The energy/protein imbalance in a low-protein diet induces lipid metabolism disorders in late-phase laying hens. Reducing energy levels in the low-protein diet to adjust the energy-to-protein ratio may improve fat deposition, but this also decreases the laying performance of hens. This study investigated the mechanism by which different energy levels in the low-protein diet influences liver lipid metabolism in late-phase laying hens through the enterohepatic axis to guide feed optimization and nutrition strategies. A total of 288 laying hens were randomly allocated to the normal-energy and normal-protein diet group (positive control: CK) or 1 of 3 groups: low-energy and low-protein diet (LL), normal-energy and low-protein diet (NL), and high-energy and low-protein diet (HL) groups. The energy-to-protein ratios of the CK, LL, NL, and HL diets were 0.67, 0.74, 0.77, and 0.80, respectively. Compared with the CK group, egg quality deteriorated with increasing energy intake in late-phase laying hens fed low-protein diet. Hens fed LL, NL, and HL diets had significantly higher triglyceride, total cholesterol, acetyl-CoA carboxylase, and fatty acid synthase levels, but significantly lower hepatic lipase levels compared with the CK group. Liver transcriptome sequencing revealed that genes involved in fatty acid beta-oxidation (ACOX1, HADHA, EHHADH, and ACAA1) were downregulated, whereas genes related to fatty acid synthesis (SCD, FASN, and ACACA) were upregulated in LL group compared with the CK group. Comparison of the cecal microbiome showed that in hens fed an LL diet, Lactobacillus and Desulfovibrio were enriched, whereas riboflavin metabolism was suppressed. Cecal metabolites that were most significantly affected by the LL diet included several vitamins, such as riboflavin (vitamin B2), pantethine (vitamin B5 derivative), pyridoxine (vitamin B6), and 4-pyridoxic acid. A lipid metabolism disorder due to deficiencies of vitamin B2 and pantethine originating from the metabolism of the cecal microbiome may be the underlying reason for fat accumulation in the liver of late-phase laying hens fed an LL diet. Based on the present study, we propose that targeting vitamin B2 and pantethine (vitamin B5 derivative) might be an effective strategy for improving lipid metabolism in late-phase laying hens fed a low-protein diet.

中文翻译：

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低蛋白日粮不同能量水平通过肠肝轴对后期蛋鸡肝脏脂质代谢的影响


低蛋白日粮中的能量/蛋白质失衡会引起后期产蛋鸡的脂质代谢紊乱。降低低蛋白日粮中的能量水平以调整能量与蛋白质的比例可能会改善脂肪沉积，但这也会降低母鸡的产蛋性能。本研究探讨了低蛋白日粮中不同能量水平通过肠肝轴影响后期蛋鸡肝脏脂质代谢的机制，以指导饲料优化和营养策略。总共 288 只蛋鸡被随机分配到正常能量和正常蛋白质饮食组（阳性对照：CK）或 3 组中的一组：低能量和低蛋白质饮食（LL）、正常能量和低蛋白质饮食组。蛋白质饮食（NL）组和高能量低蛋白质饮食（HL）组。 CK、LL、NL 和 HL 日粮的能量与蛋白质比率分别为 0.67、0.74、0.77 和 0.80。与CK组相比，饲喂低蛋白日粮的后期产蛋鸡随着能量摄入的增加，蛋品质下降。与CK组相比，饲喂LL、NL和HL日粮的母鸡甘油三酯、总胆固醇、乙酰辅酶A羧化酶和脂肪酸合酶水平显着升高，但肝脂肪酶水平显着降低。肝脏转录组测序显示，与 CK 组相比，LL 组参与脂肪酸 β-氧化的基因（ACOX1、HADHA、EHHADH 和 ACAA1）下调，而与脂肪酸合成相关的基因（SCD、FASN 和 ACACA）上调团体。盲肠微生物群的比较表明，在饲喂 LL 日粮的母鸡中，乳酸菌和脱硫弧菌丰富，而核黄素代谢受到抑制。 受 LL 饮食影响最显着的盲肠代谢物包括多种维生素，如核黄素（维生素 B2）、泛硫乙胺（维生素 B5 衍生物）、吡哆醇（维生素 B6）和 4-吡哆酸。由于盲肠微生物代谢引起的维生素 B2 和泛硫乙胺缺乏而导致的脂质代谢紊乱可能是饲喂 LL 日粮的后期产蛋鸡肝脏脂肪堆积的根本原因。根据目前的研究，我们提出，以维生素 B2 和泛硫乙胺（维生素 B5 衍生物）为目标可能是改善低蛋白日粮后期产蛋鸡脂质代谢的有效策略。