Predictors of success of semen cryopreservation in chickens.

Semen cryopreservation is very important for the ex situ management of genetic diversity in birds but it is rarely used. This is partly because of the highly variable success rates, and this emphasizes the need for predictors of semen freezability. This study evaluated the ability of semen quality tests to predict the success rates of semen cryopreservation in chickens and the relationships between each test. Individual variations of in vitro quality tests of semen were compared to the fertility obtained with fresh and cryopreserved semen. The in vitro semen quality tests represented viability, integrity, motility (percentage of viable and morphologically normal cells (PVN); mass motility (MMOT) and different motion parameters including percentage of motile spermatozoa (PMOT)) and biophysical tests (OSM, resistance to osmotic stress; membrane fluidity (FLUID)). Different in vitro tests were significantly correlated between each other for fresh (MMOT, PVN and FLUID, many criteria of objective motility) and cryopreserved semen (MMOT, different objective motility parameters, PVN). Fertility was significantly correlated with PVN for fresh semen and PVN and different objective motility criteria for cryopreserved semen. Membrane fluidity, followed by PVN, PMOT and MMOT, measured on fresh semen samples was positively correlated with fertility obtained with cryopreserved semen. The combination of the first three tests explained 85% of the variability of fertility observed with cryopreserved semen. In conclusion, we showed that different in vitro tests of semen quality are of predictive value for the success rate of semen cryopreservation in the chicken, the most accurate being membrane fluidity.