URINARY-EXCRETION OF PSEUDOURIDINE AND PURINE METABOLITES IN RUMINANTS

In Experiment 1 yeast ribonucleic acid (RNA) was infused into the duod enum 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 du odenal 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 averag e 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 u rinary excretion of pseudouridine. There were increases in microbial p rotein production and urinary excretion of purine derivatives. In Expe riment 3, urinary excretion of nucleic acid derivatives and body weigh t gain were monitored on growing sheep fed at 0.5 M, 1 M and 2 M. Urin ary excretion of pseudouridine was positively correlated with body wei ght gain. Measurement of pseudouridine from growing and mature non gro wing cattle as well as sheep fed diets that were ad libitum showed tha t 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 ti ssue turnover of nucleic acids.