Abstract
Urinary purine derivatives and creatinine excretion was measured in a total of 4 white Alpine sheep. They were given diets 718 to 1060 g/kg dry matter (DM) of roughage. The crude protein content of this diets was on average $93.87{\pm}5.57g$ in kg DM. Purine derivatives-N excretion increased linearly with incremental DM intake and was significantly correlated (n = 16) with amounts of digestible organic matter (DOM) intake: allantoin-N (mg) = 1.205 (${\pm}0.070$) $\times$ DOM (g) - 136.709 (${\pm}37.399$), r = 0.9770, RSD = 22.97; uricacid-N (mg) = 0.131 (${\pm}0.041$) $\times$ DOM (g) + 11.380 (${\pm}21.881$), r = 0.6306, RSD = 13.44; Hypoxanthine-N (mg) = 0.049 (${\pm}0.014$) $\times$ DOM (g) - 28.640 (${\pm}7.708$), r = 0.6544, RSD = 4.73; total purine derivatives-N (mg) = 1.385 (${\pm}0.083$) $\times$ DOM (g) - 90.261 (${\pm}44.552$), r = 0.9706, RSD = 27.47. Microbial protein synthesis per kg DOM was estimated of 113 g. The urinary creatinine-N excretion was on average 9.10 mg/kg live weight (LW) with a standard error of 0.12 mg creatinine-N per kg LW. The excretion of creatinine excreton was not related to feed intake. Daily creatinine excretion (mg/d) was calculated from individual LW measurements and the average creatinine excretion (mg/kg LW). It was possible to predict the daily urinary purine derivatives excretion (r = 0.9720 for allantoin, r = 0.9886 for total purine derivatives) from the ratio of purine derivatives (mg/100 ml) and creatinine (mg/100 ml) in the urine and the daily creatinine excretion.