Fair S, Hanrahan J P, O'Meara C M, Duffy P, Rizos D, Wade M, Donovan A, Boland M P, Lonergan P, Evans A C O
Department of Animal Science, Centre for Integrative Biology, Conway Institute for Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
Theriogenology. 2005 Apr 15;63(7):1995-2005. doi: 10.1016/j.theriogenology.2004.09.005.
Ewe breed has been shown to have a major effect on pregnancy rates following cervical AI using frozen-thawed semen. The main objective of this study was to examine the differences between purebred Belclare and Suffolk ewes (multiparous) in fertilization rate, number of accessory sperm and stage of embryo development on day 6 after cervical or laparoscopic AI with frozen-thawed semen. In experiment 1, Belclare and Suffolk ewes were synchronized for 12 days and were either cervically inseminated (year 1: n=28 and 31; year 2: n=16 and 15, respectively) or laparoscopically inseminated (year 2: n=13 and 14). In experiment 2, superovulated Belclare (n=4) and Suffolk (n=13) ewes were laparoscopically inseminated. All ewes were slaughtered 6 days after AI; oocytes/embryos were recovered, morphologically graded and stained to assess the number of cells and accessory spermatozoa. Data from both experiments were combined for statistical analysis. The proportion of ewes with fertilized oocytes was significantly higher following laparoscopic AI compared with cervical AI (54% versus 19%). More Belclare than Suffolk ewes yielded fertilized oocyte(s) after cervical AI (34% versus 10%, P<0.02) but there was no difference after laparoscopic AI (62% versus 60%). From the ewes that yielded at least one fertilized oocyte the proportion of Belclare ewes with embryos at the morula/blastocyst stage was significantly greater than for Suffolk ewes (94% versus 59%, P<0.02). A higher proportion of Belclare than Suffolk ewes had evidence of sperm reaching the site of fertilization following cervical AI (39% versus 15%, P<0.02) but there was no difference after laparoscopic AI (62% versus 64%, P>0.8). Amongst the ewes with evidence of sperm at the site of fertilization, laparoscopic AI resulted in a higher number of sperm per oocyte/embryo or per ewe than cervical AI (P<0.01). These results suggested that the difference in pregnancy rate between Suffolk and Belclare ewes following cervical AI was due to: (i) sperm traversing the cervix and uterus in a higher proportion of Belclare than Suffolk ewes, leading to a higher incidence of fertilization and (ii) the lower developmental competence of fertilized oocytes from Suffolk ewes.
已证实母羊品种对使用冻融精液进行子宫颈人工授精后的妊娠率有重大影响。本研究的主要目的是检查纯种贝尔克莱羊和萨福克母羊（经产母羊）在使用冻融精液进行子宫颈或腹腔镜人工授精后第6天的受精率、附属精子数量和胚胎发育阶段的差异。在实验1中，使贝尔克莱羊和萨福克母羊同期发情12天，然后分别进行子宫颈授精（第1年：n = 28和31；第2年：n = 16和15）或腹腔镜授精（第2年：n = 13和14）。在实验2中，对超排的贝尔克莱羊（n = 4）和萨福克羊（n = 13）进行腹腔镜授精。所有母羊在人工授精后6天屠宰；回收卵母细胞/胚胎，进行形态学分级并染色以评估细胞数量和附属精子。将两个实验的数据合并进行统计分析。与子宫颈人工授精相比，腹腔镜人工授精后受精卵母细胞的母羊比例显著更高（54%对19%）。子宫颈人工授精后，产生受精卵母细胞的贝尔克莱母羊比萨福克母羊更多（34%对10%，P<0.02），但腹腔镜人工授精后无差异（62%对60%）。在至少产生一个受精卵母细胞的母羊中，处于桑椹胚/囊胚阶段胚胎的贝尔克莱母羊比例显著高于萨福克母羊（94%对59%，P<0.02）。子宫颈人工授精后，有证据表明精子到达受精部位的贝尔克莱母羊比例高于萨福克母羊（39%对15%，P<0.02），但腹腔镜人工授精后无差异（62%对64%，P>0.8）。在有证据表明精子在受精部位的母羊中，腹腔镜人工授精导致每个卵母细胞/胚胎或每只母羊的精子数量高于子宫颈人工授精（P<0.01）。这些结果表明，萨福克母羊和贝尔克莱母羊在子宫颈人工授精后妊娠率的差异是由于：（i）与萨福克母羊相比，更高比例的贝尔克莱母羊精子穿过子宫颈和子宫，导致受精发生率更高；（ii）萨福克母羊受精卵母细胞的发育能力较低。
