Evaluation of cryopreservation techniques for goat embryos.

A total of 410 goat embryos were divided at random into 9 groups. Cryoprotectants (glycerol, ethylene glycol or dimethylsulfoxide) were added by a 3-step procedure using increasing concentrations of cryoprotectant (0.5 M; 1 M; 1.5 M) in PBS at 10 min intervals. After freezing and thawing, each cryoprotectant was removed by 3 methods: the classic 3-step procedure (cryoprotectant 1 M-10 min; 0.5 M-10 min; PBS alone-10 min); the same procedure, but with sucrose added to the first 2 steps (sucrose 0.25 M and cryoprotectant 1 M-10 min; sucrose 0.25 M and cryoprotectant 0.5 M-10 min; PBS alone-10 min); and a 2-step procedure with sucrose alone (sucrose 0.25 M-10 min; PBS alone-10 min). Each removal protocol was performed for embryos in each cryoprotectant. The viability of the embryo was evaluated by its capacity to subsequently develop during 48 h in vitro culture. For morulae the development rate of the embryos was significantly higher when they were frozen with ethylene glycol than when dimethylsulfoxide or glycerol was used (P < 0.05). For blastocysts the development rate was the same whether they had been frozen with ethylene glycol or dimethylsulfoxide, and was significantly lower when they were frozen with glycerol (P < 0.05). Among the 3 removal procedures tested, the 3-step procedure with sucrose gave the best development rate and differed significantly from the classic 3-step procedure (P < 0.05).