Environment and medium volume influence in vitro fertilisation of pig oocytes.

Oviductal oocytes (n = 795) were obtained from ovulation-induced prepubertal gilts. In the first experiment, different parameters related to in vitro fertilisation (IVF) were compared in the presence and absence of cumulus matrix (which is shed with the oocytes at ovulation). The results show that the presence of this matrix is beneficial because the rates of fertilisation (69%) and monospermy (number of monospermic oocytes/total number of healthy mature oocytes; 42%), and the median number of spermatozoa per oocyte (1.52 +/- 0.06), were improved with respect to those obtained in its absence (54%, 22% and 2.33 +/- 0.08, respectively; p < 0.01). In the second experiment the effect of two different volumes of co-incubation medium (2 ml and 0.4 ml) on the same parameters of porcine IVF were compared. No significant differences between volumes were observed, except in the mean number of spermatozoa per oocyte and the percentage of dispermic oocytes.