The objective of this study was to examine the effect of nutrition during the first 12 wk of life on aspects of the physiological and transcriptional regulation of testicular and overall sexual development in the bull calf. Holstein Friesian bull calves with a mean (SD) age and bodyweight of 17.5 (2.85) d and 48.8 (5.30) kg, respectively, were assigned to either a high (HI; n = 15) or moderate (MOD; n = 15) plane of nutrition and were individually fed milk replacer and concentrate to achieve overall target growth rates of at least 1.0 and 0.5 kg/d, respectively. Throughout the trial, animal growth performance, feed intake, and systemic concentrations of metabolites, metabolic hormones, and reproductive hormones were assessed. Additionally, pulsatility of reproductive hormones (luteinizing hormone, follicle-stimulating hormone, and testosterone) was recorded at 15-min intervals during a 10-h period at 10 wk of age. At 87 ± 2.14 d of age, all calves were euthanized, testes were weighed, and testicular tissue was harvested. Differential expression of messenger ribonucleic acid (mRNA) candidate genes involved in testicular development was examined using quantitative polymerase chain reaction assays. All data were analyzed using the MIXED procedure in Statistical Analysis Software using terms for treatment as well as time for repeated measures. Blood metabolites and metabolic hormones generally reflected the improved metabolic status of the calves on the HI plane of nutrition though the concentrations of reproductive hormones were not affected by diet. Calves on the HI diet had greater mean (SED) slaughter weight (112.4 vs. 87.70 [2.98] kg; P < 0.0001) and testicular tissue weight (29.2 vs. 20.1 [2.21] g; P = 0.0003) than those on the MOD diet. Relative mRNA abundance data indicated advanced testicular development through upregulation of genes involved in cellular metabolism (SIRT1; P = 0.0282), cholesterol biosynthesis (EBP; P = 0.007), testicular function (INSL3; P = 0.0077), and Sertoli cell development (CLDN11; P = 0.0054) in HI compared with MOD calves. In conclusion, results demonstrate that offering dairy-bred male calves a high plane of nutrition during the first 3 mo of life not only improves growth performance and metabolic status but also advances testicular development consistent with more precocious sexual maturation.

中文翻译：

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出生后前 12 周营养水平对断奶前荷斯坦弗里西亚公牛犊的生长、代谢和生殖激素浓度以及睾丸相对 mRNA 丰度的影响

本研究的目的是检查在生命的前 12 周内营养对公牛小牛睾丸和整体性发育的生理和转录调控方面的影响。平均 (SD) 年龄和体重分别为 17.5 (2.85) d 和 48.8 (5.30) kg 的荷斯坦弗里西亚公牛犊被分配到高 (HI; n = 15) 或中等 (MOD; n = 15)营养平面，分别饲喂代乳粉和浓缩物，以分别达到至少 1.0 和 0.5 kg/d 的总体目标生长速度。在整个试验过程中，评估了动物生长性能、采食量以及代谢物、代谢激素和生殖激素的全身浓度。此外，生殖激素（促黄体激素、促卵泡激素、和睾酮）在 10 周龄时的 10 小时内每隔 15 分钟记录一次。在 87 ± 2.14 日龄时，对所有小牛实施安乐死，称重睾丸，并收获睾丸组织。使用定量聚合酶链反应测定法检查了参与睾丸发育的信使核糖核酸 (mRNA) 候选基因的差异表达。使用统计分析软件中的 MIXED 程序分析所有数据，使用治疗术语和重复测量时间。尽管生殖激素的浓度不受饮食的影响，但血液代谢物和代谢激素通常反映了小牛在 HI 营养平面上的代谢状态改善。HI 饮食的小牛平均 (SED) 屠宰重量更大（112.4 对 87.70 [2.98] kg；P < 0。0001) 和睾丸组织重量 (29.2 vs. 20.1 [2.21] g; P = 0.0003) 比 MOD 饮食。相对 mRNA 丰度数据表明，通过上调参与细胞代谢 (SIRT1; P = 0.0282)、胆固醇生物合成 (EBP; P = 0.007)、睾丸功能 (INSL3; P = 0.0077) 和支持细胞发育 (CLDN11) 的基因，促进睾丸发育; P = 0.0054) HI 与 MOD 小牛相比。总之，结果表明，在生命的前 3 个月内为奶牛饲养的雄性小牛提供高水平的营养不仅可以改善生长性能和代谢状态，而且可以促进睾丸发育，与更早熟的性成熟相一致。相对 mRNA 丰度数据表明，通过上调参与细胞代谢 (SIRT1; P = 0.0282)、胆固醇生物合成 (EBP; P = 0.007)、睾丸功能 (INSL3; P = 0.0077) 和支持细胞发育 (CLDN11) 的基因，促进睾丸发育; P = 0.0054) HI 与 MOD 小牛相比。总之，结果表明，在生命的前 3 个月内为奶牛饲养的雄性小牛提供高水平的营养不仅可以改善生长性能和代谢状态，而且可以促进睾丸发育，与更早熟的性成熟相一致。相对 mRNA 丰度数据表明，通过上调参与细胞代谢 (SIRT1; P = 0.0282)、胆固醇生物合成 (EBP; P = 0.007)、睾丸功能 (INSL3; P = 0.0077) 和支持细胞发育 (CLDN11) 的基因，促进睾丸发育; P = 0.0054) HI 与 MOD 小牛相比。总之，结果表明，在生命的前 3 个月内为奶牛饲养的雄性小牛提供高水平的营养不仅可以改善生长性能和代谢状态，而且可以促进睾丸发育，与更早熟的性成熟相一致。