Fifteen sheep and 15 goats were fed isonitrogenous amounts (7.2g N day-1) of A. nilotica, A. seyal and S. sesban as supplements to ad libitum allowance of tef straw in a randomized block design. Sheep consumed more straw and total DM than goats fed on the same browses. Digestibility of DM and NDF were higher (P < 0.05) in goats than in sheep. Differences between browse species in intake of straw were not observed; however apparent N digestibility, rumen ammonia, and N retention were consistently lower in animals fed A. seyal than when animals were fed A. nilotica and S. sesban. It was concluded that differences in intake between sheep and goats could be attributed to differences in retention times and hence digestibility of DM and NDF. Differences between browse species are attributed to types and levels of tannin and related polyphenols in the leaves; and their effect on N metabolism in the rumen. Use of the faecal N fractionating technique as a non-invasive method of determining N degradability in ruminants may not be applicable to high tannin feeds.