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The aim of this study was to assess the application of a cryopreservation program to preserve two selected rabbit lines. One of them was selected by litter size at weaning, line V (Synthetic breed). The second, line R (synthetic breed), was selected by growth rate. In this study, embryos were collected, from donor does belonging to the 7th and 15th generations of lines R and V, respectively, were vitrified and were stored from 1992-1993. Those embryos from donor does belonging to the 17th and 21st generations of lines R and V respectively, were vitrified and sotred from 1998-1999. Embryo transfers were carried out in 1999. Morphologically normal embryos at the morulae stage were cryopreserved by vitrification in a 2.8 M dimethyl-sulfoxide + 3.5 M ethylene-glycol + 0.3 g x L(-1) bovine serum albumine in Dulbecco phosphate buffered saline solution. The main problem in the cryopreservation program was the low embryo production efficiency: significant differences were obtained in recovery efficiency between lines and line R showed the lowest proportion of donor does with 55% (at least 4 normal embryos) vs. 72% in line V. However, after transfer in recipient does of line V, the fertility rate at birth (81%), the rate of alive born by pregnant recipients (43%) and the number of males and does with offspring (9 to 18 different males, 12 to 32 females) enabled the different generations from each line to be re-established and studies on the selection process genetic gain to be developed.

The in vivo survival rate of rabbit morulae after vitrification in a mixture of dimethyl sulphoxide and ethylene glycol solution without protein supplement (WPS) was compared with two types of protein supplements: rabbit serum (RS) and bovine serum albumin (BSA). Significant differences were observed in the percentage of transferable embryos (undamaged embryos after devitrification, 80.4% versus 93.2 and 92.1%, WPS, BSA and RS, respectively, P < 0.05) and live born rate (40.9% versus 56.1%, WPS and BSA, respectively, P < 0.05). Non-significant differences were, however, observed in the percentages of implanted embryos at 12 days post-ovulation induction (56.7, 69.7 and 68.6%), post-implantation survival rate (82.3, 74.2 and 77.2%) and live born rate in pregnant does (54.6, 56.1 and 50.5%) with different vitrification media (RS, BSA and WPS). We conclude that rabbit embryos can be vitrified and stored using protein-free vitrification medium with moderate losses of viability.