Soybean meal (SBM) protected from degradation in the rumen by NaOH, fresh blood (BL) or fish hydrolysate (FH) was evaluated in a digestibility and nitrogen (N) balance trial using weaned male Holstein calves and in a lactation trial (FH was not included) with multiparous high-yielding Holstein cows. N digestibility increased (P < 0.05) by inclusion of NaOH-treated SBM in the diet. N retention by calves increased (P < 0.05) with NaOH or BL treatment. DM intakes and milk composition in the lactation trial were not different across treatments. Milk yield, fat-corrected milk and solids-corrected milk yields and efficiency of protein utilization by cows fed NaOH-treated SBM diet were higher (P < 0.05) than by cows fed untreated SBM diet. These observations suggest that inclusion of NaOH- or BL-treated SBM results in improved protein utilization by young growing calves. NaOH treatment of SBM also results in production of more milk in high-yielding cows during early lactation. Key words: Soybean meal, sodium hydroxide, blood, fish hydrolysate, protected protein, calves, dairy cows
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