The effect of long-term exposure to phosphamidon on the ruminal microorganisms and circulating carboxylesterase ofBubalus bubalis

The effect of long-term exposure to the organophosphate insecticide phosphamidon on the ruminal microorganisms and serum carboxylesterase of buffalo calves was investigated. Oral administration of phosphamidon in doses of 0.25 and 0.5 mg/kg per day for 120 days caused significant inactivation of carboxylesterase activity (16–32%) without eliciting any intoxicating signs apart from mild intermittent diarrhoea in the animals receiving the higher dose. The higher dose also produced a significant reduction in the total number of rumen protozoa (16–24%). However, the insecticide had no discernible effect on the total bacterial count or pH of the rumen liquor.