الفهرس 
INTRODUCTION
Effect of different selenium sources on growth performance of lambsOnly 14 pages are availabe for public view
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Abstract
A total number of twenty-four healthy Sohagi male lambs of about 7-8 month of age were randomly assigned into four dietary treatment groups (6 animals each). The experiment was extended for 25-wk after two weeks adaptation period. All Lambs were fed on the experimental diet, which was formulated according to NRC (1985) for sheep. The basal diet consists of 30% wheat straw and 70% concentrate mixture. It was formulated to be adequate in protein, energy, vitamins and minerals for this class of animals except for Se content. Lambs in control group were fed a basal diet, whereas lambs in groups T1, T2, and T3 were fed the basal diet supplemented with 0.1 mg Se/kg DM from sodium selenite, vitamin E and Selenium and selenized yeast, respectively. Blood samples were collected before offering feed and water throughout experimental period at d 0, 30, 60, 90, 120, and 150 of the experiment and tissue samples were collected at experiment termination. Tissue and blood Se concentrations, blood glutathione peroxidase (GSH-Px) activities, and plasma interleukin levels were analyzed. At the end of experimental trail, three rams from each group (average body weight 44.21 ± 4.90 kg) were placed in metabolic cages. Five days preliminary period were followed by a collection period of ten days. Quantitative and separated collection of faeces was measured and stored for digestibility coefficient of nutrients and nutritive values of different tested rations. Also, three animals from each group were randomly chosen and slaughtered at the end of the experiment to investigate the effect of different Se sources on carcass characteristics. The results showed that the body weight and daily gain of lambs recorded the highest (p<0.05) values in T3 (24.17%) followed by T2 (18.24%) and T1 (8.53%) compared to control. The corresponding values for daily gain were 56.28%, 43.76% and 22.81% in T3, T2 and T1 resp. The activities of GSH-Px and the concentrations of Se in blood increased in all of the supplemented groups during the period of supplementation (p < 0.01) compared with the control group. The activities of GSH-Px and the concentrations of Se in the whole blood of the lambs fed with selenized yeast and vitamin E and Selenium were higher than those of lambs fed with sodium selenite (p<0.01 or p<0.05). The concentrations of interleukin-1 and interleukin-2 in plasma significantly increased in all of the supplemented groups during the entire period of experiment (p<0.01) compared with the control group, but had no significant differences among all of the supplemented groups. Selenium yeast (T3) had positive significant (P <0.05) effect on digestibility coefficients of DM, OM, CP, EE and NFE, while CFD was not significantly affected. There were no significant differences between T3 and T2 treatments in digestibility coefficients of DM, OM, CP, EE, NFE and nutritive values (TDN and DCP %). The average slaughter weight of rams fed T3 treatment was significantly (p<0.01) higher than those fed either T2 or T1 in comparison with control group. Empty body weight of rams fed T3 treatment was significantly (p<0.01) higher than those fed either T2 and T1 as well as control one, Also hot carcass weight, dressing % (A), right and left side in T3 was significantly (p<0.01) higher than those fed T2, T1 and control groups. Also, the results revealed that lambs fed T3 treatment had the highest weight of liver, kidneys, testes, spleen, heart, lungs and trachea, total edible offals, internal fat, kidneys fat, total fat, but the differences due to source of selenium were not significant. Eye muscle area (longissimus dorsi) of the T3 treatment was higher by 12.73 % than control group, but the differences due to different Se sources were not significant. Similar trend was observed for samples of meat and fat weights, meat and fat percentages as well as meat: fat ratio, fat, and meat in carcass. Se concentrations in the kidney, liver, spleen, lungs, heart, testes and eye muscle area in all of the supplemented groups were significantly (p < 0.01) higher than those in unsupplemented (control) group. However, the Se concentrations in in the kidney, liver, spleen, lungs, heart, tests and eye muscle area in the groups supplemented with T3 and T2 were higher than those in the group supplemented with T1 (p < 0.01). In conclusion, selenium supplementation both sources of selenium (organic and inorganic forms) improved both the digestibility coefficiency and nutritive values of tested rations and also, productive performance of finishing lambs (body Weight, average daily gain, feed conversion efficiency and protein efficiency). In addition, selenium in the organic form into growing lambs’ diet improved some carcass parameters, specifically, Se supplement above NRC (1985) recommendation as selenized yeast enhanced commercial and biological yield of sheep.
Control= without treatment
T1= sodium selenite treatment.
T2= vitamin E and selenium treatment.
T3= selenized yeast treatment.