Effect of breed, plane of nutrition and age on growth, scrotal development, metabolite concentrations and on systemic gonadotropin and testosterone concentrations following a GnRH challenge in young dairy bulls
Effect of breed, plane of nutrition and age on growth, scrotal development, metabolite concentrations and on systemic gonadotropin and testosterone concentrations following a GnRH challenge in young dairy bulls
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DOI：
10.1016/j.theriogenology.2017.04.002
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发表时间：
2017-07-01
期刊：
影响因子：
2.8
通讯作者：
Kenny, D. A.
中科院分区：
文献类型：
--
作者：
Byrne, C. J.;Fair, S.;Kenny, D. A.
公牛青春期的开始受下丘脑早期GnRH脉动性释放时间的调节，这已被证明受犊牛期营养水平的影响。本研究的目的是确定营养水平对两个对照奶牛品种青春期前公牛生长速度、阴囊发育、代谢产物浓度以及外源性促性腺激素（GnRH）诱导的促黄体生成素（LH）、促卵泡激素（FSH）和睾酮（Ti '）释放的影响。Holstein-Friesian和Jersey公牛犊从3周龄到49周龄被分配到高或低营养水平。在16、24和32周龄时进行强化采血，从静脉注射外源性GnRH前30 min至静脉注射后135 min，每15 min采血一次。每月还收集血液样本并分析胰岛素样生长因子1（IGF-1）、胰岛素、瘦素、脂联素和代谢物浓度。高营养水平公牛的胰岛素和IGF-1水平较高（P < 0.001），但不受品种的影响（P > 0.05）。瘦素水平不受营养水平和品种的影响（P > 0.05）。高营养水平公牛的脂联素水平有升高的趋势（P = 0.05），但不受品种的影响（P > 0.05）。高营养水平的公牛对GnRH的反应性LH浓度较高（P < 0.05），但品种对LH浓度无影响（P > 0.05）。FSH浓度不受品种和营养水平的影响，但随年龄的增长而下降（P < 0.01），LH浓度不受年龄的影响（P > 0.05）。泽西公牛，特别是那些高营养水平的公牛，在青春期前有较高的IT产量（P < 0.001）。使用28厘米作为青春期年龄的代表，营养水平高的公牛预计比营养水平低的公牛更早进入青春期。总之，数据清楚地表明，高营养水平对几种关键的营养和生殖激素产生积极影响，这些激素对乳育公牛犊下丘脑-垂体-睾丸轴的内分泌功能至关重要。(C)2017爱思唯尔公司All rights reserved.
The onset of puberty in the bull is regulated by the timing of early GnRH pulsatility release from the hypothalamus, which has been demonstrated to be affected by plane of nutrition during calf-hood. The aim of this study was to determine the effect of plane of nutrition on growth rate, scrotal development, metabolite concentrations and exogenous gonadotrophin (GnRH) induced release of luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone (Ti') in pre-pubertal bulls of two contrasting dairy breeds. Holstein-Friesian and Jersey bull calves were assigned to either a high or low plane of nutrition from 3 to 49 weeks of age. Intensive blood sampling was conducted at 16, 24 and 32 weeks of age, every 15 min from 30 min prior to intravenous administration of exogenous GnRH to 135 min after. Monthly blood samples were also collected and analyzed for insulin like growth factor 1 (IGF-1), insulin, leptin, adiponectin and metabolite concentration. Insulin and IGF-1 were higher in bulls on a high plane of nutrition (P < 0.001) but were not affected by breed (P > 0.05). Leptin was not affected by plane of nutrition or breed (P > 0.05). Adiponectin tended to be higher in bulls on a high plane of nutrition (P = 0.05), but was not affected by breed (P > 0.05). Bulls on a high plane of nutrition had a greater concentration of LH in response to GnRH (P < 0.05) but there was no effect of breed (P > 0.05). FSH concentration was not influenced by breed or plane of nutrition but FSH concentrations did decrease with age (P < 0.01), while, LH was not affected by age (P > 0.05). Jersey bulls, particularly those on a high plane of nutrition, had higher IT production in the pre-pubertal period (P < 0.001). Using 28 cm as a proxy for age at puberty, bulls on a high plane of nutrition were predicted to reach puberty earlier than bulls on a low plane. In conclusion, the data clearly demonstrate that a high plane of nutrition positively affects several key nutritional and reproductive hormones which are critical to the endocrinological functionality of the hypothalamic-pituitary-testicular axis in dairy-bred bull calves. (C) 2017 Elsevier Inc. All rights reserved.