EFFECTS OF POST-RUMINAL FERMENTATION ON THE FECAL AND URINARY-EXCRETION OF PURINES

The effect of post-ruminal fermentation on faecal output of purine bas es (PB) and urinary excretion of their derivatives (PD) was studied by the infusion of yeast RNA (2.9 g/day), corn starch (100 g/day), cellu lose (200 g/day) and saline solutions into the gastro-intestinal tract of four sheep (35.4 kg live weight) fitted with caecal and duodenal c atheters and given 0.80 kg/day alfalfa hay. All substrates were infuse d into the caecum except cellulose that was infused into the proximal duodenum. The infusion of RNA did not affect either the faecal excreti on of PB or the urinary excretion of allantoin or total PD, although x anthine excretion increased significantly from <0.01 to 0.12 mmol/day. Starch and cellulose infusions promoted a significant increase in the faecal excretion of diaminopimelic acid (206 and 159 v. 131 mg/day) a nd PB (4.55 and 3.62 v. 2.29 mmol/day) and modified the partitioning o f total nitrogen losses between faeces and urine. The urinary excretio n of allantoin and total PD were not affected by the caecal infusion o f starch (6.60 and 22.9 v. 7.02 and 22.8 mmol/day) but both tended to increase with the duodenal infusion of cellulose (7.75 and 26.4 mmol/d ay). It is concluded that the urinary excretion of PD is independent o f either the supply of nucleic acids to the caecum or the extent of hi nd gut fermentation although it may be affected by variations in the f low of undigested fibre along the small intestine.