271 EFFECT OF BULL ON IN VITRO FERTILIZATION OF BOVINE OOCYTES

Abstract

The main objective of this work was to evaluate the effect of the bull on IVF of bovine oocytes. These oocytes were obtained from ovaries collected in the slaughterhouse and selected for their maturation process in TCM-199 culture medium with 20% estrus cow serum, 10 IU of eCG, and 1 mg mL^-1 gentamicin. The oocytes were cultivated for 20 to 24 hours in 39.0°C culture incubator and moist environment with 5% CO₂. For the oocyte insemination, frozen/thawed semen of 8 bulls was used by means of swim-up capacity procedure according to Parrhit (1989) and then motility, sperm concentration, and strengh were evaluated. In all cases, 25 to 30 oocytes, previously selected according to cumulus oophorus density were artificially inseminated with 1 × 10⁶ spermatozoids mL_-1. The total of selected oocytes by bull for this work was: 5028 (1), 1247 (2), 2888 (3), 650 (4), 1529 (5), 699 (6), 984 (7), and 1250 (8). The results were evaluated according to the average of oocytes matured in vitro and to embryonic division 48 hours after AI. In order to evaluate the effects by bull, the statistical examination of chi-square proportion comparison was used. The average values and standard deviation (SD) motility were 57.0% ± 13.7; 53.2% ± 11.3; 51.2% ± 8.20; 40.9% ± 5.0; 48.1% ± 4.92; 33.5% ± 4.42; 53.5% ± 11.1 and 40.0% ± 8.9 for bulls 1 to 8, respectively. There was a highly significant difference (P < 0.001) in relation to the percentage of division: 46, 42, 34, 18, 30, 31, 30, and 17% among bulls 1 to 8, respectively, in addition to variability among these bulls. The results obtained confirm the effect of the bull on conception rate. The conclusion is that frozen/thawed semen with 50% motility can increase the percentage of embryonic division.