The aim of this study is to determine the effects of boron supplementation in ration of rams on their productive activity and semen quality. For that purpose, twelve rams were divided into two groups (6 rams/ each). Rams of the first control group were fed the basal ration. Concerning the second group (boron group), the rams were fed the basal ration plus 400 mg boric acid (BA) / kg diet as a source of boron. The rams in both groups fed their corresponding ration for 4 months ad libitum. Blood samples were collected monthly throughout the experimental period. Semen samples were collected at the 12th and 16th weeks of the experiment. The results clarified that the serum levels of tetraiodotyrosine (T4) were observed to be elevated significantly (P<0.05) with growing of age in the rams fed B, but they didn't change in the control group. In addition, the semen quality was maintained normal with boronsupplementation as the individual sperm motilities and live/dead sperm cells percentages were similar to control. Also, boronsupplementation didn't induce any adverse effects on the serum levels of Mg when compared to control group. Thus, boronis considered a potential and useful supplement in ration of rams to improve the thyroid activities and didn't induce any adverse effects on either semen quality or serum magnesium level in rams.