The changes in urinary and plasma purine derivatives in response to fasting and level of feeding in llamas were examined. In one experiment, four llamas were gradually deprived of feed within 3 days and then fasted for 6 days. Daily urinary excretion of purine derivatives decreased with feed intake and leveled on the last 3 days of fasting at 177 ± 26 μmol/kg W0.75. Allantoin and uric acid comprised 71% and 15% of total purine derivatives, respectively, in both fed and fasted states, but hypoxanthine plus xanthine increased from 9% to 36%. Plasma concentration of allantoin declined with feed intake reduction, but those of uric acid (217 μmol/l) and hypoxanthine plus xanthine (27 μmol/l) remained relatively unchanged. Concentration of uric acid was higher than that of allantoin, probably due to a high reabsorption of uric acid in renal tubules, which was measured as over 90%. In a second experiment, the four llamas were fed at 860 and 1740 g dry matter/d in a crossover design. Urinary total purine derivatives excretion responded to feed intake (10.4 vs 14.4 mmol/d), although the observed differences did not reach significance. Compared with some ruminant species, it appears that the llama resembles sheep regarding the magnitude of urinary purine derivatives excretion but is unique in maintaining a high concentration of uric acid in plasma, which could be part of the llama's adaptation to their environment.
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