In this study, the effects of diets which contained alfaalfa hay (group 1), barley straw (group 2) or HCI- treated straw (group 3) as roughage and concentrated feeds (50 : 50) on digestibility andN-retention on goats were determined. At the end of the experiment, digestibilities were 70.95, 64.97 and 67.78 % for dry matter (P < 0.01), 72.48, 65.59 and 67.85% for organic matter (P < 0.01), 52.54, 54.13 and 57.74% for crude fiber (P > 0.05), 73.68, 78.86 and 79.34 %for crude protein (P < 0.01), respectively, in the groups. On the other hand, the N-retention values were 5.11, 6.59 and 7.54 g/day (P > 0.05), respectively. In general, the treatment of barley straw with HCI increased nutrient digestibility (P < 0.05) andN-retention (P > 0.05).