硝态氮在绵羊瘤胃中的代谢途径初探

A preliminary investigation of metabolic pathway of nitrate in rumen of sheep

本研究旨在通过产气量法研究绵羊适应硝酸盐前后硝态氮(NO3--N)在瘤胃中的代谢途径。试验采用单因素完全随机设计,6只饲喂硝态氮日粮(试验组)和尿素氮日粮(对照组)的绵羊作为瘤胃液的供体。硝态氮在发酵底物中的含量为2%(干物质基础)。结果表明,硝态氮经来自于尿素氮日粮的微生物发酵(24 h),NO3--N、亚硝态氮(NO2--N)、氨态氮(NH3-N)和微生物氮(MN)分别占发酵底物总氮的0.2%、0%、80%和15%;硝态氮经来自于硝态氮日粮的微生物发酵(24 h),NO3--N、NO2--N、NH3-N和MN分别占发酵底物总氮的0%、0%、32.8%和52.2%,对照组和试验组硝态氮的主要还原产物均为NH3-N和MN,其中未检测到一氧化二氮(N2O),仅检测到有少量氮气(N2)产生,表明对照组和试验组的瘤胃微生物对硝态氮的代谢均以异化还原为主,并可能存在一定的反硝化作用。

The test was conducted in a completely randomized factorial design to study metabolic pathway of nitrate in the rumen by an in vitro gas production method.Rumen microbes were obtained from 6 sheep fed with a urea（UR）diet and a nitrate （NI）diet.The concentration of nitrate-N was 2% in fermentation substrates.The results showed that：after fermentation for 24 h,the concentrations of NO3-N, NO2-N,NH3-N and microbial nitrogen （MN） with microbial source from urea diet-fed sheep were 0.2%,0%, 80% and 15% in total nitrogen of the fermentation substrates.Similarly, the concentra- tions of NO3-N,NO2-N,NH3-N and MN with microbial source from nitrate diet-fed sheep were 0% ,0% ,32.8% and 52.2% in total nitrogen of the fermentation substrates.The main reduction product of nitrate was the NH3-N and MN.Nitrous oxide （N20）was not detected. Only small amount of nitrogen （N2）was found.It indicated that dissimilatory reduction was the main metabolic pathway of nitrate in the rumen regardless of microbial source from UR diet-fed sheep or UR diet-fed sheep.Maybe there was denitrification of nitrate in the rumen.