Conjugated linoleic acid content of beef from cattle fed diets containing high grain, CLA or forages

Twenty Angus crossbred steers were assigned to one of four treatments and followed from weaning to slaughter to study the effect of diet on the conjugated linoleic acid (C18:2 cis-9, trans-11 and C18:2 trans-10, cis-12 CLA isomers) content and quality of beef. During the adaptation period, treatments 1 (CTL), 2 (CLA), and 3 (GPS) received a diet consisting of 520 g corn silage, 213 g alfalfa hay, 250 g rolled barley, and 17 g mineral–vitamin premix/kg of dry matter (DM). Treatment 4 (PS) received alfalfa hay only. During the finishing period, CTL and CLA steers received a diet consisting of 123 g corn silage, 67 g alfalfa hay, 764 g rolled barley, and 46 g mineral–vitamin premix/kg of diet dry matter. In addition to the basal diet, CLA steers received 84 g/head/day of a synthetic mixture of partially rumen protected CLA isomers. The GPS and PS treatments were finished solely on pasture. Subcutaneous adipose tissue samples were collected from the M. longissimus dorsi at the end of the adaptation period, and both adipose and muscle tissues were collected from the longissimus and M. semitendinosus of each carcass at slaughter for fatty acid analysis. Beef tissues from PS and GPS steers had 466% and 218% more CLA (C18:2 cis-9, trans-11 isomer) at slaughter compared with beef tissues from CTL steers, respectively. Supplementing synthetic CLA did not increase C18:2 cis-9, trans-11 CLA content of beef, but increased trans-10, cis-12 CLA by 380% compare to beef from CTL animals. A trained taste panel detected no differences in tenderness or juiciness among treatments. However, beef from PS received higher off-flavor scores than other treatments. Raising cattle on forage and pasture with no grain supplementation enhances beef CLA content. Additionally, finishing cattle on pasture increased the vitamin E content of beef by 300% compared to beef from animals finished on a traditional high-grain diet