Hormonal status, metabolic changes, and resting metabolic rate in beef heifers undergoing compensatory growth.
Hormonal status, metabolic changes, and resting metabolic rate in beef heifers undergoing compensatory growth.
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DOI：
10.2527/1996.74157x
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发表时间：
1996
影响因子：
3.3
通讯作者：
E. Yambayamba;M. Price;G. Foxcroft
中科院分区：
文献类型：
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作者：
E. Yambayamba;M. Price;G. Foxcroft
用12头最近断奶的Hereford杂交小母牛，体重227 kg(12 Kg SD)，日龄230d(8d SD)，研究与补偿生长相关的生理反应。6头小母牛被分配到自由采食组(Adlib)，6头小母牛被限制在95d的维持饮食中，然后实现(休息)。分别在限饲(d0，20，48)和断奶(d104,125,153,195)期间采集小母牛血浆，测定生长激素(GH)、胰岛素样生长因子I(IGF-I)、甲状腺激素(T4和T3)、胰岛素、葡萄糖、非酯化脂肪酸(NEFA)、尿素氮(BUN)和3-甲基组氨酸(3-MH)。分别于服药前5d、服药后15d和36d测定静息代谢率(RMR)。饲料限制与第104天(饲喂后第10天)及以后各处理间的差异显著(P<0.05)。相反，静息状态下的小母牛GH浓度在第104天持续升高，但到第125天(实现后第31天)降至即刻水平。在实施10天后，静息状态下的T_4和T_3浓度仍然低于非休眠状态的小母牛(P<；0.05)，但在实施后的第31天上升到对照水平。在产后第15天，静息状态下的RMR低于非休眠状态的小母牛(P<；0.05)；然而，在产后36天，两个处理组之间的RMR没有发现差异。这些结果表明，补偿生长早期生长速度的提高与GH-IGF-I-胰岛素轴的生理反应有关，同时由于限制繁殖小母牛代谢速度较慢，导致维持需求减少。
Twelve recently weaned Hereford crossbred heifers weighing 227 kg (12 kg SD) and aged 230 d (8 d SD) on d 0 were used to investigate physiological responses associated with compensatory growth. Six heifers were allotted to ad libitum intake (ADLIB) and six were restricted to a maintenance diet for 95 d followed by realimentation (REST). Plasma collected from all heifers during feed restriction (d 0, 20, 48) and realimentation (d 104, 125, 153, 195) was analyzed for growth hormone (GH), insulin-like growth factor I (IGF-I), thyroid hormones (thyroxine [T4] and triiodothyronine [T3]), insulin, glucose, nonesterified fatty acids (NEFA), blood urea nitrogen (BUN), and 3-methyl histidine (3-MH). Resting metabolic rate (RMR) was measured 5 d before and 15 and 36 d after the beginning of realimentation. Feed restriction was associated with higher (P .05) between treatments were observed on d 104 (d 10 of realimentation) and thereafter. Conversely, GH concentration in REST heifers remained elevated through d 104 but dropped to ADLIB levels by d 125 (d 31 of realimentation). The T4 and T3 concentrations remained lower (P < .05) in REST than in ADLIB heifers after 10 d of realimentation but rose to control levels by d 31 of realimentation. The RMR was lower (P < .05) in REST than in ADLIB heifers 15 d into realimentation; however, no difference was found between treatments by d 36 of realimentation. These results indicate that enhanced growth rates in the early phase of compensatory growth are associated with the physiological response of the GH-IGF-I-insulin axis coupled with reduced maintenance requirement due to slower metabolic rate in restricted-refed heifers.