SOME REPRODUCTIVE PERFORMANCE OF MALE LAMBS AND FEEDING VALUES OF RATIONS AS AFFECTED BY SUPPLEMENTATION OF DIFFERENT SELENIUM SOURCES

The aim of this study was to evaluate some reproductive performance of male lambs, digestibility coefficients and feeding values of rations as affected by supplementation of different selenium (Se) sources. Twenty-four healthy Sohagi male lambs (7-8 month old and 24.47±0.15 kg body weight) were randomly assigned into four dietary treatment groups (6 animals each).The experiment was extended for 25-weeks after two weeks as adaptation period. Basal diet was formulated to meet the nutritional requirements according to the NRC (1985) except Se. Lambs in the first group were fed a basal diet as a control (T0) without supplement whereas lambs in groups T1, T2, and T3 were fed the basal diet supplemented with 0.1 mg/kg DM sodium selenite, vitamin E and selenium and selenized yeast (Se-yeast T3) , respectively. Three rams from each group (average body weight 44.21 ± 4.90 kg) of feeding trial were placed in metabolic cages for perform four digestibility coefficients trials to evaluate the digestibility  and feeding values of the experimental rations. Five-day preliminary period was followed by a collection period of ten days with quantitative collection the feces. Blood samples from three animals in each group were collected before offering feed and water throughout the experimental period at 0, 1, 2, 3, 4 and 5 months of the experimental period . Results showed that ration supplemented with selenized yeast (T3) had a higher DM, OM, CP, EE and NFE digestibility coefficients than the other three treatments and the differences mostly were significant in most nutrients between T3 and each of T1 and control (T0) group. Generally, digestibility coefficients of DM were 66.66%, 68.94%, 70.31%, and 71.98% for control (T0), T1, T2 and T3, respectively. Also the values of TDN and DCP were behaved similar trend among dietary treatments as well as the digestion coefficients of all nutrients. The present results illustrated that testes weight recorded higher values in T3, T2, T1 compared to control group (T0), but the differences among treatments were not significant. In addition, the concentrations of selenium in testes were significantly (P<0.01) higher in T3, followed by T2 and T1, while the lowest value was recorded in the control group (T0), with significant difference between each other. Also, results illustrated that values of testes circumference, testes volume and testosterone concentration  at the beginning of experiment showed no significant differences among treatments, while at 1, 2, 3, 4 and 5 months of experimental period T3 group recorded higher (p<0.01) or values of   three mentioned testes parameters compared  with T2, T1 and control  (T0) treatments. Generally, T3 and T2 recorded higher and significantly values in comparison with T1 and control group (T0). Also, data showed that both diameter of testes and plasma testosterone concentration increased with advancing of age. In addition, values of plasma thyroid hormones concentrations recorded significantly(p<0.01) higher values as a results of supplementation of different sources of selenium compared to control group. Moreover, concentration of both hormones in T3 selenized yeast (Se-yeast) and T2 (vitamin E and selenium) showed significantly (p<0.01)  higher activity of both thyroid hormones in comparison with T1 (sodium selenite) and control (T0) groups. Also, both hormones concentrations increased with advancing age. It can be concluded that supplementation of selenium in the ration of sheep especially in the form of selenized yeast (Se-yeast)  led to an   improvement in nutritive value of rations and reproductive performance through the favorable effects on  weight, testes diameters and testosterone concentration as well as the thyroid hormones concentrations in blood of male lambs.