Hayden J M, Williams J E, Collier R J
Department of Animal Sciences, University of Missouri, Columbia 65211.
J Anim Sci. 1993 Dec;71(12):3327-38. doi: 10.2527/1993.71123327x.
Eighteen Chianina crossbred steers were used to examine the interrelationship between hormonal status and empty body protein (EBPRT) and fat (EBFAT) accretion during an 88-d controlled realimentation (REAL; DMI was adjusted weekly on an individual BW basis) period. Body composition was determined by monitoring endogenous whole-body 40[K]. At the end of restriction (REST) and on d 31 and 59 of REAL blood samples were taken and analyzed for concentrations of growth hormone (GH), IGF-I, IGF-II, insulin (INS), thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3), nonesterified fatty acids (NEFA), glucose, and urea nitrogen. Depositions of EBPRT and EBFAT were decreased (P < .001) in REST (92 d) animals compared with nonrestricted (NR) controls. During REST, plasma levels of glucose, IGF-I, INS, T4, T3, and rT3 were decreased (P < .05); plasma urea nitrogen (PUN), NEFA, and GH levels were increased (P < .05), and IGF-II concentrations were similar between REST and NR steers. A transient compensatory response in BW gain and protein deposition occurred in repleted steers between d 35 and 62 of REAL. During this period, PUN levels markedly declined (P < .01) in REAL steers and glucose concentration increased (P < .01) to levels similar to those in NR controls. This response prevailed even though apparent digestible nutrients were decreased in repleted animals. During energy repletion, plasma levels of T4, T3, rT3, IGF-I, and INS were positively, and of GH was negatively, correlated with EBPRT and EBFAT gain in repleted animals. Unlike IGF-I, IGF-II was not correlated with compensatory body growth. These results suggest that compensating steers are more metabolically efficient; rapid body tissue gain occurs during a period of reduced nutrient digestibility. Additionally, plasma levels of IGF-I, GH, INS, and thyroid hormones, but not of IGF-II, are markedly affected by alteration of energy intake and are highly correlated with empty body gain and protein deposition in compensating late-maturing steers.
选用18头契安尼娜杂交阉牛，在为期88天的对照再饲喂期（REAL；根据个体体重每周调整干物质采食量）内，研究激素状态与空体蛋白（EBPRT）和脂肪（EBFAT）沉积之间的相互关系。通过监测内源性全身40[K]来测定体成分。在限饲期（REST）结束时以及REAL期的第31天和第59天采集血样，分析生长激素（GH）、胰岛素样生长因子-I（IGF-I）、胰岛素样生长因子-II（IGF-II）、胰岛素（INS）、甲状腺素（T4）、三碘甲状腺原氨酸（T3）、反三碘甲状腺原氨酸（rT3）、非酯化脂肪酸（NEFA）、葡萄糖和尿素氮的浓度。与非限饲（NR）对照相比，限饲（92天）动物的EBPRT和EBFAT沉积减少（P < 0.001）。在限饲期间，血浆葡萄糖、IGF-I、INS、T4、T3和rT3水平降低（P < 0.05）；血浆尿素氮（PUN）、NEFA和GH水平升高（P < 0.05），限饲阉牛与NR阉牛之间的IGF-II浓度相似。在REAL期第35天至62天期间，再饲喂阉牛的体重增加和蛋白质沉积出现短暂的代偿性反应。在此期间，REAL阉牛的PUN水平显著下降（P < 0.01），葡萄糖浓度升高（P < 0.01）至与NR对照相似的水平。即使再饲喂动物的表观可消化养分减少，这种反应仍然存在。在能量再饲喂期间，再饲喂动物血浆中T4、T3、rT3、IGF-I和INS水平与EBPRT和EBFAT增加呈正相关，而GH水平与之呈负相关。与IGF-I不同，IGF-II与代偿性体生长无关。这些结果表明，代偿阉牛的代谢效率更高；在养分消化率降低的时期，体组织快速增加。此外，能量摄入的改变对血浆IGF-I、GH、INS和甲状腺激素水平有显著影响，但对IGF-II水平无显著影响，且这些激素水平与代偿性晚熟阉牛的空体增重和蛋白质沉积高度相关。
