EFFECTS OF GENOTYPE AND CRYOPRESERVATION OF AVIAN SEMEN ON FERTILITY AND NUMBER OF PERIVITELLINE SPERMATOZOA

1. The fertility of freshly diluted and cryopreserved samples of semen obtained from a population of chickens selected for duration of ferti lity of cryopreserved spermatozoa (FS line) and its unselected control (FC line) were compared over a range of spermatozoa concentrations (1 0, 40, 80, and 160 x 10(6) sperm/50 mul insemination). 2. The spermato zoa of the FS line had greater fertility than spermatozoa of the FC li ne, whether freshly diluted or cryopreserved. Cryopreservation resulte d in a reduction in fertility, regardless of line. There were no signi ficant line by genotype interactions. 3. There were fewer spermatozoa from the FC line than the FS line found in the perivitelline membrane (perivitelline spermatozoa). The increase in number of perivitelline s permatozoa with increasing sperm concentration was greater in the FS t han FC line. However, the slope of the increase in sperm number in the perivitelline membrane with increasing concentrations of cryopreserve d spermatozoa was zero. 4. A minimum of 10(3) perivitelline spermatozo a must be found on day 2 post-insemination for duration of fertility t o exceed three days. The ability to produce spermatozoa capable of rea ching the forming perivitelline membrane appears to be a quantitative, rather than a qualitative, trait and may be subject to genetic manipu lation.