The goal of the present study is to evaluate the effect of feed restriction on chromosomal pictures, serum biochemical  parameters and some hormones in addition to spermiogram with their reflection on the reproductive efficiency of rams. Five mature Crossbred (Barki x Rahmant) rams were used, their age ranged from 15 to 17 months and weighting 45 to 60 kg. Rams received a basal diet according to the management of Animal Reproduction Research Institute (ARRI). The animals were exposed to 21 days of feed restriction (1/3 amount of basal diet). Restricted rams refed again on basal diet for 14 days. Blood and semen samples were collected from rams (before feed restriction, 21 days after feed restrictionand 14 days post refeeding). The results showed that there were significant differences between first period and others in the percentage of some chromosomal abnormalities which mainly polydiploidy, in addition to gaps, breaks, deletions and fragments which increased significantly only after feed restricted periods in addition to the significant increase in the percent of total number of aberrated cells. Concerning the biochemical parameters in there was a significant decrease in serum glucose and cholesterol levels after feed restriction and they were elevated after refeeding to their levels before the restriction.  Malondialdehyde showed a significant decrease after refeeding than the other two periods of the experiment. On the contrary, there was a significant increase in serum insulin levels after feed restriction compared with the other two periods.  The effect of feed restriction was clear on serum testosterone hormone level which showed significant) decrease after feed restriction and after refeeding. There was significant decrease in semen volume after restriction and refeeding cams. There was significant decrease in the motility and live/dead sperm after feed restriction and return to their levels post refeeding. Concentration of semen showed significant decrease after both feed restriction and refeeding.Total sperm abnormalities showed significant increase after restriction and back to first level before restriction. It was concluded that, feed restriction (1/3 amount of basal ration) for 21 days in mature rams has adverse effect on the chromosomal pictures, some biochemical parameters and decreased testosterone level in addition to decrease in all semen parameters. This effect was not overcome by supplemental feeding again that confirming the status of these rams did Hot improve completely even after the tested refeeding period.