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INVESTIGATIONS INTO THE ANTI-FERTILITY EFFECT OF INTRA-UTERINE DEVICES IN THE EWE

Summary.: Ovum fertilization after natural mating was inhibited in both oviducts after the insertion of a plastic spiral into one uterine horn. Spermatozoa were found in oviducts of control ewes between 4 and 24 hr after mating, but were almost totally absent from both oviducts of ewes with a spiral in one horn. Sperm numbers in the uterus were relatively low in `spiral' ewes. Spirals had these effects both 2 to 4 weeks and 8 to 10 months after insertion.

Ova were fertilized in `spiral' as well as control ewes after injection of semen into the uterus, but there were fewer accessory spermatozoa in ova from `spiral' ewes. After injection of semen into one uterine horn, spermatozoa were found throughout reproductive tracts of `spiral' and control ewes, but most spermatozoa in horns containing a spiral were broken into heads and tails. Similarly, when semen was injected into ligated uterine compartments, most spermatozoa recovered 5 hr later from spiral compartments were tailless; most spermatozoa recovered from non-spiral compartments of the same ewes were intact. Spirals inhibited sperm transport following natural mating, and they also promoted spermicidal conditions in the uterine lumen.