稻草或玉米秸秆替代苜蓿对奶牛氮代谢、血清生理生化指标及肝脏和肾脏组织形态变化的影响

Effects of Alfalfa Replacement by Rice Straw or Corn Stover on Nitrogen Metabolism,Serum Physiological-Biochemical Indices and Histomorphology of Liver and Kidney of Dairy Cows

本试验旨在研究稻草或玉米秸秆替代苜蓿对奶牛氮代谢、血清生理生化指标及肝脏和肾脏组织形态变化的影响。选择45头泌乳中期的经产健康荷斯坦奶牛,随机分成3组,每组15头牛。各组饲喂含不同粗饲料的饲粮,分别为苜蓿组(23%苜蓿干草+7%羊草,AH组)、玉米秸秆组(30%玉米秸秆,CS组)和稻草组(30%稻草,RS组),饲粮精粗比均为55∶45。试验期12周。结果表明:CS组和RS组奶牛的粪氮排泄量显著高于AH组(P<0.05),RS组奶牛的尿氮排泄量显著高于AH组和CS组(P<0.05)。RS组奶牛的血清尿素氮和肌酸酐含量显著高于AH组(P<0.05)。RS组奶牛的血清总胆固醇含量显著高于AH组和CS组(P<0.05)。CS组奶牛的血清谷丙转氨酶活性显著高于AH组(P<0.05),而血清谷草转氨酶活性显著高于AH组和RS组(P<0.05)。各组奶牛的肝脏、肾脏组织切片结构清晰,未见明显异常。由此可见,饲喂玉米秸秆或稻草粗饲料的奶牛粪氮、尿氮排泄量的增加导致奶牛氮的利用效率降低。各组奶牛肝脏和肾脏的组织形态无显著变化,但饲喂玉米秸秆或稻草饲粮可导致奶牛血清中反映肝脏、肾脏健康功能的指标升高。

The aim of this study was to investigate the effects of alfalfa replacement by rice straw or corn stover on nitrogen metabolism, serum physiological-biochemical indices and histomorphology of liver and kidney of dairy cows. Forty-five multiparous Holstein dairy cows were blocked and randomly assigned to 3 groups with 15 cows per group. Cows in the 3 groups were fed with different roughages： alfalfa group （23% alfalfa hay and 7% Chinese wild rye hay, AH group）, corn stover group （30% corn stover, CS group） and rice straw group （30% rice straw, RS group）, dietary forage to concentrate ratio was 55：45. The experiment lasted for 12 weeks. The results showed that the fecal nitrogen excretion of cows in CS group and RS group was significanly higher than that in AH group （P〈0.05）, the urinary nitrogen excretion of cows in RS group was significanly higher than that in AH group and CS group （P〈0.05）. The serum urea nitrogen and creatinine contents of cows in RS group were significanly higher than those in AH group （P〈0.05）. The serum total cholesterol content in RS group was significanly higher than that in AH group and CS group （P〈0.05）. The serum alanine aminotransferase activity in CS group was significanly higher than that in AH （P〈0.05）, while the serum glutamic oxaloacetic transaminase activity was significanly higher than that in AH group and RS group （ P〈0.05）. The histological structure of liver and kidney in each group was clear, and no obvious abnormality was found. From above, the greater excretion of fecal nitrogen and urinary nitrogen of cows fed rice straw or corn stover resulte lower nitrogen conversion efficiency to milk protein of cows. No apparent morphological changes in liver and kidney are observed. However, the serum indexes responding the healthy function of liver and kidney are increased when cows fed with corn stover or rice straw.