RESPONSE OF LACTATING DAIRY COWS TO FORMALDEHYDE-TREATED SOYBEAN MEAL WHEN FED WITH CONTROL OR UREA-TREATED CORN SILAGE

In two experiments, lactating cows (26 in exp. 1; 32 in exp. 2) were fed an 11.3% crude protein (CP) diet, a 14.7% CP diet containing untreated soybean meal (SBM) or a 14.6% CP diet containing formaldehyde-treated SBM (FSBM), all three fed as a complete blended diet with control corn silage (CCS) (exp. 1); a 12% CP diet, a 13.4% CP diet containing SBM or a 13.3% CP diet containing FSBM, all fed as a complete blended diet with urea-treated corn silage (UCS) (exp. 2). In both experiments concentrates and CCS or UCS were mixed (50:50 dry matter) daily and fed ad lib for a 16-wk period. The increase of CP over the low CP negative control by addition of untreated SBM resulted in a significant (P < 0.05) increase in milk production in both experiments. The addition of FSBM had no significant effect. When comparing solids-corrected milk (SCM), addition of SBM, whether treated or not, significantly increased SCM in both experiments. In neither experiment did FSBM improve milk production over untreated SBM. All an...