Tadpole cultivation is a crucial step in the artificial production of bullfrogs (), but its feed nutrition is poorly understood. This study examined how dietary lipid and protein levels affect metamorphosis, growth and intestinal health of tadpole. Six groups of tadpoles were fed six diets with two lipid levels (7% and 10%) and three protein levels (36%, 40% and 44%) for 70 days. The results showed that at 7% lipid level, increasing protein enhanced metamorphosis rate and mean weight of tadpoles, reaching the optimal value at 40% protein ( < 0.05). At 10% lipid level, increasing protein also improved mean weight, peaking at 40% protein. Dietary nutrition also influenced liver amino acid and lipid metabolism directly. At 7% lipid level, increasing protein significantly increased the activities of hepatic enzymes GLS, PDH, ALT, AST, etc. ( < 0.05), and up-regulated the expression of hepatic genes , , and involved in lipid metabolism ( < 0.05). At 10% lipid level, increasing protein also up-regulated and genes ( < 0.05), but down-regulated gene. Meanwhile, increasing dietary lipid level elevated TG and T-CHO levels in liver. Increasing dietary protein enhanced gut microbiota richness, while increasing lipid reduced it. Moreover, different gut microbiota groups had distinct biomarkers, such as , , and Bacteroidales, which were related to amino acid or lipid metabolism. In summary, under the test conditions, 7% lipid and 40% protein in diet are suitable levels, which can promote metamorphosis, growth and metabolism of tadpoles, and are more economical than high-lipid and high-protein diets.

中文翻译：

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膳食脂质和蛋白质水平对蝌蚪变态、生长、代谢和肠道微生物群的影响

蝌蚪培育是人工生产牛蛙的关键步骤，但其饲料营养却知之甚少。这项研究探讨了膳食脂质和蛋白质水平如何影响蝌蚪的变态、生长和肠道健康。六组蝌蚪被喂食六种饮食，分别具有两种脂质水平（7%和10%）和三种蛋白质水平（36%、40%和44%），持续70天。结果表明，在7%脂质水平下，增加蛋白质可提高蝌蚪变态率和平均体重，在40%蛋白质时达到最佳值（<0.05）。在 10% 的脂质水平下，增加蛋白质也可以改善平均体重，在蛋白质含量达到 40% 时达到峰值。膳食营养还直接影响肝脏氨基酸和脂质代谢。在7%血脂水平下，增加蛋白质显着提高肝酶GLS、PDH、ALT、AST等的活性（<0.05），并上调参与脂质代谢的肝基因表达（<0.05） 。在10%脂质水平下，增加蛋白质也上调基因(<0.05)，但下调基因。同时，增加膳食脂质水平会升高肝脏中的 TG 和 T-CHO 水平。增加膳食蛋白质可以增强肠道微生物群的丰富度，而增加脂质则可以减少肠道微生物群的丰富度。此外，不同的肠道微生物群具有不同的生物标志物，例如与氨基酸或脂质代谢相关的细菌目、细菌目和拟杆菌目。综上所述，在试验条件下，日粮中7%的脂质和40%的蛋白质是适宜的水平，能够促进蝌蚪的变态、生长和代谢，且比高脂、高蛋白日粮更为经济。