This study was aimed to estimate the effect of soy lecithin (SL) on growth performance, serum metabolites, rumen fermentation and microbial flora in Simmental steers. Sixty Simmental steers were randomly assigned to four treatments: control (C), S1 (TMR with 10 g/kg (DM) SL), S2 (TMR with 20 g/kg (DM) SL) and S3 (TMR with 40 g/kg (DM) SL).The ADG of steers fed 10 g/kg, 20 g/kg and 40 g/kg SL was 8.6%, 22.5% and 9.4% higher than that control group, respectively (P<0.001), while FCR decreased quadratically (P<0.001) by increasing the SL level, and the lowest FCR was achieved for steers fed 20 g/kg SL. There was a linear decrease in the ruminal pH value yet a quadratic increase in acetate and total VFAs concentration by increasing the SL supplementation (P<0.001). The serum concentrations of CHO, TG, HDL, FAS and HLS concentrations showed a linear increase by increasing the SL supplementation (P<0.05). The rumen bacterial community of five phyla (Bacteroidetes, Firmicutes, Proteobacteria, Spirochaetae and Actinobacteria) and genera (Prevotella, Bacteroidales_BS11_gut, Prevotellaceae_UGG-033, Rikenellacese_RC and Coprostanoligenes) that were most abundant in the rumen microbial flora was not affected by SL supplementation (P>0.05), while some ruminal bacterial with lower abundance showed a linear decrease by increasing the SL supplementation. Therefore, SL supplementation improved growth performance and increased ruminal VFA yields of Simmental steers with no inhibitory effect on the dominant ruminal bacterial. Based on the results of growth performance, the recommended amount of SL supplement is 20 g/kg DM for beef steers.

这项研究旨在评估大豆卵磷脂（SL）对西门塔尔牛的生长性能，血清代谢产物，瘤胃发酵和微生物菌群的影响。将60只西门塔尔牛ers牛随机分配给四种处理方法：对照（C），S1（TMR含10 g / kg（DM）SL），S2（TMR含20 g / kg（DM）SL）和S3（TMR含40 g / kg（DM）SL）。饲喂10 g / kg，20 g / kg和40 g / kg SL的ste牛的ADG分别比对照组高8.​​6％，22.5％和9.4％（P <0.001），而通过增加SL水平，FCR呈二次下降趋势（P <0.001），而饲喂20 g / kg SL的公牛的FCR最低。瘤胃pH值呈线性下降，而乙酸盐和总VFA浓度通过增加SL补充量呈二次增加（P<0.001）。血清中CHO，TG，HDL，FAS和HLS的浓度通过增加SL的添加呈线性增加（P <0.05）。5个门类的瘤胃细菌群落（拟杆菌，厚壁菌门，变形菌，Spirochaetae和放线菌）及属（普氏菌，Bacteroidales_BS11_gut，Prevotellaceae_UGG-033，Rikenellacese_RC和Coprostanoligenes），其是最丰富的瘤胃微生物菌群并没有受到SL补充（P> 0.05），而一些较低丰度的瘤胃细菌通过增加SL的添加呈线性下降。因此，SL补充剂改善了西门塔尔ste牛的生长性能并提高了瘤胃VFA产量，而对主要瘤胃细菌没有抑制作用。根据生长性能的结果，推荐用于牛肉的SL补充剂的量为20 g / kg DM。