Laboratory evaluation of phosalone and diazinon on fermentation parameters and some rumen microbial population

Organophosphate (OP) compounds such as phosalone and diazinon are a diverse group of chemicals used against a wide range of agricultural pests. Ruminant animals are raised in environments that may expose to a wide variety of pesticides. Exposure of animals to these types of pesticides may be intentional, such as the dermal application of various pesticides for control of insect and parasite infestation, or exposure may be accidental, such as the consumption of chemically-contaminated feed. The first concern is the potential deleterious effect of the chemical on the animal health. The second concern, particularly to animal food producers is health of livestock products. So the purpose of this experiment was to study the effect of diazinon and phosalone on the fermentation parameters, protozoa population and a ruminal fibrolytic bacteria species (Butyrivibrio fibrisolvens) in the culture medium using real-time PCR.
Phosalone and diazinon, two organophosphate pesticides at three levels (0, 100 and 500 ppm) and sodium bentonite at two levels (0 and 2% of diet DM) were used with a factorial experiment 2×3×2 in a laboratory media according to completely randomized design. The gas production was measured and the some parameters were also estimated by the cumulative gas production technique. The total protozoa and the ruminal bacterium Butyrivibrio fibrisolvens in the culture medium were determined by the real-time PCR.
The cumulative gas production after 12, 24 and 48 h of incubation, and also the rate (cgas) and potential gas production (bgas) were significantly decreased when phosalone or diazinon were added to the culture medium. Adding phosalone and diazinon to the culture medium were significantly decreased the total estimated parameters such as organic matter degradability, metabolizable energy, net energy for lactation, microbial protein yield and shortchain fatty acids. Adding sodium bentonite (2%) to the culture medium also resulted in a significant decrease in the above-mentioned parameters. The protozoa population was significantly decreased following application of two pesticides to the culture medium, but ruminal bacterium Butyrivibrio fibrisolvens was not affected by the type of pesticide. Application of sodium bentonite in the culture medium also decreased significantly the population of protozoa and ruminal bacterium Butyrivibrio fibrisolvens.
Using both diazinon and phosalone had negative effects on the gas production, estimated parameters and total protozoa. Toxicity of phosalone on the culture medium was more in comparison to diazinon. Sodium bentonite as a toxin-binder could not decrease the negative effects of both phosalone and diazinon in the culture medium and resulted in negative impacts on the gas production, estimated parameters, ruminal bacterium Butyrivibrio fibrisolvens and total protozoa.