Reasons for low productivity of sheep grazing barrel medic (Medicago truncatula) were investigated based on studies of intake and digestion. Pasture analysis showed that barrel medic represented only 13 to 30% of the diet selected and this was similar to its proportion in the green feed on offer. The selected diets had relatively low ratios of DOM to CP and the high levels of rumen NH₃ and wastage of dietary protein in the stomach were predictable. The amounts of amino acids derived by sheep on these diets were much lower than the CP intake suggested and undoubtedly contributed to the relatively low levels of wool production.