Table_3_Dietary Energy Levels Affect Carbohydrate Metabolism-Related Bacteria and Improve Meat Quality in the Longissimus Thoracis Muscle of Yak (Bos grunniens).DOCX

The effects of different dietary energy levels on the ruminal bacterial population, selected meat quality indices, and their relationship in yak longissimus thoracis (LT) muscle were assessed in this study. A total of 15 castrated yaks were randomly assigned to three groups with low- (NEg: 5.5 MJ/Kg, LE), medium- (NEg: 6.2 MJ/Kg, ME), and high- (NEg: 6.9 MJ/Kg, HE) dietary energy levels and occurred in the cold season (March to May). All yaks from each treatment group were humanely slaughtered and sampled on the day of completion of their feeding treatment. The results showed that the water content and crude fat levels of the LT muscle were markedly elevated in the HE group (P < 0.05), while the shear force was drastically reduced (P = 0.001). Methionine, aspartic acid, and glycine levels in the LT muscle were higher in the LE group compared with the ME and HE groups (P < 0.05). The glutamic acid level in the ME group was greater in comparison to the LE and HE groups (P < 0.05), while the histidine level in the ME group was higher than that in the HE group (P < 0.05). Additionally, the HE diet significantly elevated (P < 0.05) the abundance of carbohydrate metabolism-associated bacteria including Prevotella_1, Lachnospiraceae_NK4A136_group, U29_B03, Ruminiclostridium_6, and Ruminococcaceae_UCG_013 in the rumen. The results of the Spearman's rank correlation analysis showed that the abundance of uncultured_bacterium_f_vadinBE97 and uncultured_bacterium_f_Lachnospiraceae showed a significant influence on the indicator of IMF and SF. In conclusion, a high dietary energy level improved the meat quality in the LT muscle of yak mainly by increasing the relative abundance of ruminal amylolytic bacteria to provide substrates for fatty acid synthesis.

本研究旨在评估不同膳食能量水平对牦牛背最长肌（LT）肌内细菌群落、选定的肉质指标及其相互关系的影响。共选取15头阉割牦牛随机分为低能量组（NEg：5.5 MJ/Kg，LE）、中能量组（NEg：6.2 MJ/Kg，ME）和高能量组（NEg：6.9 MJ/Kg，HE），实验于寒冷季节（3月至5月）进行。每个处理组的牦牛均在完成喂养治疗后进行人道屠宰并取样。研究结果显示，高能量组（HE组）的LT肌水分含量和粗脂肪水平显著升高（P < 0.05），而剪切力则显著降低（P = 0.001）。与中能量组（ME组）和高能量组（HE组）相比，低能量组（LE组）的LT肌中蛋氨酸、天冬氨酸和甘氨酸水平较高（P < 0.05）。与低能量组（LE组）和高能量组（HE组）相比，中能量组（ME组）的谷氨酸水平较高（P < 0.05），而组氨酸水平在中能量组（ME组）中高于高能量组（HE组）（P < 0.05）。此外，高能量膳食显著增加了瘤胃中碳水化合物代谢相关细菌的丰度，包括Prevotella_1、Lachnospiraceae_NK4A136_group、U29_B03、Ruminiclostridium_6和Ruminococcaceae_UCG_013等（P < 0.05）。Spearman等级相关分析结果显示，未培养细菌f_vadinBE97和未培养细菌f_Lachnospiraceae的丰度对IMF和SF指标具有显著影响。总之，高膳食能量水平主要通过增加瘤胃中淀粉酶细菌的相对丰度，为其提供脂肪酸合成的底物，从而提高牦牛LT肌的肉质。