Effects of different levels of selenium on performance and some blood parameters of feedlot kids

Selenium is a trace element in feeding animals. Selenium is an essential component of thyroid hormones metabolism and plays an important role in the formation and activity of antioxidant enzyme glutathione peroxidase. Although selenium deficiency occurs in all animal species, ruminants, and especially small ruminants, such as sheep and goat, are more susceptible to this disease, which is associated with damage to myocardial infections in lambs and kids, and muscle lesion in younger ones. In the absence of selenium, it affects skeletal muscle and liver tissue, which results in increased Creatine phosphokinase activity and amino-aspartate transferase in tissue and plasma. Therefore, the aim of this study was to investigate the effect of different levels of selenium supplementation on the performance and blood of feedlot kids.
Material and This trial was conducted to evaluate the effects of different level of selenium supplements on growth performance, hematological and plasma parameters in feedlot kids for 60 days. The experiment consisted of 18 kids, 4-5 months of age and 22.52±5.02 kg average in weight randomly allotted to 3 treatments. Treatments were: 1) Control diet (diet without selenium supplementation); 2) Control diet + 0.15 mg/kg Se as sodium selenite and 3) Control diet + 0.30 mg/kg Se as sodium selenite. Kids were weighted in the beginning and on days 15, 30, 45 and 60 and daily feed intake for each animal was measured. Blood samples were taken on days 30 and 60 and plasma concentration of calcium, phosphorus, zinc, copper and iron, aspartate amino transferase, alkaline phosphatase, alanin amino transferase, creatine phosphokinase activities, serum triiodotyronin, tetraiodotyronin levels and blood gluthation peroxidase activity were measured. According to obtained results, average daily feed intake and body weight were not significantly different between treatments (P>0.05), but average daily gain in 0.30 mg/kg group was significantly increased in compare to control group. Feed conversion ratio was improved in selenium groups (P<0.05). Serum concentrations of aspartate amino transferase, alkaline phosphatase, alanin amino transferase and creatine phosphokinase activities, plasma concentrations of calcium, phosphorus, zinc, copper and iron were not significantly different among groups (P>0.05). Concentrations of triiodotyronin and gluthation peroxidase activity were significantly increased and concentration of tetraiodotyronin and triiodotyronin/tetraiodotyronin ratio decreased in selenium supplemented groups (P<0.05). In conclusion, supplementation of 0.15 and 0.30 mg/kg selenium resulted in increased average daily gain and improved feed conversion ratio, thyroid hormones metabolism and antioxidant status of feedlot kids.