PURINE DERIVATIVE EXCRETION AND RUMINAL MICROBIAL YIELD IN MALAYSIAN CATTLE AND SWAMP BUFFALO

Allantoin concentration was measured in urine (n = 115) of Malaysian indigenous Kedah Kelantan (KK) cattle (Bos indicus) and swamp buffalo (Bubalus bubalis). The rectilinear relationships between allantoin excretion (Y, g N day-1) and digestible dry matter (DM) intake (X, kg day-1) for KK cattle and swamp buffalo were Y(cattle) = 0.238 + 0.836X (R2 = 0.76, P < 0.01) and Y(buffalo) = 0.181 + 0.466X (R2 = 0.65, P < 0.01). These relationships adjusted for body weight (kg0.75, BW) and intake: BW ratio had lower R2 Values. No significant difference was detected between the intercepts (minimal endogenous allantoin excretion) of the rectilinear relationships, but the slope (allantoin excretion rate per unit food intake) for KK cattle was greater (P < 0.01) than for swamp buffalo. In a second study, total purine excretion of fed, fasting and refed KK cattle and swamp buffalo was measured. Hypoxanthine + xanthine excretion by KK cattle and swamp buffalo was less than 3% of the total purine excretion. The KK cattle excreted three times as much allantoin as swamp buffalo when fed at 1% of DM of their BW (1.74 g N day-1 vs. 0.60 g N day-1), but allantoin excretion at the end of 6 days of fasting was not significantly different between species. Uric acid excretion was generally higher (P < 0.05) for swamp buffalo than for KK cattle during fasting, but species differences were not consistent during the fed and refeeding periods. Total purine excretion of fed KK cattle was higher (P < 0.05) than of fed swamp buffalo. The difference in allantoin and total purine excretion rates between KK cattle and swamp buffalo given the same diet and level of feeding is apparently the result of physiological and/or ruminal microbial differences between the species.