日粮钴铜比例对肉用绵羊维生素B_(12)营养状况及养分代谢的影响

Influence of Cobalt and Copper Supplementation on Vitamin B_(12) Status and Nutrient Utilization in Sheep

【目的】研究不同比例的日粮钴铜对肉用绵羊维生素B12营养状况及营养物质消化代谢的影响。【方法】选取20只健康、体重相近(22.9±0.8)kg的小尾寒羊×无角陶赛特杂交一代羯羊,随机分为5组,定量饲喂5种不同日粮,即对照组日粮、4种不同比例的钴铜(0.3:10、0.3:20、0.6:10和0.6:20)日粮,试验期8周,试验中期进行消化代谢试验,同时每两周采血样,用电化学发光法、气相色谱法及荧光偏振免疫法测定血浆维生素B12及叶酸含量、甲基丙二酸和同型半胱胺含量。【结果】肉羊日粮添加不同比例的钴铜,血液维生素B12的含量随饲喂时间的延长而增加,6周后趋于稳定。钴水平较高的后两组显著高于其它3组(P<0.01),血液维生素B12含量主要取决于钴的摄入量,钴和铜无协同效应。血浆甲基丙二酸和血糖含量随日粮钴铜比例增加而呈下降和上升趋势,同型半胱胺水平无变化,叶酸含量在0.6:20mg·kg-1钴铜添加组显著升高(P<0.05)。钴和铜的添加比例对DM、OM、CP、NFE表观消化率及氮代谢无影响(P>0.05),而配比为0.3:20时显著促进脂肪和纤维的消化(P<0.01)。【结论】肉羊日粮中钴和铜的添加比例对维生素B12营养状况无影响,但适宜配比有利于营养物质的消化代谢。

[Objective] The experiment was carried out to study the effects of different cobalt （Co） and copper （Cu） supplementation on vitamin Bla 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 0.6mg·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 B 12 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 20mg·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.