Processed soybean as a replacement for soybean meal on N retention in milk of Holstein cows

Application of nutritional strategies to reduce dietary crude protein proportion by maintain production performance and/or using protein source with lower degradability in rumen is able to reduce ruminal ammonia N and blood urea N and has positive effect on production and reproduction performance. Accordingly, the objective of this study was to evaluate the effects of soybean processing (roasted soybean and extruded soybean and combination of roasted soybean and extruded soybean) compared with soybean meal on milk yield, NH3N concentration, and milk urea nitrogen concentration in Holstein dairy cows with four multiparous (DIM=113 ± 14) and four primiparous (DIM=96 ± 20) were used in a replicate 4 × 4 Latin square design. Treatments included: 1) 13.88% of diets dry matter (DM) as soybean meal; 2) 15.22% of diet DM as roasted soybean; 3) 15.55% of diet DM as extruded soybean; and 4) 7.69% of diet DM as extruded soybean and 7.69% of diet DM as roasted soybean. N intake was higher in soybean meal treatment than soybean processing. Milk production was similar among treatments (P>0.05). Although parity had no significant effect on percentage of milk protein, but yield of protein (P=0.07) was higher in PP cows than MP cows. Plasma urea N (11.19 vs. 14.90 mg/dl) and milk urea N (10.58 vs. 13.10 mg/dl) reduced significantly in the diets containing processed soybean. Results indicated that replacement of processed soybean for soybean meal did not affect feed net outcome, but decreased plasma urea N and also milk urea N.