PSIV-1 Effect of Corn Silage Inclusion Rate on Apparent Total Tract Digestibility of Dry Matter, Organic Matter, and Crude Protein in Finishing Steers
Abstract Maine-Anjou × Angus beef steers (n = 156; initial BW 366 ± 37.2 kg) were used in a finishing experiment at the Ruminant Nutrition Center in Brookings, SD. Steers were weighed on 2 consecutive days and assigned into 5 weight blocks. Treatments were arranged in a 2 × 2 factorial, 2 types of implants and 2 dietary treatments with 5 replicate pens for each simple effect. Dietary treatments consisted (DM basis) of 1) 15% (CS15) or 2) 30% corn silage (CS30). Other ingredients consisted of a 50:50 blend of DRC and HMC, liquid supplement and a dry supplement. Bunks were managed using a slick bunk approach and all diets contained (DM basis) 33 mg/kg monensin sodium. Feed collections occurred during the morning and afternoon feedings for two days prior to fecal collections. Each feed sample was composited in equal amounts to create a single sample for each pen. Two fecal collections from each steer occurred 7 hours apart on day 112 of the study. Feces from each steer were composited in equal amounts to create a pen sample. All samples were dried and ground through a 1-mm screen. Acid insoluble ash was used as an internal marker. Apparent total tract digestibility was calculated using the equation: 100-100 ˣ (feed marker/fecal marker) × (fecal variable/feed variable). No interaction between implant and diet was detected for any variables (P ≥ 0.08). One pen was removed from the statistical analysis due to all values being 3 standard deviations away from the mean. Intake did not differ between CS15 and CS30 (P = 0.41). Fecal output was increased 36.9% (P = 0.01) in CS30. Dry matter, organic matter, and crude protein digestion were decreased by feeding CS30 (11.47%, 10.83%, 16.35% respectively; P ≤ 0.03). As corn silage inclusion increases, digestibility coefficients for DM, OM, and CP are decreased.