植物精油对尿素氮在瘤胃内容物中分布的影响

【目的】揭示尿素氮在奶牛瘤胃内容物中的分布特点，阐明精油对尿素氮分布和瘤胃发酵的影响。【方法】在含瘤胃液和15N尿素的发酵瓶中，加入终浓度为300 mg?L-1大蒜精油、茶树精油和尤加利精油，发酵后检测微生物中15N的丰度和瘤胃发酵指标，并利用DGGE刻画细菌群落变化。【结果】随着发酵时间的增加，瘤胃液中的尿素氮逐渐降低，而瘤胃固相和液相微生物中的尿素氮逐渐升高，发酵24 h 三者中的尿素氮基本持平。发酵24 h时，与空白对照组相比，大蒜精油处理组瘤胃固相和液相微生物尿素氮丰度分别降低了22.60%和18.75%，发酵液pH和氨氮浓度分别降低了3.02%和17.80%，异丁酸和乙酸/丙酸值有所升高。茶树精油和尤加利精油则显著降低了发酵液pH（P＜0.05），提高了异丁酸和乙酸/丙酸值。DGGE图谱显示，发酵24 h时，3种植物精油可改变瘤胃细菌的群落结构。【结论】瘤胃尿素氮逐渐由瘤胃液向微生物中富集，大蒜精油可减缓尿素氮富集速度，改变细菌群落的组成，抑制氨氮生成。

Effect of Plant Essential Oil on the Distribution of Urea-Nitrogen in Rumen Contents

【Objective】The objective of the experiment is to reveal the distribution of urea-nitrogen in rumen contents and the effect of essential oil on the distribution.【Method】Garlic oil,tea tree oil and eucalyptus oils were added into serum bottles containing rumen fluid and1 5N-urea.The abundance of 15N and rumen fermentation were detected after incubation.The bacterial population was studied by DGGE.【Result】Urea nitrogen in rumen fluid decreased and that in the microbes associated with rumen solid and liquid phases increased following the incubation time,and then had the similar level at 24 h.Compared to the control,urea nitrogen abundance in the microbes associated with rumen solid and liquid phases treated with garlic oil increased by 22.60% and 18.75%,pH and ammonia nitrogen decreased by 3.02% and 17.80%,respectively.The proportion of isobutyric acid and acetic acid:propionic acid increased at 24 h.The pH in rumen fluid treated with tea tree and eucalyptus oils decreased(P<0.05),and the proportion of isobutyric acid and acetic acid:propionic acid increased.Three different essential oils affected bacterial population according to the results by DGGE.【Conclusion】Urea-nitrogen was transferred from rumen fluid to microbes,and garlic oil inhibited the transfer, changed microbial population and decreased ammonia production.