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

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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 −1 ) 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 versus 49 ± 8.2 mg 100 g −1 muscle) and long‐chain omega‐3 PUFA (58 versus 27 ± 3.8 mg 100 g −1 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.

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