Most vertebrate herbivores are relatively general in diet. Even Bison , which subsist largely on grasses, not only use a wide variety of those but also feed on herbaceous dicots. These animals rely on gut microbes for detoxification and digestion of the plants they eat. They tend to switch between plant species during feeding, a behavior that reduces the chances of eating too much of any one plant's defensive compounds. Their fungus gardens inside the nest contain fungi which convert leaves to fungal products which the ants eat.
Cows feed grass to their gut bacteria and digest the bacteria and their products.
Flea beetles and some caterpillars simply eat holes in young leaves and are minor parasites as long as their own biological controls are operating. Aphids are sucking insects of new shoots and can damage new leaves and reproductive parts. Some insects, regardless of size are effective predators of seeds. These include sucking bugs such as these coreids feeding on thistle seeds, and beetles such as weevils and bruchids which develop inside seeds. Seed pods of plants like mesquite often show exit holes of emerging beetles.