EFFECT OF MEDIUM-199 AND FETAL CALF SERUM ON IN-VITRO MATURATION OF DOMESTIC CAT OOCYTES

In vitro maturation (IVM) and fertilization are potentially useful for propagating threatened or endangered species. The domestic cat is cur rently used in this field as an experimental model for studies aimed a t non-domestic Felidae. At present optimal conditions for obtaining IV M of cat oocytes have not yet been completely defined. The aim of this study was to evaluate two parameters derived from the procedures that currently ensure high maturation rates in domestic ruminants: (1) the suitability of a complex medium (M-199) for IVM of cat oocytes; (2) t he effect of different concentrations of fetal calf serum in the cultu re medium with or without the addition of gonadotrophins. The maturati on rate at two different intervals from the onset of culture (24 and 4 8 h) was also evaluated. The use of M-199 allowed resumption of meiosi s in 4.3-18.7% of cat oocytes, according to the supplements and cultur e periods used. No significant differences were recorded among the tre atment groups (P > 0.05). Meiosis was completed in 90.9% of cases with in 24 h with no significant differences between the three treatment gr oups (P > 0.05). A 3-2% rate of parthenogenesis was observed at the en d of the maturation period with no significant differences between the culture systems (P > 0.05). However, the percentage cleavage of oocyt es was much higher (29%) when correlated with the percentage that had matured. In this case significant differences among treatments were al so observed (P < 0.05). It is concluded that the use of a complex medi um supplemented with serum supports the ability of cat oocytes to resu me meiosis in vitro, but overall results are still lower than those ob tained in farm animal species and in the cat using simple media. These results suggest that fetal calf serum at high rates is detrimental to resumption of meiosis but this negative effect is at least partially counteracted by the presence of gonadotrophins. In the system describe d here, full maturation was usually achieved within the first 24 h of culture. A high incidence of parthenogenesis was noted.