Assessment of different cobalt concentrations in the diet of fattening lambs: Effect on performance, some blood metabolites and rumen fermentation parameters

In order to evaluate the effect of cobalt on performance, some blood and ruminal fermentation parameters an experiment was performed using 24 three to four months old male lambs, with an average weight of 30 kg in a completely randomized design with four treatments and six replications. The experimental treatments consisted of: basic diet (control; containing 0.083 mg cobalt /kg DM); basal diet + 0.2 mg Cobalt /kg DM, basal diet + 0.4 mg cobalt /kg DM, and basal diet + 0.6 mg / kg of cobalt. In order to determine blood parameters on days 0, 45, 70, blood samples were collected from jugular vein and ruminal fluid through the esophagus were taken to evaluate ruminal fermentation parameters. Cobalt supplement had no significant effect on daily gain, dry matter intake, feed conversion ratio, serum B12, cholesterol, triglyceride and albumin and also alkaline phosphatase and alanine transaminase. Ruminal ammonia concentration increased at the level of 0.2 and 0.4 (P<0.05), but concentration of volatile fatty acids, rumen pH and protozoan population did not influence. The concentrations of cobalt, iron, zinc and copper minerals were not affected by treatments. The results of the present study showed that adding cobalt supplementation to the diet up to the level of 0.6, despite limited changes in some blood and ruminal parameters did not have a significant effect on the performance of lambs; it seems that the cobalt in the basic diet could be sufficient for the cobalt requirements of growing Sanjabi lambs.