Phosphorus bioavailability, true metabolizable energy, and amino acid digestibilities of high protein corn distillers dried grains and dehydrated corn germ

There is currently much ongoing research and interest for developing new processing technologies to produce corn distillers dried grains with solubles (DDGS). The current study evaluated a high protein (HP) distillers dried grains (DDG) and a dehydrated corn germ, which are products that can be produced by a modified dry milling process. Two chick experiments were conducted to determine the P bioavailability based on tibia ash. In addition, precision-fed rooster assays were conducted to determine TME_n and amino acid digestibility. In the first chick assay, a P-deficient cornstarch-dextrosesoybean meal basal diet containing 0.10 to 0.13% nonphytate P was supplemented with 0.0, 0.05, and 0.10% P from KH₂PO₄ or 7 and 14% conventional DDGS, HP DDG, and corn germ. In the second experiment, the P-deficient basal was supplemented with 7 and 14% conventional DDGS and 12.5 and 25% HPDDG. New Hampshire x Columbian female chicks were fed the experimental diets from 9 to 22 d posthatch, and bioavailability of P was estimated using the slope-ratio method where tibia ash was regressed on P intake. The total P content (90% DM basis) of the conventional DDGS, HP DDG, and corn germ were 0.76, 0.33, and 1.29%, respectively. Bioavailabilities of the P in conventional DDGS, HPDDG, and corn germ relative to KH₂PO₄ were found to be 60, 56, and 25%, respectively. The TME_n in conventional roosters was found to be significantly reduced for HP DDG and increased for the corn germ when compared with the conventional DDGS. The protein content (90% DM basis) of the HP DDG and corn germ was 33 and 14%, respectively, and the total lysine as a % of CP was approximately 2 times greater for the corn germ than for the HP DDG. Amino acid digestibilities in cecectomized roosters were consistently higher for the corn germ than for the HP DDG, which was similar to conventional DDGS.