Abstract

Twelve 24-month-old crossbred beef cattle with initial live weight of 532.6±20.9 kg were used to study the effect of feeding different levels of roasted soybeans on conjugated linoleic acid (CLA) and other fatty acids of longissimus dorsi muscle, subcutaneous fat and liver. The cattle were randomly divided into three groups with 4 cattle in each group and were fed rations containing 3.6, 10.1 and 15.7% of roasted soybeans as Treatments I, II and III, respectively. The cattle were slaughtered after feeding for 28 days and the samples of longissimus dorsi muscle, subcutaneous fat and liver were obtained. The fatty acid composition of the samples was analysed and statistically compared. In longissimus dorsi muscle, it was found that c9t11-CLA content was significantly increased with soybean level (P<0.01) whereas contents of C18:0, C18:1, C18:2n-6, C18:3, t10c12-CLA and total CLA were unchanged (P>0.05). In subcutaneous fat, both c9t11-CLA (P=0.056) and total CLA (P = 0.067) tended to increase with soybean level while all other fatty acids were unchanged (P > 0.05). In liver, content of C18:1 was significantly decreased while contents of C18:2n-6 and C18:3 were significantly increased with soybean level (P < 0.01). Significant correlations were found between intake and contents of fatty acids C18:0, C18:1, C18:2n-6 and C18:3 in liver. This study concludes that feeding beef cattle with soybeans up to 15.7% in high forage-based ration is not an effective way to increase total CLA content of tissues.

Key words: Soybeans, conjugated linoleic acid, longissimus dorsi muscle, subcutaneous fat, liver, beef cattle.