Energy, phosphorus, and amino acid digestibility of high-protein distillers dried grains and corn germ fed to growing pigs

Three experiments were conducted to measure energy, P, and AA digestibility in 2 novel coproducts from the ethanol industry [i.e., high-protein distillers dried grains (HP DDG) and corn germ]. These products are produced by dehulling and degerming corn before it enters the fermentation process. Experiment 1 was an energy balance experiment conducted to measure DE and ME in HP DDG, corn germ, and corn. Six growing pigs (initial BW, 48.9 +/- 1.99 kg) were placed in metabolism cages and fed diets based on corn, corn and HP DDG, or corn and corn germ. Pigs were allotted to a replicated, 3 x 3 Latin square design. The DE and ME in corn (4,056 and 3,972 kcal/kg of DM, respectively) did not differ from the DE and ME in corn germ (3,979 and 3,866 kcal/kg of DM, respectively). However, HP DDG contained more (P < 0.05) energy (4,763 kcal of DE/kg of DM and 4,476 kcal of ME/kg of DM) than corn or corn germ. Experiment 2 was conducted to measure apparent total tract digestibility (ATTD) and true total tract digestibility of P in HP DDG and corn germ. Thirty growing pigs (initial BW, 33.2 +/- 7.18 kg) were placed in metabolism cages and fed a diet based on HP DDG or corn germ. A P-free diet was used to measure endogenous P losses. Pigs were assigned to treatments in a randomized complete block design, with 10 replications per treatment. The ATTD and the retention of P were calculated for the diets containing HP DDG and corn germ, and the endogenous loss of P was estimated from pigs fed the P-free diet. The ATTD was lower (P < 0.05) in corn germ (28.6%) than in the HP DDG (59.6%). The retention of P was also lower (P < 0.05) in pigs fed corn germ (26.7%) than in pigs fed HP DDG (58.9%). The endogenous loss of P was estimated to be 211 +/- 39 mg per kg of DMI. The true total tract digestibility of P for HP DDG and corn germ was calculated to be 69.3 and 33.7%, respectively. In Exp. 3, apparent ileal digestibility and standardized ileal digestibility values of CP and AA in HP DDG and corn germ were measured using 6 growing pigs (initial BW, 78.2 +/- 11.4 kg) allotted to a replicated, 3 x 3 Latin square design. The apparent ileal digestibility for CP and all AA except Arg and Pro, and the standardized ileal digestibility for CP and all AA except Arg, Lys, Gly, and Pro were greater (P < 0.05) in HP DDG than in corn germ. It was concluded that HP DDG has a greater digestibility of energy, P, and most AA than corn germ.