Connor E E, Barao S M, Douglass L W, Zinn S A, Dahl G E
Department of Animal and Avian Sciences, University of Maryland, College Park 20742-2311, USA.
J Anim Sci. 1999 Oct;77(10):2736-41. doi: 10.2527/1999.77102736x.
Development of practical, physiologically based methods that provide an early, yet accurate, evaluation of a bull's genetic merit could benefit the beef industry. The use of GH response to a single, acute dose of GHRH was evaluated as a predictor of future growth performance and carcass characteristics of weanling bulls. Fifty-six Angus bulls averaging 229 d (SD = 27) of age were administered three doses i.v. (0, 1.5, and 4.5 microg/100 kg BW) of human GHRH (1-29) analog in a Latin square design balanced for residual effects. Blood samples were collected via jugular catheter at -60, -45, -30, -15, 0, 5, 10, 15, 30, 45, 60, 90 and 120 min relative to GHRH injection. Serum concentrations of GH were plotted over time. Response to GHRH was calculated as the area under the GH response curve (AUC-GH) using the trapezoidal approximation. Relationships between AUC-GH, weaning weight adjusted to 205 d of age (205-d WW), and direct weaning weight EPD (WWEPD) versus age-adjusted BW (BWadj), ADG, and carcass measurements from a 140-d growth performance test were evaluated using simple linear regression. A positive correlation between AUC-GH and ADG and an inverse relationship between AUC-GH and carcass fat were observed. The present study provides evidence that AUC-GH is a better predictor of future growth performance in beef bulls than 205-d WW or WWEPD values. Thus, GH response to GHRH is associated with subsequent growth and may be a useful tool for sire selection in beef production.
开发实用的、基于生理学的方法，以便对公牛的遗传价值进行早期且准确的评估，这可能会使牛肉行业受益。对单次急性剂量的生长激素释放激素（GHRH）的生长激素（GH）反应被评估为断奶公牛未来生长性能和胴体特征的预测指标。56头平均年龄为229天（标准差 = 27）的安格斯公牛，按照拉丁方设计静脉注射三剂（0、1.5和4.5微克/100千克体重）人GHRH（1 - 29）类似物，以平衡残留效应。在相对于GHRH注射的 - 60、 - 45、 - 30、 - 15、0、5、10、15、30、45、60、90和120分钟时，通过颈静脉导管采集血样。绘制血清生长激素浓度随时间的变化图。使用梯形近似法将对GHRH的反应计算为生长激素反应曲线下面积（AUC - GH）。使用简单线性回归评估AUC - GH、调整到205日龄的断奶体重（205 - d WW）、直接断奶体重预期子代差异（WWEPD）与年龄调整体重（BWadj）、平均日增重（ADG）以及140天生长性能测试的胴体测量值之间的关系。观察到AUC - GH与ADG之间呈正相关，AUC - GH与胴体脂肪之间呈负相关。本研究提供的证据表明，对于肉牛公牛未来的生长性能，AUC - GH比205 - d WW或WWEPD值是更好的预测指标。因此，对GHRH的生长激素反应与后续生长相关，可能是牛肉生产中种公牛选择的有用工具。
