Effect of some pesticides and herbicides on the rumen micro-organisms of sheep

Lower concentrations of the herbicide M15 stimulated the in vitro cellulose digestion and V.F.A. production by rumen micro-organisms. The herbicide Cotoran enhanced cellulose digestion but had no effect on V.F.A. production. The herbicide Dalapon decreased cellulose digestion and had little effect on V.F.A. concentrations. The herbicide 2,4·D had little or no effect on the in vitro cellulose digestion and V.F.A. production. The in vitro microbial activity was inhibited by the pesticide DDT. The effects of M15 2,4·D and DDT on V.F.A. production decreased with time. When the rumen fluid was fractionated, the V.F.A. production by the bacterial fraction was not significantly altered by the addition of 2,4·D and M15, whereas the activity of protozoal fraction was greatly enhanced. The response of V.F.A. production by washed suspensions of rumen ciliate protozoa to the addition of pesticides and herbicides was remarkably similar to that of rumen contents. Feeding M15 (60 ppm) increased the ruminal V.F.A. over those in the control sheep whereas 2,4·D had no or little effect.