Fertility in the male rabbit. III. Estimation of spermatozoan quality by mixed insemination and the inheritance of spermatozoan characters

Summary. (1) Variation in the quality of rabbit spermatozoa has been related to variation in the conception rate, gestation length, litter size, birth weight and mortality from birth to weaning, after homospermic and heterospermic insemination.(2) Heterospermic insemination with ten times the number of sperma¬ tozoa, as in homospermic insemination, gave a higher conception rate and litter size. The importance of spermatozoan quality and of the number of spermatozoa inseminated has been discussed in relation to heterospermic insemination.(3) The mean litter size was found to be related to the mean percentage capless spermatozoa and the mean spermatozoan head length of the sire. (4) The within-breed regression of the mean birth weight of progeny on mean spermatozoan head length of the sire was positive and statisti¬ cally significant. The regression of the mean mortality from birth to weaning on the mean spermatozoan head length of the sire was negative and approached statistical significance.(5) Two methods of predicting male fertility have been compared. The basis of these two methods is (a) a heterospermic insemination technique and (b) spermatozoan quality. Agreement between the two methods was extremely good.(6) Heritability estimates of six spermatozoan characteristics have been calculated