As other ruminants, buffaloes utilize micro-organisms in the rumen to digest
the feed. In buffaloes a higher rumen degradability of nitrogen and carbohydrates in
concentrates promotes the growth and the synthesis of rumen bacteria, even when fed
diets with low protein content. It appears that buffaloes use more efficiently nitrogen
coming out from rumen fermentation and metabolism and by recycling it. This efficient
accommodation to more limiting feeding condition is enhanced by a higher availability
of purine derivatives (PD) of metabolic origin. Many measurements done on buffaloes
of various breeds have shown a lower PD nitrogen excretion in urine. In buffaloes,
urinary PD excretion is not linked to i) the availability of microbial cells in the rumen
or ii) small intestine uptake of purines. Such PD excretion seems to be related more to
tissue metabolism differences of which the mechanisms are not yet fully understood.
Some explanation is emerging with new studies on swamp buffaloes, summarized in
the following two: i) in the first study, weaning of swamp buffalo and cattle calves was
accomplished by colostrum administration, and rearing followed by milk bottle
feeding. To assess differences in the endogenous secretion of purines, urine samples
from the two species were collected. Solid food was not made available in the course of
the first month, but access to it was granted in the course of the intervening 2
successive months in order to stimulate rumen development. Then a mixed ration of
purines and milk was given to the animals, together with an infusion of intravenous
allantoin, so that the effect of the introduced purines in the plasma could be tested.
From the results obtained in the course of the suckling period, no differences between
the two species in purine excretion was reported. Following rumen development
though, purine excretion from buffaloes was less than half when compared to cattle,
and likewise, following allantoin infusion, purine recovery in buffaloes was half the amount when compared to cattle ; ii) in the second study in the course of fasting and
bottle milk feeding, a determination of urinary PD, basal PD excretion and glomerular
filtrate (GFR) rate was made. Following access of the animals to solid feed, an
assessment of urinary PD, basal PF excretion and glomerular filtrate rate was also
performed. No significant differences were observed between the two species in the
course of the milk feeding period in terms of urinary PD excretion, although the same
differences were highly significant between the two species at 3 months of age and
following 2 months of access to solid feed. In buffaloes, both during the milk feeding
and following solid food access, GFR was found lower in buffaloes when compared to
cattle. To date it can be stated that some studies report a higher rumen fluid NH3
concentrate in swamp buffaloes in comparison to yellow cattle. Other studies have
shown that only following rumen development, a difference in PD excretion can be
seen, and the difference between buffaloes and cattle is due to differences in GFR, so
that more urea and PD are recycled, highlighting the fact that buffaloes can tolerate less
N in the feed to satisfy microbial needs.
Keywords: Buffaloes, Feeding, GFR, Microbial protein, Purine derivative, Rumen, Rumen NH3
