Different types of forage have been used worldwide in farm animal feeding. However, different microscopic cellular arrangements are clear in the anatomical structure, are due to climatic influences and are reflected in the productivity responses of cattle, especially in comparisons among tropical and temperate grasses. The physical impediment of the plant anatomical structure affects nutrient accessibility to rumen microorganisms. Thus, the objective of the present review was to discuss aspects related to C3 and C4 forage plant anatomy and nutrient availability for ruminants, due to the specific structure of each plant tissue, the speed at which the microorganisms can access the cells becomes different animal responses. Key words: Plant anatomy, digestibility, nutritional value, neutral detergent fiber.