Evaluation of Protective Agents Applied to Soybean Meal and Fed to Cattle II. Feedlot Trials

Abstract

Soybean meal (SBM), 5—04—604, was treated with formaldehyde (HCHO), wood molasses5 (WM) or subjected to heat before incorporation into selected cattle diets for purposes of evaluating treatment agents used in protecting proteins against rumen fermentation degradation. Cattle with initial body weights (BW) averaging 172 to 216 kg were full-fed during four feeding trials. A negative control (NC) high-ground corncob (1—02—782) diet containing untreated SBM and urea was compared with a treated SBM and urea diet whose composition was similar except for the treatment applied. These diets in three of four trials were compared with a positive control (PC) diet containing three times as much untreated SBM and no urea. All diets in a given feeding trial were isonitrogenous and isocaloric. The metabolizable protein (MP) feeding standard was utilized in estimating that each NC diet would be deficient at the beginning of the trial and each PC diet would be adequate in MP with treatment diets supplying intermediate quantities of MP depending upon the effectiveness of the treatment applied. Four levels of HCHO were tested in Trial I. The lowest level most responsive to treatment was .8% of SBM protein. The cattle receiving this level gained 35% more rapidly and converted their feed to gain 22% more efficiently than the NC cattle receiving untreated SBM. In Trials II and III, the WM treatment increased BW gain an average 36% and improved feed conversion an average 24% over the NC cattle. The comparative values for the cattle receiving heat-treated SBM were 50% faster BW gains and 23% more efficient feed conversion over the untreated meal. These same two treatments in Trial IV, in which a corn silage diet was fed containing a higher level of natural protein, resulted in smaller benefits. The positive cattle results obtained with each of the three treatment agents demonstrated the validity and usefulness of these treatment agents on SBM when fed in cattle diets deficient in MP. It was estimated from the feeding trials that each treatment agent protected approximately 50% of the SBM protein against rumen fermentation degradation as compared with only 25% escaping degradation in the untreated SBM. These results also demonstrated the usefulness of the MP feeding system in formulating cattle diets suitable for testing the effectiveness of different protective agents against protein degradation within the rumen.