Lemal D, Renaville R, Claes V, Ruelle L, Fabry J, Burny A, Underwood L E, Ketelslegers J M
Faculty of Agronomy, Gembloux, Belgium.
J Anim Sci. 1989 Oct;67(10):2715-23. doi: 10.2527/jas1989.67102715x.
Effects of daily injections of pituitary-derived bovine somatotropin (bST) for 6 wk were evaluated in 10 growing heifers and compared to 9 placebo-treated control animals. Bovine somatotropin was injected at 50 micrograms/kg BW each day. Body weight and growth, plasma concentrations of insulin-like growth factor I (IGF-I) and somatotropin (ST) were assessed. To measure plasma concentrations of IGF-I, we validated a RIA in which bovine plasma samples were extracted with acid-ethanol, a method that resulted in greater than 90% recovery of IGF-I. Average daily gain was similar during the first 4 wk of the experiment in both control and bST-treated groups; however, at the end of the experimental period (wk 4 and 6) ADG was greater (P less than .05) in bST-treated heifers (1.24 +/- .21 kg/d vs .75 +/- .25 kg/d). Plasma IGF-I from wk 2 to wk 6 were increased in bST-treated animals (452 +/- 97 ng/ml at wk 2; 683 +/- 106 ng/ml at wk 6) compared with controls (293 +/- 62 ng/ml at wk 2 (P less than .01) and 293 +/- 115 ng/ml at wk 6 (P less than .001). Moreover, ADG over the 6-wk experimental period was correlated with mean IGF-I concentrations determined over the same period (r = .55; P less than .01). As expected, mean plasma ST concentrations were increased in bST-injected animals from wk 1 to 6. Gel chromatographic profiles of bovine plasma exhibit a 150,000 molecular weight ST-dependent binding protein-IGF-I complex and a 30,000 molecular weight non-ST-dependent complex. This study validates a method for measuring IGF-I in cattle, and shows a positive relationship among IGF-I and ADG after ST treatment. No correlation, however, was found between plasma ST and growth performance.
对10头生长中的小母牛每日注射垂体来源的牛生长激素（bST），持续6周，评估其效果，并与9头接受安慰剂处理的对照动物进行比较。每天按50微克/千克体重注射牛生长激素。评估体重和生长情况、胰岛素样生长因子I（IGF-I）和生长激素（ST）的血浆浓度。为了测量IGF-I的血浆浓度，我们验证了一种放射免疫分析法（RIA），即用酸乙醇提取牛血浆样本，该方法使IGF-I的回收率超过90%。在实验的前4周，对照组和接受bST处理的组的平均日增重相似；然而，在实验期结束时（第4周和第6周），接受bST处理的小母牛的平均日增重更高（P<0.05）（1.24±0.21千克/天对0.75±0.25千克/天）。与对照组相比，接受bST处理的动物在第2周和第6周的血浆IGF-I升高（第2周时为452±97纳克/毫升；第6周时为683±106纳克/毫升），而对照组在第2周时为293±62纳克/毫升（P<0.01），第6周时为293±115纳克/毫升（P<0.001）。此外，6周实验期内的平均日增重与同期测定的平均IGF-I浓度相关（r=0.55；P<0.01）。正如预期的那样，从第1周到第6周，接受bST注射的动物的平均血浆ST浓度升高。牛血浆的凝胶色谱图谱显示出一种分子量为150,000的依赖ST的结合蛋白-IGF-I复合物和一种分子量为30,000的不依赖ST的复合物。本研究验证了一种测量牛IGF-I的方法，并显示了ST处理后IGF-I与平均日增重之间的正相关关系。然而，未发现血浆ST与生长性能之间存在相关性。
