138 Effect of different temperatures on invitro maturation rates on cattle oocytes

Abstract

Climate change represents a major stressful environmental condition that compromises the reproductive efficiency of animals. The temperature affects various components of the maturation processes in cattle oocytes, this includes disruptions of oocyte development and maturation. Therefore, the study aimed to compare the effects of different incubation temperatures (32.5, 33.5 34.5, 35.5, 36.5, 37.5, 38.5, 39.5, 40.5, 41.5, 42.5, and 43.5°C) on the maturation rate of cattle oocytes. Cattle ovaries were collected from a local abattoir and transported to the laboratory in thermo flask at 37°C. Oocytes were recovered from ovaries using the aspiration method and matured using 500 uL of TCM-199 medium supplemented with 10% fetal bovine serum, FSH, LH, and E2 covered with mineral oil. The maturation rate of oocytes was determined by the extrusion of the first polar body after 22h of IVM period. The total number of 80 oocytes were matured in each group and replicated 4 times. Data were analysed using GenStat® statistical program (VSN International). Comparisons were considered significantly different (P<0.05) using Fisher’s protected least significant difference test. The oocyte polar body extrusion at 32.5 (0±0), 33.5 (4.5±5.2), 34.5 (22.0±1.4), 35.5 (29.5±7.6), 36.5 (41.5±3.1), 37.5 (55.5±4.1), 38.5 (62.2±3.3), 39.5 (49.5±3.3), 40.5 (17.3±6.4), 41.5 (10.3±5.7), 42.5 (8.2±5.9), and 43.5°C (5.7±7.8) (P<0.05) was recorded. The highest percentages of oocytes with polar body extrusion were at 37.5°C (55.5±4.1) and 38.5°C (62.2±3.3) and differed significantly from all other treatment groups (P<0.05). Temperature lower than 37.5°C and higher than 39.5°C did not intensify oocyte polar body extrusion. We concluded that the temperatures of 37.5°C and 38.5°C were suitable for IVM of cattle oocytes with acceptable polar body extrusion rates compared with other temperatures.