A COMPARISON OF MENEZOS B2 AND TISSUE-CULTURE MEDIUM-199 FOR IN-VITROPRODUCTION OF BOVINE BLASTOCYSTS

The objectives of this study were, first, to evaluate the effectivenes s of 2 culture media, Menezo's B2 (B2) and Tissue Culture Medium-199 ( M-199), for the production of bovine blastocysts in a commercial embry o transfer program; and, second, to characterize the stage of developm ent, quality grade and cell number of blastocysts produced in each med ium. One-cell bovine embryos were produced using in vitro maturation a nd fertilization procedures. After fertilization, the embryos were co- cultured on Buffalo rat liver (BRL) cell monolayers in either B2 or M- 199+1% BSA (M-199) medium. Both media were supplemented with 10% fetal calf serum (FCS) and penicillin/streptomycin. Embryo cultures were co ntinued undisturbed to either Day 7 or Day 8 post-insemination, In the Day 7 cultures, all blastocysts were removed for evaluation on Day 7, and the remaining embryos were cultured for a further 24 h. Any addit ional blastocysts that formed were removed for evaluation and designat ed as Day 8 disturbed embryos. All blastocysts were classified for sta ge and quality grade. Embryos were fixed and stained for determination of cell number. Overall, the proportion of blastocysts was greater (P =0.0003) with B2 medium (46%) than with M-199 (33%). This was due to a larger (P=0.0001) proportion of blastocysts produced in B2 medium whe n cultures were left undisturbed for 8 d (50 vs 28% for B2 vs M-199). The proportion of blastocysts on Day 7 of culture tended to differ (P= 0.073) between media (33 vs 24% for B2 vs M-199). In addition, there w ere more (P=0.007) blastocysts at advanced stages of development in B2 medium on Day 7. There was no effect of type of medium on the distrib ution of embryo quality grades on any day examined. The number of cell s per blastocyst did not differ between media but did Vary significant ly (P<.05) with both stage and grade. In conclusion, B2 medium was sup erior to M-199 medium when used in a coculture system with BRL cells f or the production of bovine blastocysts. (C) 1997 by Elsevier Science Inc.