Fatty Acid Composition and Eating Quality of Muscle from Steers Offered Grazed Grass, Grass Silage or Concentrate-Based Diets

Abstract

The effects of grazed grass, grass silage or concentrates on the eating quality and fatty acid composition of intra-muscular fat of steers fed to achieve similar carcass growth rates were investigated. Fifty steers were assigned to one of five dietary treatments. The experimental rations offered daily for 85 days pre-slaughter were (a) grass silage plus 4 kg concentrate, (b) 8 kg concentrate plus 1 kg hay, (c) 6 kg grazed grass dry matter (DM) plus 5 kg concentrate, (d) 12 kg grazed grass DM plus 2.5 kg concentrate or (e) 22 kg grazed grass DM. Decreasing the proportion of concentrate in the diet, which effectively increased grass intake, caused a linear decrease in the concentration of intra-muscular saturated fatty acids (SFA) (P \u3c .01) and in the n-6 to n-3 poly-unsaturated fatty acids (PUFA )ratio (P\u3c .001) and a linear increase in the PUFA to SFA ratio (P \u3c .01) and the conjugated linoleic acid concentration (P \u3c .001). There was an interaction (p\u3c 0.05) between ageing time and treatment with treatment d having higher (p\u3c 0.05) tenderness, texture and acceptability values after 2 days ageing, but not after 7 or 14 days ageing. The data indicate that intramuscular fatty acid composition of beef can be improved from a human health perspective by inclusion of grass in the diet without any negative effect on the eating quality

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