Henricks D M, Edwards R L, Champe K A, Gettys T W, Skelley G C, Gimenez T
J Anim Sci. 1982 Nov;55(5):1048-56. doi: 10.2527/jas1982.5551048x.
Twenty-four heifers were allotted into three groups of eight heifers each and designated control, long-term (LT) or short-term (ST). Animals in the latter two groups were implanted in the ear with 300 mg trenbolone acetate (TBA) for 99 or 62 d, respectively. Four heifers in each group were subjected to liver and fat biopsy 60 d after initiation of the experiment. At slaughter, which occurred 15 d after retrieval of the implant, liver and fat were also collected. The implant was analyzed for residual trenbolone (TBOH), and tissues were analyzed for TBOH and estradiol-17 beta (E2 beta). Blood samples were taken weekly after implantation and daily for 14 d before and after implantation. All heifers were weighed weekly. The ST heifers gained faster (P less than .05) than the control or the LT heifers, whereas the LT heifers gained similarly to the controls. Plasma levels of TBOH rose to over 900 pg/ml in response to the implantation in both treated groups, but stabilized at a lower level in the ST group than in the LT group. In both groups plasma E2 beta rose to over 7.5 pg/ml in response to TBA implantation; in fact, a regression analysis of E2 beta on TBOH in individual cows showed that the two hormones varied directly. Fat and liver accumulated substantial TBOH during implantation, but it cleared rapidly during the 15 d withdrawal period. Indications from this experiment are that TBA has promise for promoting rate of gain and efficiency of feed utilization in feedlot heifers. No undesirable effects on carcass quality were detected. The drug cleared blood and tissues rapidly after the implant was withdrawn. Further research is needed to determine the most effective implantation schedule. It would be desirable to determine whether a positive response to TBA will occur in animals being finished predominantly on forages.
24头小母牛被分成三组，每组8头，分别设为对照组、长期（LT）组或短期（ST）组。后两组的动物分别在耳朵中植入300毫克醋酸群勃龙（TBA），时长分别为99天或62天。每组中的4头小母牛在实验开始60天后进行肝脏和脂肪活检。在植入物取出15天后进行屠宰，同时收集肝脏和脂肪。分析植入物中的残留群勃龙（TBOH），并分析组织中的TBOH和雌二醇-17β（E2β）。植入后每周采集血样，植入前后各14天每天采集血样。所有小母牛每周称重。ST组小母牛的生长速度比对照组或LT组更快（P<0.05），而LT组小母牛的生长速度与对照组相似。两个处理组植入后血浆TBOH水平均升至900 pg/ml以上，但ST组稳定在比LT组更低的水平。两组中，血浆E2β因TBA植入而升至7.5 pg/ml以上；事实上，对个体奶牛中E2β与TBOH的回归分析表明，这两种激素呈正相关。植入期间脂肪和肝脏积累了大量TBOH，但在15天的停药期内迅速清除。该实验表明，TBA有望提高育肥牛的生长速度和饲料利用效率。未检测到对胴体质量的不良影响。植入物取出后，药物迅速从血液和组织中清除。需要进一步研究以确定最有效的植入方案。确定在主要以草料育肥的动物中对TBA是否会产生阳性反应是很有必要的。
