URINARY-EXCRETION OF PSEUDOURIDINE AND PURINE METABOLITES IN RUMINANTS

In Experiment 1 yeast ribonucleic acid (RNA) was infused into the duodenum of three dry cows for two days at 0 (control), 30, 50 and 70 g d-1. Urinary excretion of pseudouridine in cows was not influenced by duodenal infusion of RNA (19.80, 20.63, 20.32, 19.71 mumol kg W0.75 d-1, for control and 30, 50 and 70 g d-1 of RNA, respectively). The average recovery of duodenally infused purines in urine amounted to 87%. In Experiment 2, cows fed levels of feed intake 1 maintenance (M) and 1.5 M showed no significant difference (P < 0.05) in body weight and in urinary excretion of pseudouridine. There were increases in microbial protein production and urinary excretion of purine derivatives. In Experiment 3, urinary excretion of nucleic acid derivatives and body weight gain were monitored on growing sheep fed at 0.5 M, 1 M and 2 M. Urinary excretion of pseudouridine was positively correlated with body weight gain. Measurement of pseudouridine from growing and mature non growing cattle as well as sheep fed diets that were ad libitum showed that urinary excretion of pseudouridine was highest in young animals (32.8 mumol kg W0.75 d-1) and declined in adults (20.4 mu mol kg W0.75 d-1). It was concluded that pseudouridine in ruminants originates from tissue turnover of nucleic acids.