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Four rations were formulated to be iso-nitrogenous and iso-caloric and represent different nitrogen sources. These were cotton seed cake (CSC), sesame seed cake (SSC), groundnut cake (GNC) and sunflower seed cake (SFSC). The effect of the different nitrogen sources on rumen fermentation pattern, digestibility, blood urea nitrogen (BUN), BW changes and N retention was studied using 32 yearling desert rams. There were two experimental periods covering feeding trials where the BW changes were monitored over 12 weeks and digestibility trial where the animals were placed in metabolism cages for the determination of digestibility, rumen components, BUN and N retention.

Average daily gain of 96.7, 87.5, 76.3, and 72.9 g per day for SFSC, SSC, CSC, and GNC, respectively, showed that SFSC had the best gain (P < 0.05). Feed conversion ratio was higher (P < 0.05) with CSC and GNC rations than SSC and SFSC. Ruminal VFAs and ammonia N concentrations were the highest (P < 0.05) with CSC compared to the other rations either before or post-feeding. Ruminal pH or BUN level were not affected by the different N sources imposed. Lipid digestion was reduced (P < 0.05) with the GNC ration while N retention was reduced (P < 0.05) with the SSC ration. Provision of different N sources using different oil seed cakes in the ration of yearling sheep showed that owners’ preference of CSC and GNC-SSC and SFSC cakes could be related to the better conversion ratios obtained by the two former oil cakes. (C) 2003 Published by Elsevier B.V.