Summary. Cumulus–oocyte complexes, 5596, were cultured for 24 h in either TCM-199 or Ham's F-10 with or without gonadotrophins and supplemented with either 20% buffalo oestrous serum (BES) or fetal calf serum (FCS). The maturation rates of oocytes cultured in TCM-199 or Ham's F-10 medium supplemented with 20% BES were 47·4 ± 17·8 and 44·8 ± 25·6, respectively. Addition of luteinizing hormone (LH) (5 μg ml−1) significantly improved the maturation rate in the Ham's F-10 medium supplemented with 20% BES (76·8 ± 18·3), but follicle-stimulating hormone (FSH) (0·5 μg ml−1) and oestradiol (1 μg ml−1) failed to synergize with LH (71·7 ± 19·5). In the TCM-199 system, LH failed to enhance the maturation rate but the addition of FSH and oestradiol significantly enhanced the proportion of mature oocytes (42·7 ± 1·4 and 81·7 ± 14·5, respectively; P < 0·05). Frozen–thawed spermatozoa prepared in Bracket and Oliphant (BO) medium and treated with 5 mmol caffeine l−1 ± 10 μg heparin showed a higher fertilization rate (29·8%) than those treated in Hepes–Talp and treated with 10 μg heparin ml−1 (19·6%). Fertilization rate was significantly improved when fresh ejaculated spermatozoa treated with 5 mmol caffeine l−1 and 10 pg heparin in BO medium (50%) was used. Rate of cleavage and development were also higher when in vitro fertilization was carried out with fresh ejaculated spermatozoa treated with caffeine and heparin (34·1 and 36·8%, respectively) than with frozen–thawed spermatozoa (27·0 and 22·0%, respectively).
Development rate was enhanced when fertilized ova were cultured in ligated rabbit oviduct (28·0%) than when co-cultured on oviductal cell monolayers (8·2%). The results indicate that oocytes cultured in medium supplemented with BES and gonadotrophins reveal high rates of maturation and development to the blastocyst stage after fertilization with fresh ejaculated spermatozoa.
Keywords: oocytes; maturation; fertilization; culture; buffalo