Symposium on Concentrated Animal Feeding Operations Regarding Animal Behavior , Care , and Well Being 848

resulted in improved ileal true digestibility (TD) of protein. Petroleum spirit-extracted dehulled soybean (TI 58.4 mg/g DM) was adjusted to 780 g/kg DM and heated alone or with either sodium metabisulphite (11.8 g/kg DM) or cysteine (15 g/kg DM) for 25, 35, 55 or 75 minutes at 95C. Reactive SH, determined by reaction with 4-vinyl pyridine and HPLC separation, was increased by C and S and decreased with heating time. Heating decreased TI 3.9 times faster in the presence of S but not of C. Each of these 12 preparations was included as the sole source of protein in diets formulated for chicks to provide 150, 200 or 250 g CP/kg diet. A diet with enzyme hydrolysed casein plus amino acids (E) as the sole source of protein at 200 g CP/kg diet was used to measure endogenous loss. Chromic oxide was the marker. The diets were offered to 3 cages of 3 chicks (E to 9 cages) ad libitum for 3 days (8 to 10 d of age). Food was removed overnight on day 10 and each cage was fed at timed intervals ad libitum on day 11 for 4 hours before euthanasia with pentobarbitone sodium given intra peritoneum. TD was calculated as 1-slope of the regression of ileal N per g diet on diet N per g diet using diet E as a zero test dietary N level together with the 3 levels of each test material. TD (mean SEM) soybean alone 0.670.029, 0.780.037, 0.790.026, 0.870.009; +C 0.720.028, 0.860.023, 0.870.014, 0.860.018; +S 0.880.021, 0.890.014, 0.890.013, 0.880.010 at 25, 35, 55, 75 minutes respectively. TD of soybean alone increased with heating time to 75 minutes. The same maximum TD was achieved in 35 minutes with added C and in 25 minutes with added S. The TD achieved with added S was slightly but not significantly greater than the maximum achieved on heating soybean alone (difference 0.0250.0160, t 1.56).