Sartin J L, Kemppainen R J, Cummins K A, Williams J C
Department of Physiology and Pharmacology, College of Veterinary Medicine, Auburn University 36849.
J Dairy Sci. 1988 Mar;71(3):650-7. doi: 10.3168/jds.S0022-0302(88)79603-4.
Concentrations of insulin, glucagon, growth hormone, adrenocorticotropin, and cortisol were determined in plasma samples obtained at 20-min intervals for 6 h from low and high producing dairy cows at d 30 and 90 postpartum. Four nonpregnant, nonlactating cows also were sampled. Insulin concentrations were reduced at d 30 in both groups of lactating cows compared with concentrations in nonlactating cows; glucagon concentrations were unchanged. The molar insulin: glucagon was reduced at d 30 in both groups and at d 90 for low, but not high producers. Growth hormone concentrations were higher at d 30 in high producers than at d 90, in low producers at d 30, and higher than in nonlactating cows. Cortisol concentrations were lower in high producing cows at d 30 than at d 90 or in nonlactating cows due to a reduced pulse amplitude. No differences were observed for adrenocorticotropin. Reduced molar insulin: glucagon may be an integral response of the cow to lactation, while the difference in the insulin: glucagon for high and low producers at d 90 postpartum may indicate a continued need for a gluconeogenic stimulus in low producers. The elevated growth hormone and low cortisol concentrations likely participate in the enhanced production observed in high producing dairy cows.
在产后第30天和第90天，每隔20分钟从高产和低产奶牛采集血浆样本，持续6小时，测定其中胰岛素、胰高血糖素、生长激素、促肾上腺皮质激素和皮质醇的浓度。同时也对4头未怀孕、未泌乳的奶牛进行了采样。与未泌乳奶牛相比，两组泌乳奶牛在产后第30天的胰岛素浓度均降低；胰高血糖素浓度未发生变化。两组奶牛在产后第30天以及低产奶牛在产后第90天的胰岛素与胰高血糖素摩尔比均降低，但高产奶牛在产后第90天未降低。高产奶牛在产后第30天的生长激素浓度高于产后第90天，低产奶牛在产后第30天的生长激素浓度高于未泌乳奶牛，且高于其产后第90天的浓度。由于脉冲幅度降低，高产奶牛在产后第30天的皮质醇浓度低于产后第90天或未泌乳奶牛。促肾上腺皮质激素未观察到差异。胰岛素与胰高血糖素摩尔比降低可能是奶牛对泌乳的一种整体反应，而产后第90天高产和低产奶牛胰岛素与胰高血糖素的差异可能表明低产奶牛持续需要糖异生刺激。生长激素升高和皮质醇浓度降低可能参与了高产奶牛的产奶量增加。
