Possible causes of subfertility in hens following insemination near the time of oviposition.

Spermatozoa incubated in uterine fluid collected 7 or 18 h after ovulation showed no significant differences either in motility or in fecundity, despite wide variations of composition of the uterine fluid itself. The absence of uterine fluid in the oviduct 1 h before oviposition may be partially responsible for spermatozoa being unable to migrate easily to the storage sites after insemination of this time. Females inseminated intravaginally at the presumed time of oviposition showed consistently low fertility, irrespective of whether an egg was present in the uterus or not. Normal fertility rates could be achieved with inseminations intravaginally at or near the time of oviposition if the uterine contractions associated with oviposition were inhibited by treatment with indomethacin. Hens inseminated intravaginally 1 h after oviposition retained lower proportions (0.4 to 0.7%) of the initial dose of spermatozoa (measured 2 h after insemination) in their oviduct that hens inseminated 5 to 6 h after oviposition (4.5 to 23.3%).