Production responses to diets supplemented with soybean meal, expeller soybean meal, or dry-extruded cottonseed cake by lactating dairy cows

Abstract

ABSTRACT Objective The objective of this trial was to evaluate the performance of lactating cows fed diets in which cottonseed cake (CSC) completely replaced either solvent-extracted soybean meal (SBM) or expeller SBM (ESM) to evaluate value of CSC as either source of ruminal degradable or undegradable protein supplement. Materials and Methods Forty-eight mid-lactation Holstein cows were used in a randomized complete block trial with a 3-wk standardization period followed by an 8-wk experimental period. Intake and production were monitored throughout the trial. The CSC was produced by dry extruding whole cottonseed at 121 to 149°C for 12 to 20 s. The resulting CSC contained approximately 33% CP with 45% ruminally degradable protein and 55% ruminally undegradable protein (DM basis). Treatments included (1) control diet supplemented with SBM and ESM (CONT), (2) CSC substituted for SBM (CSRDP), and (3) CSC substituted for ESM (CSRUP). Results and Discussion No differences were observed in DMI; milk yield; ECM yield; or percentage or yield of milk fat, lactose, or solids not-fat among treatments. No differences were observed in yield of milk protein, but milk protein percentage was less for CSRDP compared with CONT but not different from CSRUP. Milk urea nitrogen concentrations were less for CSRDP compared with CONT and CSRUP: 8.56, 7.58, and 9.27 mg/dL for CONT, CSRDP, and CSRUP, respectively. No differences were observed in change of BW or BCS during the trial among treatments. Implications and Applications Results of this trial indicate that the CSC can be substituted for SBM or ESM without affecting intake or milk yield and composition. The lower MUN observed for CSRDP suggests that substituting the CSC for SBM may have limited degradable N.