title: Effects of timing and duration of dietary vitamin A reduction on carcass quality of finishing beef cattle.
abstract: Two feedlot studies were conducted to investigate the timing and duration of supplemental vitamin A withdrawal from feedlot cattle (Bos taurus) diets to reduce intramuscular adipose tissue vitamin A concentration and improve carcass quality. In Exp. 1, Angus crossbred steers (n = 84, BW = 211 ± 4 kg) were allotted to 4 treatments: no supplemental vitamin A for 227 d, no supplemental vitamin A for 112 d followed by 115 d of supplemental vitamin A, supplemental vitamin A for 112 d followed by no supplemental vitamin A for 115 d, or supplemental vitamin A for 227 d. In Exp. 2, Angus crossbred steers (n = 80, BW = 210 ± 5 kg) were allotted to 4 treatments: early weaning with or without supplemental vitamin A, and traditional weaning with or without supplemental vitamin A. In both experiments, serum vitamin A concentrations were greatest (P < 0.05) 56 d after cattle were weaned and placed in the feedlot, regardless of feedlot dietary vitamin A concentration. Hepatic vitamin A stores were dramatically decreased (P < 0.05) in the first 56 d and remained depressed as long as steers were not supplemented with vitamin A. At the end of the finishing period, vitamin A concentrations were less in intramuscular than subcutaneous adipose tissue. Growth was not affected by finishing cattle without supplemental dietary vitamin A (P > 0.10). Dietary vitamin A supplementation did not affect USDA yield grades. However, in Exp. 2, cattle without supplemental vitamin A had greater (P < 0.001) ether extractable lipid in the LM. Ether extractable lipid in the LM or marbling scores were enhanced when intramuscular adipose tissue vitamin A concentration was reduced in response to feeding diets without supplemental vitamin A.
authors.affiliation: Department of Animal Science, North Carolina State University, Raleigh, NC 27695, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Pickworth
authors.forename: S C
authors.initials: SC
authors.lastname: Loerch
authors.forename: F L
authors.initials: FL
authors.lastname: Fluharty
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects / Q000502:physiology; D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition / Q000187:drug effects*; D002338:Carotenoids; D002417:Cattle; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D008055:Lipids; D008297:Male; D014801:Vitamin A / Q000008:administration & dosage / Q000494:pharmacology*; D014815:Vitamins / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D008055:Lipids; D014815:Vitamins; D014801:Vitamin A; D002338:Carotenoids