Effect of cryopreservation of individual ejaculates on fertility in genetic resource chicken lines

The aim of this study was to confirm the suitability of a cryopreservation protocol in three phylogenetically divergent chicken lines on individual ejaculates of roosters. The experimental animals originated from three gene reserve lines. In two trials individual semen samples were cryopreserved and used in insemination experiments. For the freezing medium N-methylacetamide and dimethylformamide were mixed 2:1 in a base diluent according to Hanzawa et al. ( 2006). 0.25 ml straws were frozen in two phases beginning with a controlled temperature decrease of –3°C/min. The samples were thawed in a 4°C water bath. The semen was evaluated by means of CASA (computer-assisted sperm analysis). The hens were intravaginal inseminated in the distance of three or four days three times. Fertilization rate was determined after 7-day incubation by candling. Results showed a considerable influence of trial, chicken line and their interaction on sperm quality and fertility. Fertilization results with frozen sperm were extremely variable between individual roosters within the lines and trials (line R22: 9.7–73.3%, line G11: 33.3–84.6%, line L68: 41.4–87.5%). Significant correlations between sperm quality parameters and fertility rates were found only in two of three chicken lines. The results prove that there are genetic differences in the sperm quality and the subsequent fertility which should be taken into account at the construction of a sperm bank. But the developed cryopreservation method was applied successfully to individual roosters of genetic resource lines and is therefore eligible for gene banking of endangered chicken populations.