SPERM STORAGE AND TRANSPORT FOLLOWING NATURAL MATING AND ARTIFICIAL-INSEMINATION

Recent observations in turkey and chicken hens show that sperm storage in both species is a highly inefficient process. After artificial ins emination (AI), less than 1% of spermatozoa inseminated are selected f or transport to and enter the sperm storage tubules (SST). It has been shown that the sperm selection process is orchestrated within the vag ina and not at the level of the SST. At least two mechanisms are invol ved in the selection of spermatozoa fit for sperm storage, one being m echanical (motility) and the other biochemical in nature (sperm-vagina l mucosa interactions). Furthermore, it was also observed that the spe rm storage efficiency in the chicken is dependent upon the logarithm o f the number of spermatozoa inseminated. From a practical standpoint, inseminations performed frequently with a moderate number of spermatoz oa should be more efficient than inseminations performed with higher d oses at longer intervals. Maximal filling of the SST of hens in egg pr oduction requires only 1 day for the chicken and 2 days for the turkey . By contrast, the release of sperm from the SST is about seven times faster in the chicken than the turkey hen. The efficiency of oviducal sperm storage is related to a number of factors including age of the h en, stage of the ovulatory cycle when inseminated, and, in the turkey, if the hen was inseminated before or after the onset of egg productio n. Two different categories should be considered among factors that af fect sperm survival in vivo. 1) Factors affecting sperm storage. These factors, acting in the vaginal portion of the oviduct, regulate the m igration of spermatozoa up to the SST by increasing (e.g., short inter vals between oviposition and AI) or decreasing (e.g., sperm migration in prelaying hens) the barrier effect of the vagina. 2) Factors affect ing sperm release. In chicken hens, the hen's age does not impair the sperm storage efficiency but rather increases the rate of release of s permatozoa, thus contributing to a shorter duration of fertility.