Effects of vitamin A on growth performance and carcass quality in steers Z.A. Kruk a,e, ⁎ , C.D.K. Bottema a,e , J.J. Davis b,e , B.D. Siebert a,e , G.S. Harper c,e , J. Di d,e , W.S. Pitchford a,e a Livestock Systems Alliance, The University of Adelaide, Roseworthy SA 5371, Australia b Victorian Department of Primary Industries, Rutherglen, Vic 3685, Australia c CSIRO Livestock Industries, Queensland Bioscience Precinct, Brisbane, Qld 4067, Australia d Xin Jiang Academy of Animal Science, Urumqi, Xin Jiang 830000, PR China e Cooperative Research Centre for Cattle and Beef Quality, Australia Received 15 July 2006; received in revised form 3 February 2008; accepted 14 February 2008 Abstract Vitamin A plays a critical role in many essential life processes. In herbivores, it is either derived from plant β-carotene or directly as a dietary supplement. In cattle, vitamin A has the potential to influence various carcass traits that are sought by specific beef markets. A group of 20 Angus steers was removed from pasture and fed a low β-carotene and vitamin A cereal-based ration on a feedlot for 308 days. Ten of the steers were supplemented with vitamin A (retinyl palmitate, 60 IU of vitamin A/100 kg body weight/day) and the other ten received no supplement. The results demonstrated that restriction of vitamin A intake changed intramuscular fat deposition without changing subcutaneous fat depots. Angus steers that had been depleted of vitamin A showed increased intramuscular fat in the longissimus thoracis et lumborum (LTL) by 35% (P b 0.026) and seam fat area at the quartering site by 33% (P b 0.0273), when compared with cattle supplemented with vitamin A. There were no changes in intramuscular fat in the semitendinosus. Visually assessed marbling scores were also higher (19%; P b 0.094) in the non-supplemented, depleted group. There was no effect of vitamin A depletion on cattle growth and other meat traits (eye muscle area, meat colour, pH, meat cut weight), meat eating attributes (tenderness, cooking loss) or muscle fibre diameter. The only difference (P b 0.0177) among the meat traits was fat colour where depleted animals had whiter fat than the controls. Moreover, the fat from the vitamin A depleted group was softer with a lower melting point. We conclude that the reduced vitamin A consumption, leading to vitamin A depletion, increases intramuscular fat. On the other hand, the vitamin A depletion did not increase subcutaneous fat depth or change other meat quality traits, suggesting that marbling and these other traits are not invariably related. © 2008 Elsevier B.V. All rights reserved. Keywords: Beef cattle; Marbling; Carcass quality; Vitamin A; Retinol 1. Introduction In order to obtain satisfactory performance of cattle in feedlots when targeting specific markets, it is nec- essary to provide a balanced diet with sufficient essen- tial nutrients. The majority of cattle in feedlots are fed Available online at www.sciencedirect.com Livestock Science 119 (2008) 12 – 21 ⁎ Corresponding author. Livestock Systems Alliance, The University of Adelaide, Roseworthy SA 5371, Australia. Tel.: +61 8 83037640; fax: +61 8 83037689. E-mail address: zbigniew.kruk@adelaide.edu.au (Z.A. Kruk). www.elsevier.com/locate/livsci 1871-1413/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2008.02.008