Influence of Method Supplementation of Yellow Grease on Growth Performance, Dietary Energetics, Carcass Characteristics and Nutrient Digestion of Feedlot Steers

Two experiments were conducted in order to evaluate two methods of yellow grease (YG) supplementation (5% on a dry matter basis in replaced to the steam-flaked corn in control diet) on cattle growth performance, dietary energetic and site and extent of nutrients digestion. Supplemental methods were as follows: 1) YG added directly on grain (YG was first mixed with the steam-flaked corn in the proportion 50 kg YG to 750 kg corn, prior to adding other dietary ingredients), or 2) YG added on ration (added to the mixer as the next to the last step, prior to adding molasses). A group without YG supplementation was included as controls. Growth-performance trial lasted 151 days (72 crossbred cattle, 273 +/- 0.8 kg LW). Method of YG supplementation did not affect growth-performance, dietary energetics or carcass characteristics. Addition of 5% YG in diets increased (P <= 0.04) feed efficiency (4.7%) and dietary net energy (NE, 5.7%). Based on performance data, the estimated NEm value of YG was 4.38 Mcal/kg. In trial 2, six Holstein steers (313 +/- 5.5 kg) with cannulas in the rumen and proximal duodenum were used in a replicated 3 x 3 latin square design experiment to evaluate treatment effects on digestive function and ruminal fermentation. Yellow grease added directly to the grain decreased (2.6%, P<0.05) postruminal digestion of N without effected the site and extent of digestion of organic matter (OM), starch and fiber. Supplemental YG did not affect ruminal proportion of volatile fatty acids nor ruminal pH, but decreased (P <= 0.04) ruminal digestion of OM (10.4%) and acid detergent fiber (ADF, 36.7%). Supplemental YG tended (P=0.06) to decreased total tract digestion of OM (1.8%) and ADF (13.9%). It is concluded that there are no positive associative effects of adding YG directly to steam-flaked corn on growth-performance or digestive function.