Effects of Feeding Canavalia ensiformis on the Rumen Flora of Sheep, and of the Toxic Amino Acid Canavanine on Rumen Bacteria

Abstract

Feeding Canavalia ensiformis to sheep was accompanied by a decrease in the concentration of ammonia and valerate in the rumen, and by an increase in the relative proportion of Gram-negative rumen bacteria. The rumen pH, viable counts of bacteria and fungi, and the degradation of rice straw incubated in the rumen in nylon mesh bags, was not affected by feeding Canavalia. No toxic effects were observed. Studies with canavanine suggested that this component of Canavalia was unlikely to be responsible for the observed shift in the rumen microbial population, as the bacterial response to canavanine was not correlated with the bacterial staining characteristics. A number of canavanine-degrading bacteria were isolated, and it seems that these organisms degrade sufficient of the dietary canavanine so that the toxic effects of this compound are avoided when ruminants eat Canavalia.