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Degradation of Feedstuff Nitrogen in the Rumen vs Nitrogen Solubility in Three Solvents

University of Maine², Orono 04473

Abstract

Dacron bags, each containing a .5 g sample of one of 28 feedstuffs, were placed in the rumen of a fistulated steer. Disappearance of nitrogen compounds was determined at intervals for 6-hr to determine the relative rates of ruminal protein degradation. The nitrogen (N) disappearance after 2-hr rumen exposure was correlated with the quantities of N solubilized by 1-hr extractions of the same feeds using 10% Wise Burroughs Mineral Buffer (WB), .15 molar sodium chloride (NaCl) or autoclaved rumen fluid (ARF). The overall correlation coefficients for the 2-hr degradations of all feeds with WB, NaCl and ARF were .66, .47 and .54, respectively. The correlations between the 2-hr ruminal degradations and the WB solvent were improved by dividing the feeds into the categories of concentrates, hays and silages. A lower correlation for hays than for silages or concentrates was noted, and further comparisons of the solubility of hay protein in WB with the ruminal degradations at various intervals revealed a higher correlation after 4-hr of rumen exposure. Correlations for rumen degradation at 2-hr for concentrates and silages, and at 4-hr for hays with the solubility in WB were .70, .94 and .88, respectively.

¹ Present address: Animal Sciences Department, Cornell University, Ithaca, NY 14853.

² Department of Animal and Veterinary Sciences.