Dawson J M, Craigon J, Buttery P J, Beever D E
Department of Applied Biochemistry and Food Science, Faculty of Agricultural and Food Sciences, University of Nottingham Sutton Bonington Campus, Loughborough, Leicestershire.
Br J Nutr. 1993 Jul;70(1):93-102. doi: 10.1079/bjn19930107.
The effect of feeding grass silage or a forage-concentrate (dried grass-barley) diet ad lib. to young cattle on growth rate, plasma growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentrations was examined. The effect of including the beta-adrenergic agonist cimaterol in the forage-concentrate diet was also investigated. Significantly higher growth rates were observed in animals fed on the forage-concentrate diet than in those fed on the silage diet (P < 0.001), and these were further enhanced by dietary inclusion of cimaterol (P < 0.05). Plasma GH levels were higher in the silage-fed animals (P < 0.001) but IGF-1 levels were significantly lower (P < 0.001) than in the forage-concentrate-fed animals. Cimaterol had no effect on mean plasma GH and IGF-1 concentrations. Nevertheless, plasma IGF-1 levels correlated positively with growth rate across all three treatments (r 0.84, P < 0.001, n 17). Spectral analysis of the GH data obtained for each animal was used to determine whether regular periodicities could be detected in the 24 h profile and whether they differed between the three treatment groups. Regular periodicities of four-five cycles/d were detected in the averaged GH profiles of the silage-fed and the control forage-concentrate-fed animals. In contrast, in animals given cimaterol regular GH cycles were not detectable at any of the frequencies tested. This suggests that cimaterol disrupts the rhythm of GH secretion without altering the overall mean concentrations. The data also suggest that due to an inadequate nutrient supply, the GH-IGF-1 regulatory mechanism was uncoupled in the cattle fed on silage, which may have contributed to the poor growth response of these animals.
研究了让幼牛随意采食青贮草或草料 - 精料（干草 - 大麦）日粮对其生长速率、血浆生长激素（GH）和胰岛素样生长因子 -1（IGF -1）浓度的影响。同时还研究了在草料 - 精料日粮中添加β - 肾上腺素能激动剂西马特罗的效果。结果发现，采食草料 - 精料日粮的动物生长速率显著高于采食青贮日粮的动物（P < 0.001），并且日粮中添加西马特罗可进一步提高生长速率（P < 0.05）。青贮日粮喂养的动物血浆GH水平较高（P < 0.001），但IGF -1水平显著低于草料 - 精料日粮喂养的动物（P < 0.001）。西马特罗对血浆GH和IGF -1的平均浓度没有影响。然而，在所有三种处理中，血浆IGF -1水平与生长速率呈正相关（r = 0.84，P < 0.001，n = 17）。对每只动物获得的GH数据进行频谱分析，以确定在24小时曲线中是否能检测到规律的周期性，以及三个处理组之间是否存在差异。在青贮日粮喂养和对照草料 - 精料日粮喂养动物的平均GH曲线中检测到了每天4 - 5个周期的规律周期性。相比之下，在给予西马特罗的动物中，在任何测试频率下都未检测到规律的GH周期。这表明西马特罗在不改变总体平均浓度的情况下破坏了GH分泌的节律。数据还表明，由于营养供应不足，青贮日粮喂养的牛中GH - IGF -1调节机制未耦合，这可能是这些动物生长反应不佳的原因。
