This study aimed to evaluate the effect of dietary humic acid (HA) supplementation on the growth performance, nutrient digestibility, carcass characteristics, blood metabolites, and caecal fermentation activity in growing rabbits. Six-week-old New Zealand White (NZW) rabbits (n = 63) with an initial body weight of 726.32 ± 42.85 g, were randomly allocated to three groups of 21 rabbits each. Rabbits were fed on the basal diet with 0 (HA0, control), 5 (HA5) and 10 (HA10) gram/kilogram diet for 70 days in a completely randomised experimental design. A significant heavier (P < 0.001) final body weight and a higher average daily gain, with lower feed intake, and a better feed conversion ratio were in HA5 and HA10 rabbits. The digestibility of HA-supplemented diets was greater than that of HA0. Heaviest carcass weights (P < 0.05) were observed in the HA5 rabbits, followed by the HA10 rabbits vs. HA0. Protein and ash content of meat increased (P < 0.001) in all HA rabbits, while the ether extract decreased (P < 0. 01) in HA5 and HA10 rabbits. The HA-treated rabbits were distinguished by increased (P < 0.001) total protein, albumin, and globulin levels. However, the total cholesterol, triglycerides, and urea levels decreased (P < 0.001), and the blood glucose and creatinine levels remained unaffected with HA supplementation. Addition of HA reduced the pH of caecum and sharply decreased (P < 0.001) NH₃-N content but it had no significant effect on the levels of total volatile fatty acids and acetic acid. Levels of propionic and butyric acid increased (P < 0.001) in response to HA supplementation. In conclusion, supplementation of HA of up to 10 g/kg can be used in diets of growing rabbits, with significant effects on the digestion, growth performance, blood cholesterol concentration, and caecal fermentation activity.

Graphic Abstract

中文翻译：

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兔饲料中提取和表征的腐殖质作为饲料补充剂：对性能，血液代谢产物和盲肠发酵活性的影响

这项研究旨在评估日粮添加腐殖酸（HA）对家兔生长性能，养分消化率，car体特性，血液代谢产物和盲肠发酵活性的影响。将六周大的新西兰白（NZW）兔（n = 63）初始体重为726.32±42.85 g，随机分为三组，每组21只。在完全随机的实验设计中，以0（HA0，对照），5（HA5）和10（HA10）克/千克的基础饲料喂养兔子70天。重得多（P （<0.001）的最终体重和较高的平均日增重，较低的采食量和较高的饲料转化率在HA5和HA10兔子中。补充HA的饮食的消化率高于HA0。在HA5 兔中观察到最重的cas体重量（P <0.05），其次是HA10兔vs.HA0。 在所有HA兔中，肉中蛋白质和灰分的含量均增加（P <0.001），而 在HA5和HA10兔中，乙醚提取物的含量下降（P <0. 01）。经HA治疗的兔的 总蛋白，白蛋白和球蛋白水平升高（P <0.001），从而与众不同。但是，总胆固醇，甘油三酸酯和尿素水平降低了（P <0.001），并且补充HA不会影响血糖和肌酐水平。添加HA降低了盲肠的pH值，并急剧降低了（P  <0.001）NH ₃ -N含量，但对总挥发性脂肪酸和乙酸的含量没有显着影响。 补充HA后，丙酸和丁酸水平增加（P <0.001）。总之，在生长中的家兔的日粮中可添加高达10 g / kg的HA，这对消化，生长性能，血胆固醇浓度和盲肠发酵活性具有显着影响。

图形摘要