Effects of pasture and high-concentrate diets on the performance of beef cattle, carcass composition at equal growth rates, and the fatty acid composition of beef

Steen, R.W.J.; Lavery, N.P.; Kilpatrick, D.J.; Porter, M.G.

New Zealand Journal of Agricultural Research 46(2): 69-81

2003


ISSN/ISBN: 0028-8233
DOI: 10.1080/00288233.2003.9513533
Accession: 003743930

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Abstract
Two experiments were carried out to examine the effects of high quality pasture and high-concentrate diets on liveweight and carcass gain of beef cattle, carcass composition at equal carcass gain, and the fatty acid composition of beef. Heifers of late-maturing breed type (406 kg initial liveweight; Experiment 1) and steers of late-maturing breed type (460 kg initial liveweight; Experiment 2) were finished on a ryegrass pasture or a high-concentrate diet at either (1) ad libitum, (2) 85% of ad libitum intake or (3) 70% of ad libitum intake. The high-concentrate diet consisted of 95% barley-based concentrate and 5% barley straw. Carcass gain of the animals finished at pasture (648 g/day) was 0.78 in Experiment 1 (P<0.001) and 0.88 in Experiment 2 (P>0.1) of that of the animals given the high-concentrate diet ad libitum. Gains in lean meat were similar for animals finished at pasture and those given concentrates ad libitum, whereas daily fat gains were 39% lower for the animals finished at pasture (P<0.001). At an equal rate of carcass gain, animals finished at pasture produced carcasses with a higher lean content (P=0.03) and a lower fat content (P=0.03) than those produced from the high-concentrate diet. Muscle from pasture-finished cattle had higher concentrations of omega-3 polyunsaturated fatty acids (PUFA) (141 vs. 49+or-8.2 mg/100 g muscle) and long-chain omega-3 PUFA (58 vs. 27+or-3.8 mg/100 g muscle) than muscle from concentrate-fed cattle. These results highlight the potential of high quality ryegrass pasture for finishing cattle, and meat from pasture-finished cattle as a source of omega-3 PUFA.