Abstract :
When ruminants consume feed, as much as half of the amino acid nitrogen can be lost due
to microbial degradation in the rumen. Hyper ammonia-producing bacteria (HAB) are primarily
responsible for amino acid loss in sheep and cattle, and ionophores (e.g. monensin)
are used to inhibit the HAB. Ionophores are sometimes included in the diets of meat goats,
but the effects on caprine HAB have not been investigated. Five amino acid catabolizing
bacteria were isolated from the rumina of Boer goats, which were consuming a supplement
that contained monensin. Two of the isolates were most closely related to the bovine
HAB, Peptostreptococcus anaerobius, but the other three were more closely related to Peptoniphilus
indolicus. When the isolates were exposed to monensin, intracellular potassium
was lost, and ammonia production was inhibited. However, the P. indolicus-like isolates
demonstrated a greater capacity to overcome this inhibition in growth experiments. These
results indicate that the monensin sensitivity of these bacteria can be variable, even when
previous exposure to monensin occurred in the rumen environment
