Granger A L, Wyatt W E, Craig W M, Thompson D L, Hembry F G
Department of Animal Science, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803.
Domest Anim Endocrinol. 1989 Jul;6(3):253-62. doi: 10.1016/0739-7240(89)90019-2.
Twenty-five Brangus (BR) and 15 Angus (AN) heifers were used to study the effects of breed and wintering diet on average daily gain (ADG), onset of puberty and plasma concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1). Wintering diets (fed for 107 days beginning November 15) consisted of the following: 1) native grass hay (NGH), 2) ammoniated NGH, 3) NGH plus cottonseed meal, 4) Diet 3 plus corn and 5) Diet 4 plus monensin. After wintering, heifers were transferred to ryegrass pasture for 70 days. Mean ADG during the wintering phase were -.20, -.10, .17, .29 and .39 kg for heifers fed Diets 1 through 5, respectively (P less than .01). ADG was greater (P less than .05) for BR than for AN heifers. Plasma concentrations of GH were higher (P less than .05) in heifers fed Diets 1 and 2 than in heifers fed Diets 3, 4 or 5. Plasma concentrations of IGF-1 were lowest in heifers fed Diet 1 and highest in heifers fed Diets 4 and 5. During ryegrass grazing, GH concentrations were similar for all groups. However, concentrations of IGF-1 were higher (P less than .05) in heifers fed Diets 3, 4 and 5 than in heifers fed Diets 1 and 2. Age at puberty (onset of cyclic progesterone concentrations) was greatest in heifers fed Diet 1 and lowest in heifers fed Diet 5. Weight at puberty was not affected (P greater than .10) by wintering diet but was greater (P less than .01) in BR than in AN heifers. Therefore, negative ADG appears to be associated with elevated plasma GH concentrations in heifers, and plasma IGF-1 concentration appears to be a more accurate indication of nutritional status than plasma concentrations of GH.
选用25头勃莱格斯（BR）小母牛和15头安格斯（AN）小母牛，研究品种和越冬日粮对平均日增重（ADG）、青春期启动以及生长激素（GH）和胰岛素样生长因子1（IGF-1）血浆浓度的影响。越冬日粮（从11月15日开始饲喂107天）包括以下几种：1）天然草地干草（NGH），2）氨化天然草地干草，3）天然草地干草加棉籽粕，4）日粮3加玉米，5）日粮4加莫能菌素。越冬期结束后，小母牛被转移到黑麦草牧场70天。饲喂日粮1至5的小母牛在越冬期的平均日增重分别为-.20、-.10、.17、.29和.39千克（P＜0.01）。BR小母牛的平均日增重高于AN小母牛（P＜0.05）。饲喂日粮1和2的小母牛血浆GH浓度高于饲喂日粮3、4或5的小母牛（P＜0.05）。饲喂日粮1的小母牛血浆IGF-1浓度最低，饲喂日粮4和5的小母牛血浆IGF-1浓度最高。在黑麦草放牧期间，所有组的GH浓度相似。然而，饲喂日粮3、4和5的小母牛血浆IGF-1浓度高于饲喂日粮1和2的小母牛（P＜0.05）。青春期年龄（循环孕酮浓度开始时）在饲喂日粮1的小母牛中最大，在饲喂日粮5的小母牛中最小。越冬日粮对青春期体重没有影响（P＞0.10），但BR小母牛的青春期体重高于AN小母牛（P＜0.01）。因此，小母牛的负平均日增重似乎与血浆GH浓度升高有关，血浆IGF-1浓度似乎比血浆GH浓度更能准确反映营养状况。
