Comparative evaluation of rumen-protected fat, coconut oil and various oilseeds supplemented to fattening bulls - 2. Effects on composition and oxidative stability of adipose tissues

The effects of five different dietary fat supplements on fatty acid composi tion and oxidative stability of subcutaneous and kidney fat were evaluated in 36 Brown Swiss bulls and compared to a low fat diet in a monofactorial d esign. The following fat supplements were provided as additional fat at 30 g per kg feed dry matter: crystalline rumen-protected fat, coconut oil, and three types of crushed whole oilseeds (rapeseed, sunflower seed and linsee d). Adipose tissues reflected differences (P < 0.05) in dietary fatty acid composition although to a lower extent. Using protected fat, which containe d elevated levels of trans fatty acids, and sunflower seed, containing a hi gh proportion of linoleic acid, significantly increased C18:1 trans fatty a cid proportion in the adipose tissues. The use of sunflower seed increased conjugated linoleic acid. The oilseeds resulted in lower amounts of C16:0 i n favour of C18:0. Except for linseed, all fat supplemented groups improved oxidative stability of adipose tissues as compared with control. This was explained by lower proportions of unsaturated fatty acids in adipose tissue (protected fat), by elevated alpha-tocopherol contents (rapeseed, sunflowe r seed) or by a combination of both (coconut oil). Fat colour remained unaf fected by treatments. Compared to other fat supplements oilseeds, especiall y sunflower seed and rapeseed, can therefore be recommended to be fed to bu lls in order to increase the proportions of C18 unsaturated fatty acids in adipose tissues and to maintain or improve oxidative stability.