IDENTIFICATION OF A SPERM CELL ATTRIBUTE RESPONSIBLE FOR SUBFERTILITYOF ROOSTERS HOMOZYGOUS FOR THE ROSE COMB ALLELE

Fertility, sperm metabolism, sperm filling of oviductal sperm storage tubules (SST), and sperm motility were compared in subfertile roosters homozygous for the rose comb allele (R/R) and fertile controls (r/r o r R/r males). As expected, fertility of R/R males was less than that o f controls (p < 0.0001). The metabolic rate of spermatozoa from R/R ma les was also lower than that of controls (p < 0.05). Likewise, filling of SST in vivo was lower (p < 0.0001) for spermatozoa from R/R males than for control spermatozoa. However, in vitro filling of SST was not different between genotypes (p > 0.05). Motility of spermatozoa from R/R males was less than that of controls (p < 0.001) as determined by an objective spectrophotometric assay. Previous researchers have concl uded that subfertility associated with homozygosity for the rose comb allele is attributable to a sperm-specific phenomenon. However, the ce llular mechanism(s) responsible for the subfertile status were not def ined. In contrast to previous researchers, we have demonstrated that s ubfertility of R/R males is explicable in terms of reduced sperm trans port through the hen's vagina; reduced sperm motility appears to be th e major contributing factor.