The research work was undertaken to determine an effective fertilization medium, sperm separation method and sperm capacitating agent for optimum in vitro fertilization (IVF) rates of indigenous zebu cow oocytes. In experiment 1, tissue culture medium (TCM 199), Tyrode’s albumin lactate pyruvate (TALP) and Brackett and Oliphant (BO) medium were used as basic medium for IVF of oocytes of indigenous zebu cows. In experiment 2, three sperm separation methods namely centrifugation, swim up and percoll gradient methods were used for separation of motile and viable spermatozoa for IVF. In experiment 3, for capacitation of spermatozoa, IVF medium supplemented with the heparin, mixture of penicillamine, hypotaurine and epinephrine (PHE) or the combination of heparin with PHE were used for fertilization. In vitro culture (IVC) of presumptive zygotes was done in modified synthetic oviduct fluid (mSOF) medium using standard procedure 24 h after sperm-oocytes co-culture. The cleavage rate was determined to evaluate the efficacy of fertilization medium, sperm separation method and sperm capacitating agent 24 h after IVC. The cleavage rate was higher in oocytes fertilized in TALP (63.3%) than in TCM 199 (47.5%) (p < 0.05). The cleavage rate was higher in oocytes fertilized by spermatozoa separated by percoll gradient method (62.3%) than by centrifugation (51.6%) (p < 0.05). The cleavage rate of oocytes was higher when insemination was done with spermatozoa capacitated in TALP supplemented with heparin and PHE (61.3%) compared to control (40.9%) (p < 0.05). In conclusions, TALP based medium and percoll gradient sperm separation followed by capacitation with combination of heparin and PHE are suitable for IVF of indigenous zebu cow oocytes in Bangladesh.

Cryopreservation of oocytes by vitrification technique may contribute a lot in the field of reproductive biotechnology. The objectives of the present study were to evaluate the effectiveness of two cryo-devices for vitrification of immature oocytes of indigenous zebu cows. Slaughter house derived immature cumulus-oocyte-complexes (COCs) of cows were vitrified using 15% dimethyl sulphoxide (DMSO) as cryoprotective agent (CPA) with 0.5 mol sucrose in TCM 199 supplemented with 20% FBS. Vitrification of COCs was completed after immediate plunging of COCs loaded cryotop or French mini straw into the liquid nitrogen (LN2). Then the COCs containing cryotop or French mini straws were warmed in 0.25 mol sucrose and 20% FBS supplemented TCM 199 followed by in vitro culture in 50 μl droplets of bicarbonate buffered TCM 199 supplemented with 10% FBS, pyruvate, FSH and oestradiol for 24 hrs at 39°C with 5% CO2 in humidified air. After maturation culture, oocytes were denuded and examined under inverted microscope for presence of polar body as the indication of maturation. Denuded oocytes were also stained by whole mount technique using 1% orcein to examine the maturation by presence of MII chromosomes. The in vitro maturation rate was significantly (p<0.05) higher in oocytes vitrified and warmed using crytop (47.1±6.9%) than that of French mini straw (15.9±12.5%). Moreover, in vitro maturation rate was significantly (p<0.05) highe r in control oocytes (not vitrified) (84.5±14.2%) than that of vitrified oocytes. In conclusion, cryotop is better than French mini straw as cryo-device for vitrification of bovine immature oocytes

The objectives of the present study were to select an effective basic medium including its hormone and protein supplementation for IVM of oocytes of indigenous zebu cows. The ovaries of cows were collected from slaughter house and the follicular fluid was aspirated from 2 to 8 mm diameter follicles. The COCs with more than 3 cumulus cell layers and homogenous cytoplasm were selected for maturation. The oocytes were matured in media for 24 hrs at 39℃ with 5% CO2 in humidified air. The maturation of oocytes was evaluated by examining the presence of first polar body under microscope. An efficient basic medium was determined after culturing COCs in either TCM 199 or SOF medium in Experiment 1. An efficient hormone supplementation was determined after culturing COCs in either FSH or gonadotrophin supplemented TCM 199 in Experiment 2. An efficient protein supplementation was determined after culturing COCs in either FBS or Oestrous cow serum (OCS) supplemented TCM 199 in Experiment 3. The oocyte recovery rate per ovary was 3.35. The overall rate of IVM was 74.6%. The maturation rate was 75.5±3.9 and 62.2±20.2% in TCM and SOF medium, respectively (P>0.05). The maturation rate of oocytes was significantly higher (76.6±13.2%) in FSH supplemented medium than gonadotrphin supplemented counterpart (69.7±10.8%) (P<0.05). The maturation rates of oocytes were 81.7±12.9 and 85.7±12.7% in medium supplemented with FBS and OCS, respectively (P>0.05). In conclusions, both TCM 199 and SOF supplemented with either FBS or OCS, and FSH may be used as medium for IVM of indigenous zebu oocytes in Bangladesh.