Hill G M, Richardson K L, Utley P R
University of Georgia, Tifton 31793-0748.
J Anim Sci. 1988 Oct;66(10):2435-42. doi: 10.2527/jas1988.66102435x.
In dose titration trials beef heifers received depot-formulated melengestrol acetate (DEPO-MGA) in single s.c. ear injections to determine effects on performance and pregnancy inhibition. In a 112-d feedlot trial, 105 heifers were assigned to light, medium and heavy weight blocks on five treatments: dietary MGA (.5 mg.hd-1.d-1), control (no MGA) or DEPO-MGA on d 1 at .5, 1.0 or 1.5 ml/hd (30, 60 or 90 mg MGA/hd, respectively). A high-energy cracked corn diet was fed to all heifers ad libitum. At d 56 and d 112, ADG and feed/gain were not affected (P greater than .05) by dietary MGA or DEPO-MGA treatments, although dietary MGA tended to increase 112-d ADG (1.67 vs 1.58 kg) compared with controls. In a pasture trial, 100 beef heifers were assigned by weight to five treatments: control (no MGA) or DEPO-MGA injected on d 1 at .5, 1.0, 1.5 or 2.0 ml/hd (30, 60, 90 or 120 mg MGA/hd, respectively). Heifers were pastured as a single herd and were exposed to fertile bulls from d 7 to d 181. Weights and pregnancy data were recorded at d 62, 90, 134, 181 and 225. Heifer ADG was not affected (P greater than .05) by DEPO-MGA treatment at any weighing date. By d 90, 90% of control heifers were pregnant, and 100% were pregnant by d 134. Pregnancy inhibition rates of 90% to 100% for each DEPO-MGA treatment at d 62, 90 and 134 were higher (P less than .01) than those in control heifers. Pregnancy was inhibited in 90% of heifers on 60-mg and 90-mg DEPO-MGA treatments through d 181, and in 95% of heifers on the 120 mg DEPO-MGA treatment through d 225.
在剂量滴定试验中，肉用小母牛通过耳后单次皮下注射接受长效醋酸甲地孕酮（DEPO - MGA），以确定其对生产性能和抑制怀孕的影响。在一项为期112天的饲养场试验中，105头小母牛按体重分为轻、中、重三组，接受五种处理：日粮添加甲地孕酮（0.5毫克/头·天）、对照（不添加甲地孕酮）或在第1天注射DEPO - MGA，剂量分别为0.5、1.0或1.5毫升/头（分别相当于30、60或90毫克甲地孕酮/头）。所有小母牛自由采食高能碎玉米日粮。在第56天和第112天，日粮中添加甲地孕酮或DEPO - MGA处理对平均日增重（ADG）和料重比没有影响（P＞0.05），不过与对照组相比，日粮添加甲地孕酮使第112天的ADG有增加趋势（1.67千克对1.58千克）。在一项牧场试验中，100头肉用小母牛按体重分为五种处理：对照（不添加甲地孕酮）或在第1天注射DEPO - MGA，剂量分别为0.5、1.0、1.5或2.0毫升/头（分别相当于30、60、90或120毫克甲地孕酮/头）。小母牛作为一个群体放牧，并在第7天至第181天接触可育公牛。在第62、90、134、181和225天记录体重和怀孕数据。在任何称重日期，DEPO - MGA处理对小母牛的ADG均无影响（P＞0.05）。到第90天，90%的对照小母牛怀孕，到第134天全部怀孕。在第62、90和134天，各DEPO - MGA处理的怀孕抑制率为90%至100%，高于对照小母牛（P＜0.01）。在第181天，60毫克和90毫克DEPO - MGA处理的小母牛中有90%怀孕受到抑制，在第225天，120毫克DEPO - MGA处理的小母牛中有95%怀孕受到抑制。
