EFFECTS OF GRAZING SYSTEM AND PARASITE CONTROL WITH IVERMECTIN ON NEMATODE BURDENS AND BEEF-PRODUCTION OF STOCKER STEERS

The primary objectives of this study of 180 English crossbred stocker steers were: to determine the influence of parasite control with iverm ectin (Ivomec(R):MSD AgVet, Rahway, N.J.) on weight gain performance i n stocker steers grazing either intensively or conventionally managed, improved pastures; to determine the effect of an intensive grazing ma nagement system on the exposure to internal nematodes in stocker steer s compared to a conventional grazing management system; and to measure productivity of stocker beef steers as determined by beef production per acre, using these different grazing systems while comparing a stra tegic parasite control program using ivermectin to a maximum parasite control program (positive controls) using ivermectin. Data from this s tudy suggest that a strategic parasite control program, using ivermect in for stocker beef steers in the Midwest, may allow gain performance similar to that in beef steers given maximum parasite control.