Improving the nutritive value of straws and other crop residues is a priority research area for countries where smallholder farmers manage most ruminant livestock. The most important determinant of nutritive value is digestibility because it correlates highly with voluntary feed intake and thus indicates the quantity of digestible nutrients the animal is receiving. This project will develop a technique of genetic marking to assist mapping of desired traits in the grasses, as a basis for later manipulating the characteristics of cell walls of the residues to render them more digestible and thus to increase their nutritive value. The target species are two cereals (barley and pearl millet) and two pasture grasses (perennial ryegrass andBrachiaria).