硒对热应激条件下放牧绵羊瘤胃发酵及瘤胃微生物区系的影响

Effects of selenium on rumen fermentation and rumen microflora of grazing sheep under heat stress

为探讨热应激条件下补硒对放牧绵羊瘤胃发酵以及瘤胃微生物区系的影响,试验选择体重相近、健康的7~8月龄杜寒杂交羊10只,采用单因素完全随机试验设计,随机分成2组,每组5只。对照组不添加硒,试验组硒添加水平为0.2 mg/d(硒源为酵母硒)。在夏季温度最高的初伏到中伏期间,以自然放牧方式饲养20 d后,颈静脉采集血液测定血浆热休克蛋白70(HSP-70)含量,口腔采集瘤胃液测定瘤胃发酵相关指标,并分析瘤胃微生物区系的变化。结果表明:(1)与对照组相比,硒添加组绵羊血浆中HSP-70的水平显著降低(P<0.05)。(2)热应激条件下添加硒显著降低了瘤胃NH3-N浓度(P<0.05),对瘤胃总挥发性脂肪酸含量有提高趋势(P=0.10)。(3)主坐标分析表明,两组绵羊瘤胃菌群在OTU和属水平上均聚类于不同的坐标位置,具有明显的组间差异。硒添加组绵羊瘤胃中梭杆菌门、未排位的鼠杆菌科、奎因氏菌属、瘤胃球菌科UCG-010菌属、艰难杆菌属、毛螺菌科FE2018和AC2044菌群、未排位的克里斯滕森菌科以及FD2005、Family_XIII_AD3011_group、Caviibacter和Kandleria的相对丰度显著提高(P<0.05),而M2PT2-76_termite_group和假单胞菌属的相对丰度显著降低(P<0.05)。LEfSe分析表明,对照组中月形单胞菌属、假单胞菌属显著富集,硒添加组中梭杆菌门、奎因氏菌属、鼠杆菌科未排位的属、瘤胃球菌科UCG-004、UCG-005和UCG-010菌属、普雷沃氏菌科NK3B31菌群、毛螺菌科FE2018菌群以及艰难杆菌属显著富集。试验结果提示,补硒对放牧绵羊的热应激具有缓解作用,这种缓解作用与硒改变瘤胃微生物区系进而改变瘤胃发酵有关。

This experiment aimed to explore the effect of selenium(Se)supplementation on rumen fermentation and rumen microflora of grazing sheep under heat stress.Ten healthy Dorper×Thin-Tailed Han crossbred sheep(7~8 months old)with similar body weight were selected and randomly divided into 2 groups with 5 in each group,using single factor completely randomized trial design.One group was control group without Se supplementation,and another group was Se supplemental group(supplemental level:0.2 mg/d;selenium source:selenium yeast).After 20 days of natural grazing,the blood was collected from the jugular vein and the plasma was acquired to determine heat shock protein 70(HSP-70)content group.The rumen fluid was collected from the oral cavity to determine rumen fermentation-related indicators and analyzed the changes of rumen microflora.The results showed that:(1)Compared with control group,plasma HSP-70 level of sheep in Se supplemental group was significantly reduced(P<0.05).(2)The addition of Se under heat stress significantly reduced rumen NH_(3)-N concentration(P<0.05),and had a tendency to increase rumen total volatile fatty acids content(P=0.10).(3)The principal coordinate analysis showed that rumen microflora of the two groups of sheep clustered in different coordinate positions,and had obvious differences between groups at OTU and genus levels.Compared with control group,the relative abundance of Fusobacteria,norank_f_Muribaculaceae,Quinella,Ruminococcaceae_UCG-010,Mogibacterium,Lachnospiraceae_FE2018 and AC2044 group,norank_f_Christensenellaceae,FD2005,Family_XIII_AD3011_group,Caviibacter and Kandleria was significantly increased(P<0.05),while that of M2PT2-76_termite_group and Pseudomonas was significantly reduced(P<0.05).LEfSe analysis showed that Selenomonas_3 and Pseudomonas were enriched in control group,and Fusobacteria,Quinella,norank_f_Muribaculaceae,Ruminococcaceae_UCG-004,UCG-005 and UCG-010,Prevotellaceae_NK3B31_group,Lachnospiraceae_FE2018_group and Mogibacterium were enriched in Se supplemental group.The results indicated that selenium supplementation alleviated heat stress of grazing sheep,which related to the change of rumen microflora and the subsequent change of rumen fermentation in response to Se supplementation.