Abstract
In a series of in vitro experiments, some factors influencing the utilization of non-protein nitrogen (NPN) by rumen microorganisms were studied. Media used in this study consisted of 10ml of strained rumen fluid, 30ml of the mineral solution, and various nitrogen and energy sources. The results obtained are summarized below. 1. The amount of microbial protein and deoxyribonucleic acid (DNA) increased with the time of incubation and doubled during 6hr of incubation. The concentration of ammonia had a maximum value at the 1st hour of incubation and then gradually decreased. 2. The rate of incorporation of ammonium sulfate-15N into microbial nucleic acid-N was farster than that into microbial protein-N in the earlier part of the incubation period. 3. No marked differences were found among any of the NPN compounds tested as nitrogen sources except for biuret. Biuret was less (P<0.01) available than other NPN compounds such as urea for the utilization of NPN. 4. Starch was more effective in promoting the utilization of NPN than other energy sources tested such as glucose and cellulose powder. 5. The greatest amount of microbial protein was synthesized when both urea and amino acids were supplied to the medium as nitrogen sources.
