Effect of levels and kinds of nitrogen and energy sources on the utilization of non-protein nitrogen compounds by rumen microorganisms in vitro

Takahashi, F.; Kametaka, M.; Kandatsu, M.

Japanese Journal of Zootechnical Science 45(3): 157-164


Accession: 000072238

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Rumen fluid, withdrawn from a sheep fed on a commercial dairy cow diet and lucerne hay cubes (3:2), was strained and incubated under CO2 with additions of a mineral mixture, a source of N and maize starch, for several hours, after which the microbial protein formed was estimated. Whem the N source was urea, increasing amounts of it resulted in increased protein synthesis but decreased proportional utilization of urea. During incubation, microbial protein and DNA content increased in parallel, while NH3 content of the medium rapidly increased and then decreased. With ammonium sulphate-15N, more radioactive N was converted into DNA than into protein. Urea and ammonium acetate, sulphate, bicarbonate and succinate were all suitable as N sources but biuret was less so. Protein synthesis was greater with maize starch as energy source than with glucose, and rice starch also was effective. In experiments with an amino acid mixture of proportions similar to those found in the rumen without or with urea, maximum microbial protein synthesis was obtained after incubation for 8 h with amino acid and urea N in the proportion 1:3.