SPERMATOZOA RETENTION BY SERTOLI CELLS DURING THE DECLINE IN FERTILITY IN AGING ROOSTERS

Fertility of domestic roosters peaked and then began a steep decline w ithin the first year of life. The decline was concomitant with a stead y reduction in total number of spermatozoa per ejaculate. We found tha t 1) the decline was neither related to germinal epithelium regression nor to spermatozoa abnormalities, as reported for aging males of nons easonal breeders and for fertile seasonal breeders during the nonmatin g period and 2) seminiferous tubules of extremely low-fertility aging roosters contained more Sertoli cell-spermatozoa complexes than did mo re fertile roosters, which is in sharp contrast to what occurs in othe r domestic males. We further observed that Sertoli cells of low-fertil ity roosters had smaller diameters, cytoplasm that stained deeper, and more crowded cytoplasmic inclusions than did Sertoli cells of high-fe rtility roosters. We conclude that the decline of fertility in aging r oosters is related to changes in Sertoli cells that impair the regular release of spermatozoa. Spermatozoa remain within the testicular tubu les and thus fewer spermatozoa are available for insemination.