For instance, a cow directly consumes about twice the forage as an elk. Since the majority of forage in the West, even on public lands, is allotted to cows, this significantly reduces the amount of elk, deer, and other big game biomass. This has substantially reduced the carrying capacity of all our lands for native predators and scavengers. Fewer elk, for instance, means less food for grizzlies and wolves. It means less carrion for ravens and coyotes.
Livestock also affect wildlife through social displacement.
Elk, for instance, will avoid area actively being grazed by cows. This could preclude use of the best habitat by these native species all to benefit an exotic species. Livestock are also one of the major vectors for diseases transmitted to native wildlife. From mad cow disease that causes deer and elk brains to turn to mush to pink eye that causes bighorns to go blind, the transmission of disease from domestic animals to wild animals often has disasterous consequences. Because livestock are vulnerable to predators, ranchers have essentially eliminated predators from the West.