In vitro maturation of oocytes retrieved through transvaginal oocyte aspiration from Boran and Boran *Holstein Friesian crossbred cows
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Date
2021
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Addis Ababa University
Abstract
The developmental competence of immature oocytes largely depends on the origin and method of retrieval. This is known to determine the success of in vitro embryo production. This study aimed to evaluate the in vitro maturation difference of oocytes from pure Boran and Holstein Friesian*Boran crossbred cows obtained through ovum pickup. The OPU was carried out on 10 cows, 5 cows from each breed. The overall oocyte recovery rate was 43.4% (288/663); 39.3% (131/333) for Boran and 47.6% (157/330) for Crossbred with no breed influence (p>0.05). Oocytes aspirated from the 288 follicles (all ≥ 3mm) were matured in either TCM-199 or BO-IVM maturation mediums. Proportion of viable oocytes were comparable between Boran (81.60%) and B*HF crossbred (78.9%). The mean number of oocytes collected per ovum pickup session for Boran and Crossbred cows were 2.18 ± 1.90 and 2.62 ± 1.86, respectively. The overall maturation rate was in the order of 79.4% and 79% for Boran and crossbreeds, respectively, and comparable between the breeds. Considering all maturation indices, oocyte maturation was significantly higher (p<0.05) in BO-IVM (88.5%) compared to TCM-199 (70.4%). Maturation of Boran oocytes in BO-IVM was relatively higher (90.3%) compared to Boran*HF oocytes (86.2%); whereas it was 73.1% for Boran and 68.2% for Boran*HF oocytes in TCM. Maturation rate in terms of cumulus cell expansion was relatively better in BO-IVM (59.3% fully expanded and 30.1% partially expanded) compared to TCM-199 (46.9% fully expanded and 24.4% partially expanded). Overall, there was extrusion of the polar body in 55.75% of oocytes and increased perivitelline space in 69.2% of oocytes. Zona quality was relatively better in BO-IVM (69.2% of oocytes) compared to TCM-199 medium (60.9% of oocytes). In conclusion, oocyte maturation following OPU was influenced by media type but not by breed. It can also be concluded that some of the maturation indices were more affected by breed and media type even though the overall maturation was closely similar.
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Boran crossbreed, in vitro, maturation, oocytes