This study investigated the effects of the dietary threonine (Thr) levels on the performance, offspring traits, embryo amino acid transportation, and protein deposition in breeder hens of yellow-feathered chickens. In total, 720 breeder hens of Lingnan yellow-feathered chickens were randomly assigned to 1 of 6 dietary treatments, with 6 replicates per treatment (20 birds per replicate). The breeder hens were fed either basal diet (Thr = 0.38%) or basal diet supplemented with 0.12, 0.24, 0.36, 0.48, or 0.60% Thr from 197 to 266 D. There was a positive response in terms of the laying rate after adding different levels of Thr to the diet, but no significant effects on the average daily gain, average daily egg weight, feed conversion ratio, average broken eggs, and unqualified egg rate (P > 0.05). However, the eggshell strength and eggshell percentage decreased in a linear manner as the dietary Thr concentration increased (P = 0.05). Dietary supplementation with Thr had significant effects on the expression of mucin 2 (MUC2) in the uterus and zonula occludens protein 1 (ZO-1) in the duodenum of breeders (P < 0.05). In chick embryos at embryonic age 18 D, significant upregulation of poultry target of rapamycin (pTOR) occurred in the liver and breast muscle, as well as threonine dehydrogenase (TDH) in the thigh, and aminopeptidase (ANPEP) (P < 0.05) in the duodenum and ileum due to dietary Thr supplementation, but there were no effects on MUC2 expression in the duodenum and ileum (P > 0.05). The livability of the progeny broilers tended to increase with the dietary Thr concentration (quadratic, P = 0.08). Thus, dietary supplementation with Thr had positive effects on the laying production by breeder hens and offspring performance, and it also regulated the expression levels of genes related to amino acid transportation and protein deposition. The optimal dietary Thr concentration that maximized the laying rate in yellow-feathered chicken breeders aged 197 to 266 D was 0.68% according to quadratic regression analysis.

中文翻译：

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日粮苏氨酸补充对黄羽鸡种母鸡及其后代生产力和蛋白质沉积和氨基酸转运相关基因表达的影响。

本研究调查了日粮苏氨酸 (Thr) 水平对黄羽鸡种母鸡生产性能、后代性状、胚胎氨基酸转运和蛋白质沉积的影响。总共有 720 只岭南黄羽鸡种鸡被随机分配到 6 种日粮处理中的一种，每个处理 6 个重复（每个重复 20 只鸡）。从 197 天到 266 天，种鸡饲喂基础日粮（Thr = 0.38%）或添加 0.12、0.24、0.36、0.48 或 0.60% Thr 的基础日粮。添加后产蛋率有积极反应不同水平的Thr对日粮的平均日增重、平均日蛋重、饲料转化率、平均破蛋率、不合格蛋率无显着影响（P > 0.05）。然而，随着日粮苏氨酸浓度的增加，蛋壳强度和蛋壳百分比呈线性下降（P = 0.05）。日粮添加Thr对种鸡子宫粘蛋白2（MUC2）和十二指肠闭合带蛋白1（ZO-1）的表达有显着影响（P < 0.05）。在 18 D 龄的鸡胚胎中，家禽雷帕霉素靶蛋白 (pTOR) 显着上调发生在肝脏和胸肌，大腿苏氨酸脱氢酶 (TDH) 和氨肽酶 (ANPEP) (P < 0.05)十二指肠和回肠由于膳食补充苏氨酸，但对十二指肠和回肠中的 MUC2 表达没有影响（P > 0.05）。后代肉鸡的成活率随着日粮 Thr 浓度的增加而增加（二次方，P = 0.08）。因此，日粮中添加 Thr 对种鸡的产蛋性能和后代性能有积极影响，还能调节氨基酸转运和蛋白质沉积相关基因的表达水平。根据二次回归分析，使 197 至 266 日龄黄羽鸡种鸡的产蛋率最大化的最佳日粮 Thr 浓度为 0.68%。