169 Increasing levels of sorghum dried distillers grains with solubles in feedlot diets: effects on nutrient digestibility ruminal degradability and fermentation

摘要

The objective of this study was to determine the effect of increasing levels of sorghum dry distillers grains with solubles (DDGS) in high concentrate feedlot diets in the nutrient digestibility (%), ruminal degradability (%), pH, NH4 (µg N-NH4/ml) and volatile fatty acid (VFA, mM/l) concentration. Four ruminally cannulated steers (450 ± 63 kg) were used in a 4x4 Latin square design, evaluating four treatments in four periods of 19 days each, with 14 days of adaptation and 5 days of measurements. Animals received a TMR, 92% concentrate (63% sorghum grain, 25% soybean meal, 4% mineral commercial premix), with DDGS (90% DM, 29% CP, 51% NDF, 9% EE) in increasing levels generating 4 treatments: 0, 15, 30, or 45%. Replacing a combination of sorghum grain and soybean meal to maintain diets isoproteic. The TMR was offered ad-libitum to each animal in individual pens. Greater levels of DDGS increased the consumption of NDF (P = 0.0001) and EE (P = 0.0004), and NDF total tract apparent digestibility (linear; P = 0.038), but it decreased quadratically EE total tract apparent digestibility (P = 0.017). The DM (84.2 ± 0.17) and the CP total tract apparent digestibility (85.3 ± 2.0) was not affected by increasing levels of DDGS. Nevertheless, the ruminal degradability of total DM (P = 0.01) and CP decreased linearly (P = 0.01), without affecting NDF degradability (65.6 ± 4.3). Increasing levels of DDGS did not change ruminal pH (5.6 ± 0.14), acetate (45.1 ± 6.3), propionate (24.8 ± 3.6), and butyrate (5.2 ± 0.7) concentration, but NH4 concentration decreased linearly (P < 0.0001) directly related to the decreased CP ruminal degradability. Increasing levels of DDGS inclusion in a high concentrate diet reduce the CP ruminal degradability, without changes in total CP digestibility, what indicates a change of the site of digestion.