Animal and Bioscience Department, Teagasc, Dunsany, Co. Meath, C15 PW93, Ireland; School of Agriculture and Food Science, University College Dublin, Belfield, Dublin, D04 F6X4, Ireland.
Laboratory of Animal Reproduction, Department of Biological Sciences, University of Limerick, Limerick, V94 T9PX, Ireland.
J Dairy Sci. 2018 Apr;101(4):3460-3475. doi: 10.3168/jds.2017-13720. Epub 2018 Feb 4.
The aim of this study was (1) to examine the effect of plane of nutrition during the first and second 6 mo of life on systemic concentrations of reproductive hormones and metabolites in Holstein-Friesian dairy bulls, and (2) to establish relationships with age at puberty and postpubertal semen production potential. Holstein-Friesian bull calves (n = 83) with a mean (standard deviation) age and body weight of 17 (4.4) d and 52 (6.2) kg, respectively, were assigned to a high or low plane of nutrition for the first 6 mo of life. At 24 wk of age, bulls were reassigned, within treatment, either to remain on the same diet or to switch to the opposite diet until puberty, resulting in 4 treatment groups: high-high, high-low, low-low, and low-high. Monthly blood samples were analyzed for metabolites (albumin, urea, total protein, β-hydroxybutyrate, glucose, nonesterified fatty acid, triglycerides and creatinine), insulin, insulin-like growth factor-1, leptin, adiponectin, FSH, and testosterone. A GnRH challenge was carried out at 16 and 32 wk of age (n = 9 bulls per treatment). Blood was collected at 15-min intervals for 165 min, with GnRH administered (0.05 mg/kg of body weight, i.v.) immediately after the third blood sample. Blood samples were subsequently analyzed for LH, FSH, and testosterone. Stepwise regression was used to detect growth and blood measurements to identify putative predictors of age at puberty and subsequent semen quality traits. Metabolic hormones and metabolites, in general, reflected metabolic status of bulls. Although FSH was unaffected by diet, it decreased with age both in monthly samples and following GnRH administration. Testosterone was greater in bulls on the high diet before and after 6 mo of age. Testosterone concentrations increased dramatically after 6 mo of age. Luteinizing hormone was unaffected by diet following GnRH administration but basal serum LH was greater in bulls on a high diet before 6 mo of age. In conclusion, the plane of nutrition offered before 6 mo of age influenced metabolic profiles, which are important for promoting GnRH pulsatility, in young bulls.
（1）研究生命最初 6 个月和第二个 6 个月的营养水平对荷斯坦弗里森奶牛公牛生殖激素和代谢物系统浓度的影响；（2）确定其与初情期年龄和青春期后精液生产潜力的关系。将 83 头荷斯坦弗里森公牛犊（平均[标准差]年龄和体重分别为 17[4.4]天和 52[6.2]kg）分别分配到生命最初 6 个月的高或低营养水平。在 24 周龄时，根据处理情况，将公牛重新分配，要么继续保持相同的饮食，要么切换到相反的饮食，直到青春期，从而形成 4 个处理组：高高、高低、低低和低高。每月分析血液样本的代谢物（白蛋白、尿素、总蛋白、β-羟丁酸、葡萄糖、非酯化脂肪酸、甘油三酯和肌酐）、胰岛素、胰岛素样生长因子-1、瘦素、脂联素、FSH 和睾酮。在 16 和 32 周龄时对所有公牛（每个处理 9 头）进行 GnRH 挑战。在 165 分钟内以 15 分钟的间隔采集血液，在第三次采血后立即静脉内给予 GnRH（0.05mg/kg 体重）。随后分析 LH、FSH 和睾酮。逐步回归用于检测生长和血液测量，以确定初情期和随后精液质量特征的潜在预测因子。代谢激素和代谢物通常反映了公牛的代谢状况。尽管饮食对 FSH 没有影响，但它在每月样本和 GnRH 给药后均随年龄而降低。在 6 个月之前和之后，高营养饮食的公牛的睾酮更高。睾酮浓度在 6 个月后急剧增加。在 GnRH 给药后，饮食对 LH 没有影响，但在 6 个月之前，高营养饮食的公牛基础血清 LH 更高。总之，在 6 个月之前提供的营养水平影响了代谢谱，这对于促进 GnRH 脉冲性很重要。
