The in vitro culture environment of cattle embryos can compromise the survival of developing embryos resulting in cell apoptosis. Detection of cell apoptosis is important for determining embryonic quality and reducing embryonic mortality in female animals prior to transfer. In this study the role of cell apoptosis on in vitro embryos was studied, with the focus on oocyte maturation and embryo production, caspase-3 activity and DNA fragmentation. Cow ovaries were collected from local abattoir and a total of 900 COCs were retrieved per week for the study over five-month period (six replicate/per experiments). COCs were randomly allocated to four incubation temperatures (39, 41, 42 and 43 ̊C) for polar body extrusion. Based on maturation results, two preferred temperatures (39 and 41 ̊C) were selected for maturation. Oocytes were subjected to normal subsequent embryonic conditions post maturation. Embryos produced from both maturation temperatures were then examined for embryonic development, caspase-3 activity and DNA fragmentation for evidence of apoptosis. No difference was (P<0.05) observed in embryonic development between oocytes matured at 39 ̊C and 41 ̊C respectively. Blastocysts produced at 39 ̊C showed significantly (P < 0.05) higher nuclei cells compared to those produced from 41 ̊C matured oocytes. A higher (P< 0.05) caspase-3 activity and DNA fragmentation were observed at (2-4 cell) and (≥ 8cell cell) embryos for 41 ̊C matured oocytes compared to 39 ̊C maturation group. A significantly higher caspase-3 activity and DNA fragmentation on blastocyst produced at 41 ̊C matured oocytes were also evident compared to those produced at 39 ̊C. Although embryos produced from oocytes matured at 41 ̊C showed similar developmental capacity to embryos from 39 ̊C, this study showed that a higher incidence of apoptosis can be expected in embryos produced from oocytes matured at a higher (41 ̊C) temperature than 39 ̊C.
Dissertation (MSc (Agric))--University of Pretoria, 2017.