Hydrolysis time as a factor affecting the nutritive value of feather meal and feather meal-blood meal combinations for growing calves.

The objectives of this research were to determine 1) the effects of hydrolysis time on feather meal (FTH) protein digestion and ruminal escape and 2) whether adding blood meal (BM) to FTH evoked a complementary response in animal performance. A lamb digestion trial was conducted to estimate true protein digestibility of soybean meal (SBM), BM, and FTH hydrolyzed for 10, 12, 15, or 18 min. Ruminal escape was estimated in situ. Two 94-d growth trials were conducted using 60 growing calves (226 kg) per trial to evaluate urea, FTH, BM, and 87.5:12.5, 75:25, and 50:50 combinations (CP percentage basis) of FTH:BM. There were small numerical differences in estimated escape of protein from the rumen and DM and protein digestibilities due to hydrolysis time. True protein digestibility of the 10- and 18-min samples was 5% higher (P less than .05) than for the 12- or 15-min FTH samples. In the growth trial, the slope-ratio technique showed that the most efficiently used protein supplement was 100% BM (protein efficiency = 2.45 +/- .19). No differences (P = .30) in protein efficiency were observed among supplements containing various combinations of FTH:BM. There was a quadratic (P less than .01) response to the level of BM, indicating a complementary effect. The largest complementary effect occurred at the 12.5% level of the BM addition. There were no nutritionally important effects of hydrolysis time between 10 and 18 min. Furthermore, supplements can be formulated more economically using small amounts of BM with FTH without compromising biological efficiency.