不同钴水平对肉用绵羊瘤胃维生素B_(12)合成、瘤胃发酵及造血机能的影响

Effects of Dietary Cobalts on Vitamin B_(12) Synthesis,Rumen Fermentation and Blood Parameters of Sheep

本试验研究不同钴水平对肉羊维生素B12的合成、瘤胃发酵及造血机能的影响。20只健康、体重相近（2 7.3±0.9）kg的杂交一代羯羊，平均分为5组，分别饲喂基础日粮（含钴0.0 8 6 mg/kg）、基础日粮中添加0.2 5、0.5 0、0.7 5和1.00 mg/kg钴的试验组日粮，饲粮进食量相同，试验期8周。结果表明，基础日粮中0.086 mg/kg的钴不能满足肉羊的需要，添加0.25～1.00 mg/kg钴，可促进瘤胃维生素B12的合成，其合成量随饲喂时间的延长而增加，6周后趋于稳定，第6、8周的平均值为31.70～44.83 nmol/L，钴的添加量低于0.50 mg/kg时瘤胃维生素B12的含量增加较快，超过该量增加的幅度延缓。添加0.50 mg/kg的钴可显著增加瘤胃总挥发性脂肪酸的产生量并使其中丙酸比例增加、异丁酸和异戊酸比例降低。添加0.25 mg/kg的钴即可维持正常的造血功能。建议肉羊日粮中钴的适宜添加水平为0.25～0.50 mg/kg（即适宜日粮钴水平为0.336～0.586 mg/kg）。

To evaluate the effects of different inclusion levels of dietary cobalt on vitamin B12 synthesis, rumen fermentation and blood parameters of sheep, twenty cannulated wethers with an average weight （27.3 ± 0.9） kg were randomly divided into five groups and fed diets supplemented with increasing levels of cobalt （0, 0.25, 0.50, 0.75 and 1.00 mg Co/kg DM） for 8 weeks. Results showed cobalt content of control diet （0.086 mg Co/kg DM） was inadequate for achieving optimal rumen fermentation and sustaining normal blood function. Supplementation of 0.25, 0.50, 0.75 and 1.00 mg Co/kg DM significantly （P〈0.05） improved rumen vitamin B12 concentration which was increased after feeding time, but being stable 6 weeks with the average values of 1.70, 40.96, 42.92 and 44.83 nmol/L at the end of 6 and 8 weeks of feeding respectively. Lambs supplemented with 0.50 mg Co/kg DM seemed to be beneficial for rumen total volatile fatty acid production and molar proportion of propionate, whereas iso-acids were impaired by Co supplementation. Supplemention of 0.25 mg Co/kg DM is enough to meet the requirement of sustaining normal blood function. Supplemention of Co for lambs is recommended to be 0.25 to 0.50 mg/kg DM （total diet Co is 0. 336-0. 586 mg/kg DM）.