title: Effects of calf weaning age and subsequent management systems on growth performance and carcass characteristics of beef steers.
abstract: Brahman × British crossbred steers (n = 40 and 38 in yr 1 and 2, respectively) were used to evaluate the effects of calf management systems following early weaning (EW) on growth performance, muscle gene expression, and carcass characteristics. On the day of EW (d 0), steers were stratified by BW and age (95 ± 14 kg; 74 ± 14 d) and randomly assigned to a control treatment that was normally weaned (NW) on d 180 (n = 10 steers/yr) or to 1 of 3 EW treatments: 1) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 180 (EW180; n = 10 steers/yr), 2) EW and limit fed a high-concentrate diet at 3.5% of BW (as-fed basis) in drylot until d 90 and then grazed on bahiagrass pastures until d 180 (EW90; n = 10 steers/yr), or 3) EW and grazed on annual ryegrass pastures until d 60 (yr 1; n = 10 steers) or 90 (yr 2; n = 8 steers) and then on bahiagrass pastures until d 180 (EWRG). Early-weaned steers on ryegrass and bahiagrass pastures were supplemented with high-concentrate diet at 1.0% of BW (as-fed basis) until d 180. From d 180 to 270 (yr 1), all EW steers remained in their respective treatments, whereas NW steers were provided high-concentrate diet at 1.0% of BW (as-fed basis) on bahiagrass pastures. In yr 1, feedlot finishing period began on d 270. In yr 2, the study was terminated on d 180. In both years, EW180 steers were heaviest (P < 0.0001) on d 180. On d 180 of yr 1, EWRG steers were lightest (P < 0.0001) and EW90 steers were heavier (P = 0.05) than NW steers, whereas EW90, EWRG, and NW steers had similar BW on d 180 of yr 2 (P ≥ 0.14). On d 90, muscle PPARγ mRNA expression tended (P = 0.07) to be greater for EW180 steers and was greater (P = 0.008) for EW90 vs. EWRG steers but similar (P = 0.25) between EW180 and NW steers. On d 180, PPARγ mRNA was greater (P ≤ 0.06) for EW180 vs. NW, EW90, and EWRG steers. From d 274 to 302, EW180 steers had the least ADG (P ≤ 0.09), whereas EW90 steers had similar (P = 0.19) ADG compared with EWRG steers but greater (P = 0.03) ADG than NW steers. At slaughter, carcass characteristics did not differ (P ≥ 0.22) among treatments. In summary, EW steers provided a high-concentrate diet in drylot for at least 90 d were heavier at the time of normal weaning than NW steers and EW steers grazed on ryegrass pastures for 60 to 90 d and supplemented with concentrate at 1.0% of BW. Feeding a high-concentrate diet immediately after EW enhanced the muscle PPARγ expression but did not enhance marbling at slaughter.
authors.affiliation: North Carolina State University, Mountain Research Station, Waynesville 28786.
authors.forename: P
authors.initials: P
authors.lastname: Moriel
authors.affiliation: Virginia Tech University, Department of Animal and Poultry Sciences, Blacksburg 24061.
authors.forename: S E
authors.initials: SE
authors.lastname: Johnson
authors.affiliation: University of Florida - IFAS, Range Cattle Research and Education Center, Ona 33865.
authors.forename: J M B
authors.initials: JM
authors.lastname: Vendramini
authors.affiliation: Virginia Tech University, Department of Animal and Poultry Sciences, Blacksburg 24061.
authors.forename: M A
authors.initials: MA
authors.lastname: McCann
authors.affiliation: Virginia Tech University, Department of Animal and Poultry Sciences, Blacksburg 24061.
authors.forename: D E
authors.initials: DE
authors.lastname: Gerrard
authors.affiliation: University of Florida - IFAS, Range Cattle Research and Education Center, Ona 33865.
authors.forename: V R G
authors.initials: VR
authors.lastname: Mercadante
authors.affiliation: University of Florida - IFAS, Range Cattle Research and Education Center, Ona 33865.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hersom
authors.affiliation: University of Florida - IFAS, Range Cattle Research and Education Center, Ona 33865 jarth@ufl.edu.
authors.forename: J D
authors.initials: JD
authors.lastname: Arthington
mesh_terms: D000375:Aging / Q000502:physiology*; D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D001823:Body Composition / Q000502:physiology*; D002417:Cattle / Q000254:growth & development* / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D005786:Gene Expression Regulation / Q000502:physiology; D006799:Housing, Animal; D008129:Lolium; D008297:Male; D008460:Meat / Q000032:analysis / Q000592:standards; D009124:Muscle Proteins / Q000235:genetics / Q000502:physiology; D031781:Paspalum; D013997:Time Factors; D014886:Weaning; D015430:Weight Gain / Q000502:physiology
chemical_list: D009124:Muscle Proteins
keywords: beef steers; carcass; early weaning; insulin-like growth factor 1; marbling; metabolic imprinting