关键词: 绵羊, 钴, 维生素B12, 消化代谢

Abstract:

【Objective】 The experiment was carried out to study the effects of different cobalt (Co) and copper (Cu) supplementation on vitamin B12 status and nutrient utilization in sheep. 【Method】 Twenty wethers with an average live weight of 22.9 ± 0.8 kg were randomly divided into five groups and fed with the control diet which was supplied 0.3 mg Co/kg DM to the basal diet, and 4 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 weeks. The metabolism trial was conducted in the middle period of the feeding experiment. The blood samples were collected at 2-week intervals. Vitamin B12 and folate concentrations were analyzed using electrochemistry luminescence method. Plasma methylmalonic acid was analyzed by a modified GC method. Plasma level of homocysteine was analyzed by fluorescence immunoassay.【Result】 Supplementation of Co and Cu at different levels improved plasma vitamin B12 concentration which was increased with feeding time, but stable after 6 weeks. Vitamin B12 status was accounted for by Co intake with no collaborate 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 effects. Addition of Co and Cu at different levels had no influence on digestibility of DM, OM, CP and NFE and N metabolism (P＞0.05), but the digestibility of fat and fibre (P＜0.01) was enhanced by supplementation of appropriate levels of 0.3 mg?kg-1 DM of Co and 20 mg?kg-1 DM of Cu. 【Conclusion】 In conclusion, supplementation of Co and Cu at different levels has no influence on vitamin B12 status. The optimum ratio of Co and Cu in diet could enhance the nutrient utilization.

Key words: cobalt, vitamin B12, sheep, nutrient utilization