where Y = recycled nitrogen (Y = 121.7 -12.01X + 0.3235X2; X = IP and is expressed as per cent of DM), RDPA = rumen degraded protein, NPN = non-protein nitrogen derived from the diet, PEPUPNR = peptide nitrogen retained by microbes, NSCAMMNR = ammonia nitrogen retained by NSCBact, and SCAMMNR = ammonia nitrogen retained by SCBact.
Bacterial nitrogen is algebraically divided into true protein, cell wall-associated nitrogen, and nucleic acid nitrogen. These various nitrogenous fractions and fractions derived directly from feed leave the rumen and are digested and absorbed as separate entities allowing specification of unique digestion coefficients for each pool of nitrogen.
This approach overcomes a number of deficiencies inherent in the NRC model. These include linkage of microbial yields, rates of particle and fluid passage, and chemical composition of diets; division of microbial populations by substrate; allowance for variance in ruminal and postruminal digestion of nitrogenous components due to changes in rates of particle passage; and estimates of rumen ammonia concentration.
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