Effect of inclusion level of corn germ meal on the digestible and metabolizable energy and evaluation of ileal AA digestibility of corn germ meal fed to growing pigs

Two experiments were conducted to investigate the effect of inclusion level of corn germ meal (CGM) on the DE and ME values of CGM and to evaluate the ileal AA digestibility of CGM fed to growing pigs. In Exp. 1, 42 barrows (63.8 +/- 2.1 kg BW) were allotted to seven diets in a completely randomized design with six replicates per diet. Diets included a corn-soybean meal (SBM) diet and six additional diets containing 4.85%, 9.70%, 19.40%, 29.10%, 38.80%, or 48.50% CGM. Pigs were fed twice daily, at 0730 and 1630 hours, at a level of 4% of BW, and feces and urine were collected for 5 d. The apparent total tract digestibility (ATTD) of DM, OM, CP, acid-hydrolyzed ether extract, and the DE and ME in diets linearly decreased (P < 0.01) as dietary CGM increased. Inclusion level of CGM had no effect on the DE and ME values of CGM. On a DM basis, the concentration of DE and ME varied from 3,396 to 3,747 kcal/kg and 3,107 to 3,502 kcal/kg, respectively. In Exp. 2, 11 crossbred barrows (30.4 +/- 2.9 kg BW) with a T-cannula in the distal ileum were allotted to an 11 x 6 Youden square design with 11 diets and 6 period, which included an N-free diet and 10 CGM test diets. Chromic oxide (0.3%) was included in all diets as an indigestible marker. Pigs were fed daily at 4% of BW during each period, which consisted of 5 d of diet adaptation followed by 2 d of digesta collection. The apparent ileal digestibility (AID) of Ile, Thr, and Ala and the standardized ileal digestibility (SID) of CP and Ile varied (P < 0.01) among the 10 CGM. The AID of CP and all AA except Pro and Tyr, and the SID of all AA except Pro were the greatest (P < 0.05) in sample 7. The AID and SID of CP averaged 40.47% and 64.75%, respectively, and varied from 32.30% to 54.87% and from 57.48% to 72.15%, respectively. The average SID of Lys, Met, Thr, and Trp was 65.61%, 76.15%, 65.29%, and 60.17%, respectively, with a SEM of 4.49, 2.40, 5.95, and 6.82, respectively. The average SID of Pro was 101.76%, with an SEM of 17.26. Increasing dietary CGM decreased the ATTD of nutrients, the DE and ME values of diets but CGM. The AID and SID of AA in CGM are low but source dependent, and CGM may be fed to pigs as an protein-rich feedstuff.