Influence of Different Ratios of Cobalt and Copper Supplementation on Vitamin B12 Status and Nutrient Utilization in Sheep

The present study is aimed to investigate the effects of different ratios of cobalt (Co) and copper (Cu) supplementation on vitamin B12 status and nutrient utilization in sheep. Twenty wether lambs with an average weight (22.9 ± 0.8) kg were randomly divided into five groups and fed with the control diet which was supplied with 0.3 mg kg-1 DM (dry matter) of Co to the basal diet, and four supplemental diets which were supplied either 0.3 or 0.6 mg kg-1 DM of Co and 10 or 20 mg kg-1 DM of Cu to the basal diet, respectively for 8 wk. The supplementation of Co and Cu with different levels improved plasma vitamin B12 concentration which was increased with feeding time, but stable after 6 wk. Vitamin B12 status was accounted for Co intake with no combined effects by supplementation of different levels of Co and Cu. The plasma concentrations of methylmalonic acid, homocysteine, folic acid, and glucose did not show the consistent results with plasma vitamin B12, which was considered to be resulted from Cu action. Addition of Co and Cu with different levels had no influence on digestibility of dry matter (DM), organic matter (OM), crude protein (CP) and nitrogen free (NFE), and N metabolism (P> 0.05), but the digestibility of fat and fibre (P<0.01) was enhanced by supplementation of 0.3 mg kg-1 DM of Co and 20 mg kg-1 DM of Cu. In conclusion, the supplementation of Co and Cu with different levels has no influence on vitamin B12 status. The optimum ratio of Co and Cu in diet could enhance the nutrient utilization.