Stumpf T T, Wolfe M W, Roberson M S, Kittok R J, Kinder J E
Department of Animal Science, University of Nebraska-Lincoln 68583-0908.
Biol Reprod. 1993 Nov;49(5):1089-95. doi: 10.1095/biolreprod49.5.1089.
Serum concentrations of LH vary with season of the year in ovariectomized beef and dairy cows. The objective of the present study was to determine whether concentrations and profile of the gonadotropins and testosterone (T) in circulation vary with season of year in bovine males of a composite breed type (beef). Five INTACT and five gonadectomized (GNX) males that were 22 mo of age at the initiation of the study were used. All of the males utilized were maintained on pasture throughout the year at the latitude of 41 degrees N. Blood samples were collected in a serial regimen (10-min intervals for 24 h) at the spring and fall equinox and the summer and winter solstice. Concentrations of LH were quantified in all samples, and concentrations of T were determined in all samples of the INTACT group. Concentrations of FSH and 17 beta-estradiol (E2) were quantified in pooled samples for all animals, while concentrations of T were determined in pooled samples for males from the GNX group. Pulse frequency of LH or T and mean concentration of FSH did not vary with season of the year. A seasonal effect on mean concentration of LH (p < 0.01) occurred in males of the GNX group, with mean concentrations of LH being greatest during the spring equinox and lowest during the winter solstice. Season had an effect on pulse amplitude of LH (p < 0.01), mean concentration of T (p < 0.01), and pulse amplitude of T (p < 0.05) in males from the INTACT group.(ABSTRACT TRUNCATED AT 250 WORDS)
在切除卵巢的肉牛和奶牛中，促黄体生成素（LH）的血清浓度随季节变化。本研究的目的是确定在复合品种类型（肉牛）的公牛中，循环中促性腺激素和睾酮（T）的浓度及变化曲线是否随季节变化。使用了5头完整和5头去势（GNX）的公牛，研究开始时它们的年龄为22个月。所有使用的公牛全年都饲养在北纬41度的牧场。在春分、秋分、夏至和冬至时，按照连续方案（每隔10分钟采集一次，共采集24小时）采集血样。对所有样本中的LH浓度进行定量，对完整组的所有样本测定T浓度。对所有动物的混合样本中的促卵泡生成素（FSH）和17β - 雌二醇（E2）浓度进行定量，而对去势组雄性的混合样本测定T浓度。LH或T的脉冲频率以及FSH的平均浓度不随季节变化。去势组雄性的LH平均浓度存在季节性影响（p < 0.01），LH平均浓度在春分最高，冬至最低。季节对完整组雄性的LH脉冲幅度（p < 0.01）、T平均浓度（p < 0.01）和T脉冲幅度（p < 0.05）有影响。（摘要截短至250字）
