Betaine is widely used as a feed additive in the chicken industry to promote laying performance and growth performance, yet it is unknown whether betaine can be used in geese to improve the laying performance of goose breeders and the growth traits of offspring goslings. In this study, laying goose breeders at 39 weeks of age were fed basal (Control, CON) or betaine-supplemented diets at low (2.5 g/kg, LBT) or high (5 g/kg, HBT) levels for 7 weeks, and the breeder eggs laid in the last week were collected for incubation. Offspring goslings were examined at 35 d and 63 d of age. The laying rate tended to be increased (P = 0.065), and the feed efficiency of the breeders was improved by betaine supplementation, while the average daily gain of the offspring goslings was significantly increased (P < 0.05). Concentrations of insulin-like growth factor 2 (IGF-2) in serum and liver were significantly increased in the HBT group (P < 0.05), with age-dependent alterations of serum T3 levels. Concurrently, hepatic mRNA expression of the IGF gene family was significantly increased in goslings derived from betaine-treated breeders (P < 0.05). A higher ratio of proliferating cell nuclear antigen (PCNA)-immunopositive nuclei was found in the liver sections of the HBT group, which was confirmed by significantly upregulated hepatic expression of PCNA mRNA and protein (P < 0.05). Moreover, hepatic expression of thyroxine deiodinase type 1 (Dio1) and thyroid hormone receptor β (TRβ) was also significantly upregulated in goslings of the HBT group (P < 0.05). These changes were associated with significantly higher levels of global DNA 5-mC methylation, together with increased expression of methyl transfer genes (P < 0.05), including betaine-homocysteine methyltransferase (BHMT), glycine N-methyltransferase (GNMT) and DNA (cytosine-5-)-methyltransferase 1 (DNMT1). The promoter regions of IGF-2 genes, as well as the predicted TRβ binding site on the IGF-2 gene, were significantly hypomethylated (P < 0.05). These results indicate that gosling growth can be improved by dietary betaine supplementation in goose breeders via epigenetic modulation of the IGF gene family, especially IGF-2, in the liver.

中文翻译：

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亲代甜菜碱补充剂通过肝脏 IGF 基因家族的表观遗传调节促进小鹅生长

甜菜碱在养鸡业中​​被广泛用作饲料添加剂，以促进产蛋性能和生长性能，但甜菜碱是否可以用于鹅，以改善鹅种鸡的产蛋性能和子代雏鹅的生长性状尚不清楚。在这项研究中，39周龄的蛋鹅饲养者以低水平（2.5克/千克，LBT）或高水平（5克/千克，HBT）基础（对照，CON）或添加甜菜碱的日粮喂养7周，收集上周产下的种蛋进行孵化。子代小鹅在 35 天和 63 天时进行检查。补充甜菜碱可提高产蛋率（P=0.065），提高种鹅的饲料效率，同时显着提高子代鹅的平均日增重（P<0.05）。HBT组血清和肝脏中胰岛素样生长因子2（IGF-2）的浓度显着升高（P＜0.05），并且血清T3水平存在年龄依赖性变化。同时，在甜菜碱处理的种鹅中，IGF基因家族的肝脏mRNA表达显着增加（P＜0.05）。HBT组肝切片中增殖细胞核抗原（PCNA）免疫阳性细胞核比例较高，肝脏PCNA mRNA和蛋白表达显着上调（P＜0.05）。此外，HBT组雏鹅肝脏中甲状腺素脱碘酶1型（Dio1）和甲状腺激素受体β（TRβ）的表达也显着上调（P < 0.05）。这些变化与整体 DNA 5-mC 甲基化水平显着升高以及甲基转移基因表达增加相关 (P < 0.05)，包括甜菜碱-同型半胱氨酸甲基转移酶 (BHMT)、甘氨酸 N-甲基转移酶 (GNMT) 和 DNA (P < 0.05)。胞嘧啶-5-)-甲基转移酶 1 (DNMT1)。IGF-2基因的启动子区以及IGF-2基因上预测的TRβ结合位点显着低甲基化(P＜0.05)。这些结果表明，通过对肝脏中 IGF 基因家族（尤其是 IGF-2）的表观遗传调节，在鹅饲养者中添加膳食甜菜碱可以改善小鹅的生长。