Comparison of cryoprotectants and methods of cryopreservation of fowl spermatozoa

The deleterious effects of three cryoprotectants, glycerol, dimethylsulfoxi de (DMSO), and dimethylacetamide (DMA), were compared on fowl spermatozoa. The viability and integrity of spermatozoa were measured with eosin-nigrosi n smears. Glycerol was the least deleterious cryoprotectant, followed by DM A, and DMSO was the most toxic. Methods employing either glycerol or DMA we re then compared for the cryopreservation of semen in either straws or pell ets. Fertility was measured following artificial insemination. The highest fertility rates were obtained with semen frozen with DMA in pel lets directly plunged in liquid nitrogen, DMA being added at -6 C (92.7%) o r 5 C (84.7%). When semen was frozen in straws, glycerol equilibrated for 1 or 30 min gave the highest fertility results, but the fertility rates were lower (53.7 and 63.9%) than with DMA in pellets. The lowest results (26.7% ) were obtained when semen was frozen in straws with DMA. When semen was frozen in pellets at very high cooling rates, DMA was superi or to glycerol as a cryoprotectant, as evidenced by fertility. In contrast, when straws and low freezing rates were used, glycerol gave better results ; however these results were never as high as those obtained with DMA and p ellets. Ln conclusion, under our experimental conditions, the highest ferti lity rates were achieved with DMA and pellets. However, for gene banking, w hich requires high levels of safety and clear identification, glycerol and straws are more convenient.