Kesler D J, Garverick H A
J Dairy Sci. 1977 Apr;60(4):632-4. doi: 10.3168/jds.S0022-0302(77)83912-X.
Twelve bull calves, 2 to 24 days of age, were assigned to two groups of six calves and administered a single 50 microng intramuscular injection of gonadotropin releasing hormone. Bull calves in group 1 were 2 to 5 days of age (mean 3.0 days), and bull calves in group 2 were 10 to 24 days of age (mean 17.1 days). Blood plasma for radioimmunoassay of luteinizing hormone and testosterone was collected at .5-h intervals for 3-h and at 4- and 6-h following treatment. With increasing age, preinjection luteinizing hormone concentrations in plasma decreased while preinjection testosterone concentrations increased. Mean preinjection luteinizing hormone concentrations for group 1 (1.01 +/- .07 ng/ml; mean +/- standard error) were higher than for group 2 (.61 +/- .12 ng/ml). Preinjection luteinizing hormone and testosterone concentrations were correlated--.63. Following treatment, luteinizing hormone increased with mean peak concentrations of 7.28 +/- .74 and 6.95 +/- 1.79 ng/ml for groups 1 and 2. Peak testosterone response following gonadotropin releasing hormone was higher for group 2 than 1 (1077 +/- 253 versus 436 +/- 116 pg/ml).
12头2至24日龄的公犊牛被分为两组，每组6头，每头犊牛均接受一次50微克促性腺激素释放激素的肌肉注射。第1组公犊牛年龄为2至5日龄（平均3.0日龄），第2组公犊牛年龄为10至24日龄（平均17.1日龄）。在注射前以及注射后0.5小时内每隔0.5小时、3小时、4小时和6小时采集血浆，用于促黄体生成素和睾酮的放射免疫分析。随着年龄增长，注射前血浆中促黄体生成素浓度降低，而注射前睾酮浓度升高。第1组注射前促黄体生成素平均浓度（1.01±0.07纳克/毫升；平均值±标准误）高于第2组（0.61±0.12纳克/毫升）。注射前促黄体生成素和睾酮浓度呈负相关，相关系数为-0.63。注射后，促黄体生成素升高，第1组和第2组的平均峰值浓度分别为7.28±0.74和6.95±1.79纳克/毫升。第2组促性腺激素释放激素注射后睾酮的峰值反应高于第1组（1077±253对436±116皮克/毫升）。
