进行这项研究以比较瘤胃保护(RP-Leu)和未保护的L-亮氨酸(RU-Leu)对发酵参数的影响。细菌组成,体外瘤胃分批孵育和氨基酸代谢。将5.00gRP-Leu或RU-Leu产品在4头肉牛(Bostaurus)的瘤胃中原位孵育,并在0、2、4、6、12、16和24h后取出,以确定瘤胃保护率。在体外孵育中,RP-Leu和RU-Leu均补充1.5mmol/瓶(L-亮氨酸HCl),并在0、2、4、6、8、12和16小时后孵育以测量气体产量(GP),养分降解性,发酵参数,细菌组成,和氨基酸代谢。体外实验和原位实验的结果证实,RP-Leu的瘤胃保护率高于RU-Leu(p<0.01),而后者在孵育8小时内降解缓慢(p<0.05)。来自RP-Leu和RU-Leu的游离亮氨酸在孵育6小时时达到峰值(p<0.01)。RU-Leu补充增加了(p<0.05)产气量,微生物粗蛋白,支链AA,丙酸和支链VFA浓度,与对照和RP-Leu补充剂相比,Shannon和Sobs指数。RU-Leu和RP-Leu补充降低了(p<0.05)拟杆菌的相对丰度,Firmicutes增加(p<0.05)。相关分析表明,在属水平上有5种细菌可能与MCP和丙酸盐呈正相关(p<0.05)。根据结果,我们发现RP-Leu比RU-Leu在瘤胃液中更稳定,但是RU-Leu在短时间内也不会被瘤胃微生物迅速降解。RU-Leu在调节瘤胃发酵模式方面更有益,微生物粗蛋白合成,在体外瘤胃条件下,支链VFA的产量比RP-Leu高。
This study was conducted to compare the effects of rumen-protected (RP-Leu) and unprotected L-leucine (RU-Leu) on the fermentation parameters, bacterial composition, and amino acid metabolism in vitro rumen batch incubation. The 5.00 g RP-Leu or RU-Leu products were incubated in situ in the rumen of four beef cattle (Bos taurus) and removed after 0, 2, 4, 6, 12, 16, and 24 h to determine the rumen protection rate. In in vitro incubation, both RP-Leu and RU-Leu were supplemented 1.5 mmol/bottle (L-leucine HCl), and incubated after 0, 2, 4, 6, 8, 12, and 16 h to measure gas production (GP), nutrient degradability, fermentation parameters, bacterial composition, and amino acids metabolism. Results from both in vitro and in situ experiments confirmed that the rumen protection rate was greater (p < 0.01) in RP-Leu than in RU-Leu, whereas the latter was slow (p < 0.05) degraded within incubation 8 h. Free leucine from RP-Leu and RU-Leu reached a peak at incubation 6 h (p < 0.01). RU-Leu supplementation increased (p < 0.05) gas production, microbial crude protein, branched-chain AAs, propionate and branched-chain VFAs concentrations, and Shannon and Sobs index in comparison to the control and RP-Leu supplementation. RU-Leu and RP-Leu supplementation decreased (p < 0.05) the relative abundance of Bacteroidota, which Firmicutes increased (p < 0.05). Correlation analysis indicated that there are 5 bacteria at the genus level that may be positively correlated with MCP and propionate (p < 0.05). Based on the result, we found that RP-Leu was more stable than RU-Leu in rumen fluid, but RU-Leu also does not exhibit rapid degradation by ruminal microbes for a short time. The RU-Leu was more beneficial in terms of regulating rumen fermentation pattern, microbial crude protein synthesis, and branched-chain VFAs production than RP-Leu in vitro rumen conditions.