Abstract:
The food for ruminants; forages and fibrous roughages,
consist mainly of |3-linked polysaccharides such as
cellulose, which cannot be broken down by mammalian
digestive enzymes. Ruminant have therefore evolved a
special system of digestion that involves microbial
fermentation of food prior to its exposure to their own
digestive enzymes. The rumen microbes can use simple
compounds such as ammonia and to make their cells
which in turn provide the animal with most of its protein
need. The purines from the rumen microbes are
metabolised and excreted in the urine as their end
products: hypoxanthine, xanthine, uric acid and
allantoin. That is why the research work has been carried
out actively for the past 20-30 years into the urinary
excretion of these purine metabolites, with an objective
to use the excretion of these metabolites as a parameter
to quantitatively estimate the supply of rumen microbial
protein to the ruminant. Recently several studies in the
field have concluded that buffaloes have much lower
(and more variable) urinary excretion of purine
derivatives (PD) per unit DOMI than cattle (Chen and
0rskov, 2004), but the mechanisms were not fully
understood.
