REPRODUCTIVE & PRODUCTIVE PERFORMANCE OF MALE LAMBS SUPPLEMENTED WITH DIFFERENT SELENIUM SOURCES

SUMMARY
The aim of this study was to evaluate the reproductive performance of male lambs, digestibility and feeding values of rations as affected by supplementation of different selenium (Se) sources. Twenty-four healthy Sohagi male lambs of (7-8 month old and 24.47±0.15 kg body weight) randomly assigned into four groups (6 animals each).The experiment extended for 25-weeks after two weeks for adaptation. Basal diet was formulated to meet the nutritional requirements according to NRC (1985) except Se. Lambs in the first group fed basal diet as a control whereas lambs in groups T2, T3, and T4 were fed the basal diet supplemented with 0.1 mg/kg DM sodium selenite, vitamin E and selenium and selenized yeast, respectively. Three rams of each group (averaged 44.21 ± 4.90 kg body weight) by end of feeding trial were placed in metabolic cages to evaluate the digestibility and feeding values of the experimental rations. Five-days preliminary period followed by ten days collection period with quantitative collection the faeces. 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 (T4) had higher DM, OM, CP, EE and NFE digestibility coefficients than the other three treatments and the differences almost were significant in most nutrients between T4 and each of T2 and control. Generally, digestibility coefficients of DM were 66.66%, 68.94%, 70.31%, and 71.98% for control, T2, T3 and T4, respectively. Also, the values of TDN and DCP behaved similar to digestion coefficients of all nutrients . The present results illustrated that testes weight recorded higher value in T4 ,T3 , T2 compared to control, but the differences among treatments were not significant . In addition, the concentrations of selenium in testes were significantly (P<0.01) higher in T4, followed by T3 and T2, while the lowest value was recorded in the control group, 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 non significant differences among treatments, while at 1, 2, 3, 4 and 5 months of experimental period, T4 group recorded higher (p<0.01) to 0.05) values for the three mentioned testes parameters of T3, T2 and control treatments. Generally, T4 and T3 recorded higher significant values in comparison with T2 and control . Also, data showed that both diameter of testes and testosterone concentration increased with advancing of age. In addition, values of 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 T4 (selenized yeast) and T3 (vitamin E and selenium) showed significantly higher activity of both thyroid hormones in comparison with T2 (sodium selenite) and control 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 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.