Heritability of Fertility of Frozen and Fresh Chicken Semen and the Relationship Between the Fertility of Frozen and Fresh Semen

A broiler type male line, which is under selection for duration of fertility of frozen semen, was used. For freezing semen glycerol was the cryopreservative and fertility was based on the insemination of five hens per ejaculate. The mean and standard deviation for duration of fertility (days), percent fertility during the duration and percent hens fertile were: (1) from frozen semen in generation one 1.04 ± 3.6, 21.6 ± 22.0, 31.8 ± 28.6; (2) from frozen semen in generation two 0.86 ± 1.24, 14.7 ± 13.48 and 16.8 ± 20.8, and (3) from fresh semen in generation two 8.60 ± 3.60, 69.0 ± 24.1, 86.0 ± 25.7, respectively. Heritabilities were calculated for each fertility trait of frozen semen based on the sire component in generation one, and in generation two on the sire, dam and sire plus dam components for the fertility of frozen and fresh semen and by sire offspring regression for fertility of frozen semen. Based on regression, the heritabilities for fertility of frozen semen were 0.12 ± 0.07 for duration of fertility, 0.09 ± 0.08 for percent fertility during the duration and 0.16 ± 0.11 for percent hens fertile. For fertility of fresh semen the sire and dam components of variance were negative in all cases except the dam component for duration of fertility where the heritability was 0.32 ± 0.02. All estimates of fertility within fresh and frozen semen were highly significantly positively phenotypically correlated but the fertility of fresh and frozen semen were not correlated. Similarly, breeding values, as calculated for each male for each trait were highly significantly positively correlated within fresh or frozen semen but not between fresh and frozen semen. There was some suggestion that the breeding values between fresh and frozen semen may be negatively associated.