López-Gatius F, Santolaria P, Martino A, Delétang F, De Rensis F
Department of Animal Production, University of Lleida, Lleida, Spain.
Theriogenology. 2006 Mar 1;65(4):820-30. doi: 10.1016/j.theriogenology.2005.07.002. Epub 2005 Aug 19.
It was hypothesized that gonadotropin-releasing hormone (GnRH) treatment at the time of insemination and 12 days later increases conception rates. The aim of the present study was to evaluate the effects of GnRH treatment at the time of insemination or at the time of insemination and 12 days later on reproductive performance during the warm season in high producing dairy cows. The effect of GnRH treatment on the incidence of subsequent twin pregnancies and pregnancy losses was also evaluated. Data were analyzed using logistic regression methods. Of the entire series of 1289 AI, 373 (29%) resulted in pregnancy. Three study groups were established to evaluate the effects of treatment on the conception rate: control (untreated cows, n=431), GnRH-0 (cows receiving GnRH at AI, n=429) or GnRH-0+12 (cows receiving GnRH at AI and at AI+12 days, n=429). Conception rates were 20.6% (89/431), 30.8% (132/429) and 35.4% (152/429) for animals receiving no treatment, GnRH at AI, and GnRH at AI and 12 days later, respectively. Based on the odds ratio, the probability of pregnancy was 0.80 and 0.46 times less likely for cows receiving treatment GnRH-0 and no treatment, respectively, than for cows receiving treatment GnRH-0+12 (reference). Of the 373 pregnant animals, 326 (87.4%) bore singletons and 47 (12.6%) carried twins. The effects of treatment on the dependent variables: twin pregnancy, additional corpus luteum and pregnancy loss were analyzed. Pregnancy loss between 38 and 90 days after insemination was registered in 30 (8%) cows: 17 (5.2%) in single and 13 (27.7%) in twin pregnancies. Fifty-six (15%) cows had an additional corpus luteum. No pregnancy losses were recorded in these cows. Treatment had no effect on the twin pregnancy rate. The treatment GnRH at AI and 12 days later increased the chances of an additional corpus luteum by a factor 3.7 (using the control group as reference). In conclusion, our results support the hypothesis that GnRH treatment at the time of insemination and 12 days later increases the conception rate in high producing dairy cows during the warm season. Although lower than double treatment, strong benefits were also registered following a single GnRH treatment at insemination. Under these conditions, treatment fails to affect the twin pregnancy rate yet increases the incidence of an additional corpus luteum in pregnant cows.
研究假设，在授精时及12天后进行促性腺激素释放激素（GnRH）治疗可提高受孕率。本研究的目的是评估在高产奶牛的温暖季节，授精时或授精时及12天后进行GnRH治疗对繁殖性能的影响。还评估了GnRH治疗对随后双胎妊娠发生率和妊娠丢失的影响。使用逻辑回归方法分析数据。在总共1289次人工授精中，373次（29%）成功受孕。设立了三个研究组来评估治疗对受孕率的影响：对照组（未治疗的奶牛，n = 431）、GnRH-0组（授精时接受GnRH治疗的奶牛，n = 429）或GnRH-0 + 12组（授精时及授精后12天接受GnRH治疗的奶牛，n = 429）。未接受治疗、授精时接受GnRH治疗以及授精时及12天后接受GnRH治疗的动物的受孕率分别为20.6%（89/431）、30.8%（132/429）和35.4%（152/429）。根据优势比，与接受GnRH-0 + 12治疗的奶牛（参照组）相比，接受GnRH-0治疗和未接受治疗的奶牛怀孕的概率分别低0.80倍和0.46倍。在373头怀孕动物中，326头（87.4%）产下单胎，47头（12.6%）怀有双胎。分析了治疗对以下因变量的影响：双胎妊娠、额外黄体和妊娠丢失。授精后38至90天内，30头（8%）奶牛出现妊娠丢失：单胎妊娠中17头（5.2%），双胎妊娠中13头（27.7%）。56头（15%）奶牛有额外黄体。这些奶牛未记录到妊娠丢失。治疗对双胎妊娠率没有影响。授精时及12天后进行GnRH治疗使出现额外黄体的几率增加了3.7倍（以对照组为参照）。总之，我们的结果支持以下假设：在温暖季节，授精时及12天后进行GnRH治疗可提高高产奶牛的受孕率。虽然低于双重治疗，但在授精时单次进行GnRH治疗也有显著益处。在这些条件下，治疗未能影响双胎妊娠率，但增加了怀孕奶牛出现额外黄体的发生率。
