The nutritive value of rumen micro-organisms in ruminants. 2. The apparent digestibility and net utilization of microbial N for growing lambs.
Four experiments were conducted with eighteen lambs sustained entirely by intragastric nutrition at gross energy inputs varying from 430 to 860 kJ/kg live weight0.75 (W0.75). Isolated rumen micro-organisms (RMO) were infused into the abomasum in quantities varying from 0 to 2 g digestible N/kg W0.75 to assess the increase in N balance as a result of increasing RMO input when N was limiting. The over-all utilization of N from RMO (RMO-N) could be described by the equation y = 0.543 X -0.457, residual SD = 0.037, where y is the N balance and X is the abomasal input of RMO-N, both expressed in g/kg W0.75. Thus the coefficient of efficiency of utilization of infused RMO-N was 0.543 (SE 0.008). The coefficient of efficiency of utilization of RMO-N truly digested (i.e. the biological value) was 0.659 (SE 0.015). The RMO-N input (mean with SE) at N equilibrium was 0.843 (0.009) g/kg W0.75. The true digestibility of RMO-N was 0.813 (0.004). The urinary N excretion when no N was infused was 0.329 (0.008) g/kg W0.75 and the N excreted via the faeces with zero N input was 0.036 (0.009) g/kg W0.75.
D000596:Amino Acids / Q000378:metabolism; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001419:Bacteria / Q000378:metabolism; D004063:Digestion; D005260:Female; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D009753:Nutritive Value; D012417:Rumen / Q000382:microbiology*; D012756:Sheep / Q000378:metabolism*
D000596:Amino Acids; D009584:Nitrogen