Urinary Purine Derivatives Excretion as a Method for Estimation of Rumen Microbial Protein Production in Swamp Buffaloes and Zebu Cattle

Prediction equations based on urinary purine derivatives (PD) excretion rate as an index to predict rumen microbial protein production have been developed for European cattle and sheep. However, there is evidence to suggest that those equations may not be applicable directly to tropical swamp buffaloes (Bubalus bubalis) and zebu cattle (Bos indicus). To establish similar equations for the above two species of ruminant, five studies were conducted. In the first study, endogenous PD excretion rate determined by fasting procedure for swamp buffaloes and the Malaysian indegenous KK. cattle (zebu cattle) were 199 and 300 Ilmol/kgO.75 /day, respectively. Urinary PD excretion rate per kg digestible organic matter intake (DOMI) for buffaloes (8.19 mmol/kg DOMI) was significantly lower than that for KK. cattle (15.45 mmol/kg DOMI). The second study examined the relationship between daily urinary PD excretion (Y, mmol) and exogenous purine bases (PB) supply via duodenal infusion (X, mmol/day). The relationship obtained were Y = O. I 2X+ 12.78 (r2= 0.45) for buffaloes and Y = 0.85X + 7.15 (r2= 0.62) for KK. cattle, suggesting that 12% and 85% of the supplied exogenous purine were excreted in the urine of buffaloes and zebu cattle, respectively. In the third study, labelled [8_14C] uric acid marker was used to test the hypothesis that the lower recovery rate of urinary PD in swamp buffaloes was due to their higher recycling of plasma PD as compared to KK cattle. The averaged non-renal PD loss of plasma PD for swamp buffaloes and KK cattle did not differ significantly

Renal and salivary excretions of plasma purine derivatives in swamp buffaloes and zebu cattle

This study compared the recovery rate of intrajugular-administered allantoin in the urine and saliva between swamp buffaloes and zebu cattle to examine whether it could explain the lower excretion rate of urinary purine derivatives (PD) in the buffaloes. Three male swamp buffalo yearlings, with an average body weight of 349±40.35 kg, and three Thai native cattle (154±3.26 kg) of similar age and sex were used in the study. Animals were kept in individual pens and fed at a maintenance energy level with a diet containing 65% monk bean husk (Vigna radiata) as roughage and 35% concentrates. Allantoin solution was infused into the jugular vein in four incremental rates equivalent to 0, 5, 10 and 15 mmol/d and urine was collected daily in acidified form. Daily PD excretion was linearly correlated with intrajugular allantoin infusion in both species. The relationship between daily urinary PD excretion (Y, mmol/d) and intrajugular allantoin infused (X, mmol/d) was Y = 0.75±0.318X+22.45±2.98 (r2 = 0.36, n = 12, MSE = 38.02, CV = 21.9, p<0.01) for swamp buffaloes and Y = 0.96±0.10X+15. 93±0.92 (r2 = 0.91, n = 12, MSE = 3.60, CV = 8.27, p<0.01) for zebu cattle. The salivary PD concentration was not correlated with intrajugular allantoin infusion in both species, with values for buffaloes numerically lower than those for cattle. The present study reconfirmed previous studies that buffaloes have a lower plasma PD excretion rate via the renal route and a significant proportion (22%) of the plasma PD loss is via the saliva. However, results of our present and previous studies suggest that differences in purine base (PB) metabolism between buffaloes and zebu cattle occur before the purine compounds reach the plasma pool