Enright W J, Chapin L T, Moseley W M, Zinn S A, Tucker H A
J Dairy Sci. 1986 Feb;69(2):344-51. doi: 10.3168/jds.s0022-0302(86)80412-x.
Serum growth hormone was determined in lactating cows following repeated intravenous injections of growth hormone-releasing factor. A given dose was injected every 4 h for 24 h in a 4 (cow) X 4 (d) Latin square. Growth hormone increased similarly above controls after 10, 20, or 40 micrograms releasing factor/100 kg body weight. In another experiment the effects on lactational performance and growth hormone responses of cows to repeated injections of releasing factor for 10 d were determined in a 2 (cow) X 2 (period) Latin square crossover. Administration of 20 micrograms releasing factor/100 kg body weight to 16 Holstein cows (lactating 4.5 to 7.5 mo) every 4-h for 10 d increased milk yield from 25.4 to 27.7 kg/d and increased total fat, protein, and lactose 11% above controls. Releasing factor did not affect milk composition or feed intake. Peak growth hormone response to releasing factor was similar between d 1 (19.9 ng/ml) and 10 (24.4 ng/ml). Exogenous growth hormone-releasing factor administered to lactating Holstein cows at the doses tested: 1) increases growth hormone consistently, although the response is not dose dependent, 2) is galactopoietic, 3) causes an apparent increase in feed to milk conversion, and 4) increases growth hormone to at least the same magnitude on d 10 as on d 1.
在对泌乳奶牛反复静脉注射生长激素释放因子后，测定了其血清生长激素水平。采用4（奶牛）×4（天）拉丁方设计，每4小时注射一次给定剂量，共注射24小时。在注射10、20或40微克释放因子/100千克体重后，生长激素水平相对于对照组有相似程度的升高。在另一项实验中，采用2（奶牛）×2（时间段）拉丁方交叉设计，测定了奶牛连续10天反复注射释放因子对泌乳性能和生长激素反应的影响。对16头荷斯坦奶牛（泌乳4.5至7.5个月）每4小时注射一次20微克释放因子/100千克体重，持续10天，使产奶量从25.4千克/天增加到27.7千克/天，总脂肪、蛋白质和乳糖含量比对照组提高了11%。释放因子对牛奶成分或采食量没有影响。第1天（19.9纳克/毫升）和第10天（24.4纳克/毫升）对释放因子的生长激素峰值反应相似。以测试剂量给泌乳荷斯坦奶牛注射外源性生长激素释放因子：1）能持续增加生长激素，尽管反应不依赖剂量；2）具有催乳作用；3）使饲料转化率明显提高；4）在第10天生长激素增加幅度至少与第1天相同。
