminal molar proportions of acetate and increased (P = .01) propionate proportions when compared with CRN steers. Total tract N digestibility was affected (P < .10) by supplementation and by addition of ardacin to the diet. Addition of ardacin to the ground corn supplement increased ADG, in part by enhancing acetate:propionate ratios and increasing N digestion.
authors.affiliation: School of Veterinary Medicine, University of Nevada, Reno 89557-0104, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Judkins
authors.forename: D W
authors.initials: DW
authors.lastname: Holcombe
authors.forename: B W
authors.initials: BW
authors.lastname: Hess
authors.forename: L J
authors.initials: LJ
authors.lastname: Krysl
authors.forename: M A
authors.initials: MA
authors.lastname: Branine
authors.forename: J D
authors.initials: JD
authors.lastname: Hess
mesh_terms: D000617:Aminoglycosides; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001786:Blood Glucose / Q000378:metabolism*; D001806:Blood Urea Nitrogen; D001835:Body Weight / Q000187:drug effects* / Q000502:physiology; D002417:Cattle / Q000097:blood / Q000378:metabolism* / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004043:Dietary Fiber / Q000378:metabolism*; D004063:Digestion / Q000187:drug effects* / Q000502:physiology; D004435:Eating / Q000187:drug effects* / Q000502:physiology; D005285:Fermentation / Q000187:drug effects / Q000502:physiology; D005527:Food, Fortified; D013006:Growth Hormone / Q000097:blood*; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D051381:Rats; D012417:Rumen / Q000187:drug effects* / Q000502:physiology; D013963:Thyroid Hormones / Q000097:blood*; D013997:Time Factors; D015430:Weight Gain / Q000187:drug effects* / Q000502:physiology; D003313:Zea mays / Q000592:standards
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D001786:Blood Glucose; D004043:Dietary Fiber; D007328:Insulin; D013963:Thyroid Hormones; C069893:ardacin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D009584:Nitrogen