Abstract Consumption of grazed pasture compared to concentrates results in higher concentrations, in beef muscle, of fatty acids considered to be beneficial to human health. Little information is available on the influence of the type of grazed forage. Our objectives were to determine 1) the effect of inclusion of white clover in a grazing sward on the fatty acid profile of beef muscle and 2) the potential of the fatty acid profile and stable isotope ratios of C and N to discriminate between beef from cattle that grazed grass-only or grass/clover swards before slaughter. A total of 28 spring-born Charolais steers grazed from March until slaughter in October, either on a perennial ryegrass (Lolium perenne L.) sward that received approximately 220 kg N/ha or a perennial ryegrass–white clover (Trifolium repens L.) sward that received 50 kg N/ha. The longissimus muscle from cattle finished on grass/clover had a higher (P < 0.05) proportion of C18:2 and C18:3 but a lower (P < 0.05) proportion of conjugated linoleic acid and δ15N value than animals finished on the grass-only sward. Discriminant analysis using the fatty acid data showed that, after cross-validation, 80.7% of grass/clover and 86.1% of grass-only muscle samples were correctly classified. Discriminant analysis using the stable isotope data showed that, after cross-validation, 95.7% of grass/clover and 86.5% of grass-only muscle samples were correctly classified. Inclusion of white clover in pasture is likely to have little effect on healthiness of meat for consumers. However, changes in fatty acids and stable isotopes can be used to distinguish between grass/clover-fed and grass-only-fed beef.

中文翻译：

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屠宰前放牧草或草/三叶草牧场的牛肌肉的脂肪酸谱和 C 和 N 的稳定同位素比及其鉴别潜力

摘要 与浓缩物相比，食用放牧草会导致牛肉肌肉中更高浓度的脂肪酸被认为对人类健康有益。关于放牧草料类型的影响的信息很少。我们的目标是确定 1) 在放牧草场中加入白三叶草对牛肉肌肉脂肪酸谱的影响，以及 2) 脂肪酸谱和 C 和 N 的稳定同位素比在区分牛肉和牛牛肉方面的潜力在屠宰前只吃草或草/三叶草的草。从 3 月到 10 月，共有 28 头春季出生的夏洛来公牛在接受约 220 千克 N/ha 的多年生黑麦草（Lolium perenne L.）草场或多年生黑麦草白三叶草（Trifolium repens L.）上放牧接收 50 kg N/ha 的草料。与在草地上完成的动物相比，在草/三叶草上完成的牛的最长肌的 C18:2 和 C18:3 比例较高（P < 0.05），但共轭亚油酸和 δ15N 值的比例较低（P < 0.05） -只有草。使用脂肪酸数据的判别分析表明，经过交叉验证，80.7% 的草/三叶草和 86.1% 的纯草肌肉样本被正确分类。使用稳定同位素数据的判别分析表明，经过交叉验证，95.7% 的草/三叶草和 86.5% 的纯草肌肉样本被正确分类。在牧场中加入白三叶草可能对消费者的肉类健康影响不大。然而，脂肪酸和稳定同位素的变化可用于区分草饲/三叶草喂养和仅草饲牛肉。