添加支链氨基酸或支链脂肪酸对玉米秸秆体外瘤胃发酵和细菌多样性的影响

Effects of Branched Chain Amino Acids or Fatty Acid Supplementation on in Vitro Fermentation of Corn Straw and Bacterial Diversity

采用体外培养技术,研究了添加2mmol/L或4mmol/L支链氨基酸(branched-chain amino acid,BCAA)或支链脂肪酸(branched-chain volatile fatty acid,BCVFA)对玉米秸秆72h体外发酵的影响。结果表明,添加2mmol/L BCVFA或BCAA对总挥发性脂肪酸(TVFA)、乙酸、丙酸、丁酸、干物质(DM)和中性洗涤纤维(NDF)降解率均无显著影响。与BCVFA相比,添加相应BCAA均有升高TVFA的趋势。添加缬氨酸(Val)和异丁酸使异丁酸浓度较对照组增加2.85倍和3.12倍(P<0.05);添加亮氨酸(Leu)、异戊酸、异亮氨酸(Ile)和2-甲基丁酸后,异戊酸浓度增加2.20～2.50倍(P<0.05)。与相应BCVFA相比,Val、Leu和Ile使戊酸浓度分别增加27.69%(P<0.05),25.68%(P<0.05)和39.34%(P<0.05)。添加4mmol/L BCAA或BCVFA均导致发酵末期pH值下降,玉米秸秆的DM和NDF降解率显著增加,TVFA、乙酸、丙酸和丁酸有增加的趋势。添加异戊酸、Ile和2-甲基丁酸后丙酸水平增加29.94%(P<0.05),26.31%(P<0.05)和25.00%(P<0.05)。添加Val和异丁酸后异丁酸增加5.30倍和5.45倍(P<0.05)。添加Leu、异戊酸、Ile或2-甲基丁酸使异戊酸水平增加3.76～4.20倍(P<0.05)。与相应BCVFA相比,Val、Leu和Ile使戊酸浓度分别增加22.92%(P<0.05),33.33%(P<0.05)和55.00%(P<0.05)。PCR-DGGE结果显示,添加4mmol/L的BCAA或BCVFA明显改变瘤胃细菌多样性指数。以玉米秸秆为发酵底物时,BCAA或BCVFA的添加水平以4mmol/L较好,其中Val优于异丁酸,而Leu和异戊酸之间以及Ile和2-甲基丁酸之间无显著差异。

In vitro culture technique was adopted to study the effects of branched-chain amino acid （BCAA） or branched-chain volatile fatty acid （BCVFA） on fermentation of corn straw. Results showed that the concentration of total volatile fatty acid, acetic acid, propanoic acid, and butyric acid, and the degra- dation of dry matter （DM） and neutral detergent fiber （NDF） were not affected by 2 mmol/L BCAA or BCVFA supplementation. Compared with the BCVFA,BCAA supplementation tended to increase the con- centrations of total volatile fatty acid （TVFA）. Supplementation of valine （Val） and isobutyric acid in- creased the concentrations of isobutyric acid in the ruminal fluid by 2.85 and 3.12 fold （ P 〈0.05）. Addi tion of leucine （Leu）,isovaleric acid,isoleucine （Ile） and 2-methylbutyric acid increased the concentration of isovaleric acid in the ruminal fluid by 2.20-2.50 fold （ P 〈0.05）. Compared with the BCVFA,supple- mentation of Val,I.eu and Ile increased the concentration of valeric acid in ruminal fluid by 27.69~/oo （ P0.05） ,25.68~//oo （ P %0.05） and 39.34% （ P %0.05） respectively. Final pH decreased and degradation of DM and NDF of corn straw increased and the concentrations of TVFA,acetic acid, propanoic acid and bu- tyric acid tended to increase by 4 mmol/L BCAA or BCVFA supplementation. Addition of isovaleric acid, Ile and 2-methylbutyric acid increased the concentrations of propanoic acid by 29. 94% （ P %0. 05）,26.31%0 （ P %0.05） and 25. creased the concentrations of tion of 4 mmol/L Leu,isoval acid in the ruminal fluid by 3 00% （ P 〈0.05） isobutyric acid in respectively. Supplementation of Val and isobutyric acid in- the ruminal fluid by 5.30 and 5.45 fold （ P 〈0.05）. Addi- eric acid,Ile and 2-methylbutyric acid increased the concentration of isovaleric acid in the ruminal fluid by 3.76-4.20 fold （ P〈0.05）. Compared with the BCVFA,supplementation of4 mmol/L Val,Leu and Ile increased the concentration of valeric acid in ruminal fluid by 22.92% （ P 〈 0.05） ,33.33% （ P 〈0.05） and 55.00% （ P 〈0.05） respectively. The results of PCR-DGGE revealed that the ruminal bacterial diversity index was obviously changed by BCAA or BCVFA addition at the concentra- tion of 4 mmol/L. These results implied that when corn straw was used as fermentation substrate,4 mmol/L was considered better suppliment for BCAA or BCFA. The effects of Val is better than that of isobutyric acid. There is insignificant difference between Leu and isovaleric acid,and Ile and 2-methylbutyrie acid.