Determination, comparison, and prediction of digestible energy, metabolizable energy, and standardized ileal digestibility of amino acids in novel maize co-products and conventional distillers dried grains with solubles for swine

The objectives of this study were to determine and compare the digestible energy (DE), metabolizable energy (ME), and the coefficient of standardized ileal digestibility (CSID) of amino acids (AA) in novel maize co-products and distillers dried grains with solubles (DDGS) for swine and to compare in vivo determined values with calculated values from published equations. Seven maize co-products were used including two sources of conventional DDGS (DDGS-A and DDGS-B), two sources of high protein distillers dried grains (HPDDG-A and HPDDG-B), two sources of high yeast and protein co-products (HYP-A and HYP-B), and one source of maize fiber and solubles (MFS). In Exp. 1, thirty-two barrows (initial body weight = 24.2 ± 3.4 kg) were housed individually in metabolism crates and randomly allotted to a maize-soybean meal basal diet or 1 of 7 diets, in which 300 g/kg of each co-product partially replaced a portion of maize and soybean meal, in a randomized two-period crossover design. Feces and urine were collected in two 7-d adaptation and 4-d collection periods. In Exp.2, sixteen ileal-cannulated barrows (initial body weight = 37.0 ± 3.8 kg) were housed in metabolism crates and assigned to a nitrogen-free diet or 1 of 7 diets containing 300 g/kg of each maize co-product as the sole crude protein (CP) source in a repeated 8 × 4 Youden square design to determine CSID of AA. Diets were fed for four consecutive 7-d periods (5-d adaptation and 2-d ileal digesta collection). Co-products contained 18.34–22.28 MJ/kg gross energy, 155.3–502.0 g/kg CP, 46.2–137.4 g/kg ether extract, 95.2–463.2 g/kg neutral detergent fiber, and 4.3–20.8 g/kg Lys on an as-fed basis. The HYP-A and HYP-B had the greatest DE (18.04 and 17.51 MJ/kg DM, respectively) and ME (17.24 and 16.63 MJ/kg DM, respectively) compared with other co-products (P < 0.05), and HPDDG-B had the lowest (P < 0.05) DE and ME. The CSID of Lys ranged from 0.30 to 0.70 among co-products. The CSID for Arg, His, Ile, Lys, Met, Thr, and Val were not different among DDGS-B, HPDDG-A, HYP-A, and HYP-B, while HPDDG-B had the lowest (P < 0.05) CSID for all AA. Use of published equations for DDGS resulted in low prediction accuracy and precision for estimating DE, ME, and SID AA compared with observed values. The high ME and SID Lys, Met, Thr, and Trp of HYP-A and HYP-B indicated greater feeding value for swine compared to other co-products evaluated.