Enright W J, Chapin L T, Moseley W M, Tucker H A
Department of Animal Science, Animal Reproduction Laboratory, Michigan State University, East Lansing 48824.
J Dairy Sci. 1988 Jan;71(1):99-108. doi: 10.3168/jds.S0022-0302(88)79530-2.
In a first experiment growth hormone was determined in serum of lactating cows infused intravenously with bovine growth hormone-releasing factor for 24 h. Concentrations of growth hormone increased 5 times above placebo after 3.125, 6.25, 12.5, 25.0, or 50.0 mg releasing factor/cow per 24 h. Releasing factor increased the pulsatile nature of growth hormone release. In a second experiment we determined effects of intravenous infusions of releasing factor for 20 d on growth hormone and lactation in primiparous cows (n = 5/treatment; 144 +/- 7 d after parturition). Milk yield of placebo-infused cows averaged 26.5 +/- 1.7 kg/d during d 6 to 20 of infusion. Infusions of 1 and 3 mg releasing factor/cow per 24 h increased milk yield 11 and 23%, respectively. Releasing factor had only small effects on milk composition, net energy intake, and BW. Releasing factor did not affect energy efficiency of milk production (energy output in milk per unit of net energy intake) when corrected for BW changes. Average growth hormone across d 1, 10, and 19 of infusion was 2.1, 4.1, and 6.8 ng/ml serum for placebo, 1, and 3 mg releasing factor, respectively. Infusions of bovine growth hormone-releasing factor: 1) increased mean and pulsatile release of growth hormone during 24 h and 20 d, 2) increased milk yield in a dose-dependent manner, and 3) did not affect BW-corrected energy efficiency of milk production.
在首个实验中，测定了静脉内注射牛生长激素释放因子24小时的泌乳奶牛血清中的生长激素。每头奶牛每24小时注射3.125、6.25、12.5、25.0或50.0毫克释放因子后，生长激素浓度比注射安慰剂后增加了5倍。释放因子增加了生长激素释放的脉冲特性。在第二个实验中，我们测定了对初产奶牛（每组n = 5；分娩后144±7天）静脉输注释放因子20天对生长激素和泌乳的影响。在输注的第6至20天，注射安慰剂的奶牛平均产奶量为26.5±1.7千克/天。每头奶牛每24小时输注1毫克和3毫克释放因子分别使产奶量提高了11%和23%。释放因子对牛奶成分、净能量摄入量和体重影响较小。校正体重变化后，释放因子不影响牛奶生产的能量效率（每单位净能量摄入的牛奶能量输出）。在输注的第1、10和19天，注射安慰剂、1毫克和3毫克释放因子的奶牛血清中生长激素的平均浓度分别为2.1、4.1和6.8纳克/毫升。静脉输注牛生长激素释放因子：1）在24小时和20天内增加了生长激素的平均释放量和脉冲释放量；2）以剂量依赖的方式提高了产奶量；3）不影响校正体重后的牛奶生产能量效率。
