Stevenson J S, Call E P, Scoby R K, Phatak A P
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506.
J Dairy Sci. 1990 Jul;73(7):1766-72. doi: 10.3168/jds.S0022-0302(90)78855-8.
Our objective was to determine if double inseminations during the same estrous period of dairy cattle eligible for their third or fourth service (repeat breeders) would improve pregnancy rates equivalent to injections of GnRH given at the time of AI. Repeat-breeding, lactating cows from six herds (five herds in the San Joaquin Valley of central California and one herd in northeast Kansas) were assigned randomly to four treatment groups when detected in estrus: 1) single AI plus no injection, 2) single AI plus 100 micrograms GnRH at AI, 3) double AI plus no injection, or 4) double AI plus 100 micrograms of GnRH at AI. Inseminations were performed according to the a.m.-p.m. rule. The second AI for the double AI treatment was given 12 to 16 h after the first AI. Injections of GnRH were given intramuscularly immediately following the single AI or the first AI of the double AI. Pregnancy rates of cows given a single AI and hormone injection were numerically higher in all six herds than those of their herdmates given only a single AI. In five of six herds, the pregnancy rates of cows given a double AI and hormone injection were numerically higher than pregnancy rates of their herdmates given only a double AI. Overall pregnancy rates for the four treatments were 1) 112/353 (32.1%), 2) 165/406 (41.6%), 3) 119/364 (33.5%), and 4) 135/359 (37.5%). Gonadotropin-releasing hormone increased pregnancy rates of repeat breeders compared with controls given only a single AI. No further benefit beyond the single AI was accrued from the double AI treatment, with or without concurrent hormone administration.
我们的目标是确定，对于符合第三次或第四次输精条件（屡配不孕牛）的奶牛，在同一发情期进行两次输精是否能提高妊娠率，使其与在人工授精（AI）时注射促性腺激素释放激素（GnRH）的效果相当。来自六个牛群（加利福尼亚中部圣华金谷的五个牛群和堪萨斯州东北部的一个牛群）的屡配不孕泌乳奶牛在发情期被检测到时，被随机分配到四个处理组：1）单次人工授精且不注射，2）单次人工授精加在人工授精时注射100微克GnRH，3）两次人工授精且不注射，或4）两次人工授精加在人工授精时注射100微克GnRH。输精按照上午-下午规则进行。两次人工授精处理中的第二次人工授精在第一次人工授精后12至16小时进行。在单次人工授精或两次人工授精的第一次人工授精后，立即肌肉注射GnRH。在所有六个牛群中，接受单次人工授精和激素注射的奶牛的妊娠率在数值上高于仅接受单次人工授精的同群奶牛。在六个牛群中的五个牛群中，接受两次人工授精和激素注射的奶牛的妊娠率在数值上高于仅接受两次人工授精的同群奶牛。四种处理的总体妊娠率分别为：1）112/353（32.1%），2）165/406（41.6%），3）119/364（33.5%），4）135/359（37.5%）。与仅接受单次人工授精的对照组相比，促性腺激素释放激素提高了屡配不孕牛的妊娠率。无论是否同时给予激素，两次人工授精处理在单次人工授精之外没有带来进一步的益处。
