Production of lean beef containing a high content of trans-10, cis-12 conjugated linoleic acid by feeding a high-temperature-micro-time-treated diet with extruded soybean.

The effects were observed of feeding a high-temperature-micro-time (HTMT)-treated diet of high-quality extruded soybean (ESB) on trans-10, cis-12 conjugated linoleic acid (CLA) incorporation in intra-muscular fat and on the lipid metabolism of twelve Holstein steers. The animals were randomly allocated to three groups, the control group being fed on a normal diet, and the other two groups being fed on a diet containing high-quality ESB with or without the HTMT treatment. The experimental period was four months. The content of total CLA in both the HTMT and non-HTMT-treated diets was higher than that in the control diet (P<0.05). The concentration of trans-10, cis-12 CLA was significantly higher in the HTMT-treated diet than in the non-treated diets at P<0.05, and the HTMT-treatment decreased the intra-muscular fat content (P<0.05). The expression of fatty acid synthase (FAS) and the plasma insulin-like growth factor-1 (IGF-1) level in the HTMT-treated group were lower than those in the control group (P<0.05). Lipoprotein lipase (LPL) mRNA level in the adipose tissue was lower in the non-HTMT-treated group than in the control (P<0.05). These results show that the HTMT treatment increased the level of trans-10, cis-12 CLA in the intra-muscular fat. This increased level of trans-10, cis-12 CLA may inhibit lipogenesis in the intra-muscular fat of Holstein steers.