Lapierre H, Pelletier G, Petitclerc D, Dubreuil P, Morisset J, Gaudreau P, Couture Y, Brazeau P
Agriculture Canada Research Station, Lennoxville, Quebec.
J Dairy Sci. 1988 Jan;71(1):92-8. doi: 10.3168/jds.S0022-0302(88)79529-6.
Twelve cows (209 d in lactation, 642 kg BW) were used in an experiment conducted over four 10-d periods (one preinjection, one injection, and two postinjection). Gelatine (n = 6) or 10 mg of growth hormone-releasing factor in gelatine (n = 6) was injected subcutaneously at 1000 h every day on d 11 to 20. Data were averaged for the last 5 d of each period. During the injection period, milk, fat, and protein yields increased by 3 kg.d-1 (14.3%), .14 kg.d-1 (16.7%), and .12 kg.d-1 (15.4%), respectively. Moreover, milk, fat, and protein yields for the treated cows remained higher than for the control cows until the last postinjection period. Growth hormone response was evaluated from blood samples withdrawn from 2 h prior to 8 h postinjection on d 11, 15, and 20 and on d 40. After growth hormone-releasing factor injection, peaks and area under the curve were 24.5, 30.8, and 47.0 ng.ml-1 and 2475, 3979, and 3741 ng.ml-1.min-1 on d 11, 15, and 20, respectively. On d 40, there was no difference in growth hormone concentrations in blood between control and treated cows. These results demonstrate that 10 d of daily injection of a growth hormone-releasing factor increases milk production by 14.3% (3 kg.d-1) and still induces growth hormone release at the end of the injection period without any sign of refractoriness.
选用12头奶牛（泌乳期209天，体重642千克）进行一项实验，实验为期4个10天阶段（一个注射前阶段、一个注射阶段和两个注射后阶段）。在第11至20天，每天1000时皮下注射明胶（n = 6）或含10毫克生长激素释放因子的明胶（n = 6）。各阶段最后5天的数据取平均值。在注射阶段，牛奶、脂肪和蛋白质产量分别增加了3千克·天⁻¹（14.3%）、0.14千克·天⁻¹（16.7%）和0.12千克·天⁻¹（15.4%）。此外，在最后一个注射后阶段之前，处理组奶牛的牛奶、脂肪和蛋白质产量一直高于对照组奶牛。在第11、15、20天和第40天，于注射前2小时至注射后8小时采集血样，评估生长激素反应。注射生长激素释放因子后，第11、15和20天的生长激素峰值分别为24.5、30.8和47.0纳克·毫升⁻¹，曲线下面积分别为2475、3979和3741纳克·毫升⁻¹·分钟⁻¹。在第40天，对照组和处理组奶牛血液中的生长激素浓度无差异。这些结果表明，连续10天每日注射生长激素释放因子可使牛奶产量提高14.3%（3千克·天⁻¹），并且在注射期结束时仍能诱导生长激素释放，且无任何不应性迹象。
