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Evaluation of Protective Agents Applied to Soybean Meal and Fed to Cattle I. Laboratory Measurements^{1 ,2,}

Iowa State University of Science and Technology⁴, Ames 50011

Abstract

Soybean meal (SBM) (RN 5—04—604) was treated with three protein-modifying agents such that its microbial degradation in the rumen would be minimized and its postruminal utilization maximized. SBM (44% solvent) was treated with formaldehyde (HCHO) at levels of .2, .4, .6, .8, 1.0 and 1.2% of meal crude protein (CP); heat at temperatures of 127, 138 or 149 C for 4 hr; or a wood molasses product⁵ (Masonex^R) at levels of either 10 or 20%. Measurements of in vitro rumen ammonia accumulations were made at .5-, 2-, 4-, 6-, 8-and 10-hr intervals as predictors of rumen microbial degradation of SBM CP. Effects of modifying agents upon SBM CP solubility were also monitored by water-soluble analysis as predictors of rumen microbial degradation of protein. Rat growth and nitrogen (N) balance trials were used as predictors of postruminal CP utilization of SBM treated with .2, .8 and 1.4% HCHO (Trial I) or 127, 138 or 149 C (Trial II) in 16% protein diets. Rat growth and nitrogen balance on the treated diets were compared with negative control (NC) and positive control (PC) diets without treatment containing 10 and 16% CP, respectively. Results of these laboratory studies predicted that ruminal CP degradation of SBM could be reduced substantially by application of HCHO at minimum levels of approximately .4% of CP and that amounts up to at least .8% could be applied without substantially decreasing postruminal availability. These studies also predicted that heating of SBM at temperatures of 138 up to 149 was needed to minimize rumen degradation without appreciably injuring postruminal availability. Wood molasses was effective at 10 and 20% levels added to SBM in decreasing in vitro rumen ammonia accumulations and decreased CP solubility.

¹ Journal Paper No. J-8973 of the Iowa Agr. and Home Economics Exp. Sta., Ames. Project No. 2140.

² Data from Elvin Thomas' Ph.D. Thesis (1977). Research supported in part by 1SU Research Grants Program and the Masonite Corp., Chicago, IL.

³ Dept. of Animal and Dairy Sciences, Auburn Univ., Auburn, AL 36830.

⁴ Dept. of Animal Science.