Influence of level and source of dietary fat on its comparative feeding value in finishing diets for steers: feedlot cattle growth and performance

Two hundred twenty-eight crossbred steers (304 kg) were used in a 125-d comparative slaughter trial to evaluate the influence of level and source of supplemental fats on their feeding value for feedlot cattle. Dietary treatments consisted of a steam-rolled, barley-based finishing diet containing 1) no supplemental fat; 2) 4% yellow grease (YG); 3) 4% blended animal-vegetable fat (BVF); 4) 8% YG; 5) 8% BVF or 6) 6% BVF and 2% crude soybean lecithin. Increasing level of supplemental fat in the diet resulted in linear improvements (P less than .01) in weight gain, feed conversion and NE value of the diet. Estimated NE values of YG and BVF were similar and did not appear to be influenced by level of supplementation, averaging 5.78 and 4.61 Mcal/kg for maintenance and gain, respectively. Fat supplementation resulted in linear increases in empty body fat (P less than .01), kidney, pelvic and heart fat (P less than .01) and marbling score (P less than .05). Partially replacing BVF with lecithin did not influence (P greater than .10) steer performance, carcass merit or estimated NE value of the diet. The comparative feeding value (in terms of both diet acceptability and NE value) of the supplemental fats tested was similar and was apparently not influenced by level of supplementation up to 8% of diet DM.