Abstract
The goal of this study was to determine the mechanism by which the fertility was declined by repeated artificial insemination (AI) in laying hens. The structures of sperm storage tubules (SST) and lymphocytes population in the uterovaginal junction (UVJ) of Rhode Island Red hens showing a declined fertility after repeated AI with Tosa-jidori semen and of virgin hens were examined histologically in experiment 1. Then, the sperm storage abilities of those hens were examined in experiment 2. In experiment 1, the SST was swollen with thinning of epithelium, and the population of lymphocytes was greater in the UVJ of hens showing a declined fertility after repeated AI compared with virgin hens. In hens showing a lower fertility, few sperm were present in SST, and lymphocytes invading into SST lumen after AI were observed (experiment 2). These results suggest that repeated AI may cause the destruction and abnormality in the functions of SST, and anti-sperm immunoresponse may occur in those SST in the birds used for current study. In these birds sperm could not be retained in SST, resulting in decline of fertility. Such abnormality of SST may be one of the factors involved in the decline of fertility by repeated AI in the other breeds that are reported elswhere.
