Chen and Gomes (1992) provided a simple approach
to predict microbial N flow from urinary purine derivative
excretion, obviating the need for cannulated
cattle. They described microbial N flow to the duodenum
(g of N/d) as 0.727 × microbial purines absorbed
(mmol/d), where absorption of microbial purines was
calculated as a function of excretion of urinary purine
derivatives and metabolic BW. Predictions of microbial
N flow based on urinary purine derivative excretion and
the equations of Chen and Gomes (1992) led to values
Table 6. Effect of N supplementation on plasma metabolites and urinary clearance
rates in steers consuming corn-based diets supplemented with no protein (control),
distillers dried grains with solubles (DDGS), or urea