The objective of the investigation was to determine different potentials of urine purine derivatives (PD) and
estimated microbial nitrogen synthesis (MNS) in domestic herbivores raised in the Mekong Delta for future
applications. The domestic herbivores used in the study included 4 buffaloes (284 ± 12.3 kg), 4 cattle (146 ± 8.6
kg), 6 goats (21.1 ± 3.76 kg), 6 sheep (21.5 ± 4.27 kg) and 10 rabbits (1.88 ± 0.023 kg). Diet used for feeding
buffalo was rice straw, natural grass, sesbania grandiflora and urea-molasses, for cattle was rice straw mixed
with molasses and minerals, for goat was Para grass, for sheep was panicum maximum and concentrate and for
rabbit was Para grass, sweet potatoes vines and concentrate. The investigation period was 3 weeks with 2 weeks
for dietary adaptation and one week for measurements.
The results showed that daily excretions of allantoin, uric acid and purine derivatives (mmol/kgW0.75) in urine
and estimated MNS (gN/kgW0.75) of the animals were variable among the herbivore species. The MNS
(g/kgW0.75) were 1.11, 0.479, 0.123, 0.112 and 0.038 for buffaloes, cattle, sheep, rabbits and goats. Although the
CP intake (g/kgW0.75) of rabbits was higher than cattle, sheep, buffalo and goats, the PD (mmol/kgW0.75) were
higher for the cattle (0.705) and buffaloes (0.384) compared to the others. Especially in case of buffalo the urine
PD excretion and MNS produced could be driven by the characteristics of its physiology and nutrient
metabolisms. It was preliminarily concluded that PD excretion and the estimated MNS of the herbivores were
crucially influenced by different species and protein intake level.

Keywords: excretion, ruminals, feed intake, digestion