Contraceptive effect of plastic devices in cattle uteri.

Abstract

This study was directed toward the feasibility of installing plastic devices (IUDs) in the uteri to sterilize cattle and to obtain information regarding the mechanisms involved in any contraceptive action of such devices. Both experimental cows and controls were inseminated artificially with frozen semen from the same bull. Each cow had calved at least once previously. They were all dairy cattle in late lactation and not milked during the experimental period. Tube agglutination tests for Brucella abortus cervical mucus culture tests for Vibrio fetus and agglutination lysis tests for Leptospira pomona we re all negative. Ovarian function in each cow was ascertained by rectal palpation of the ovaries each week. Devices inserted were of polyethylene plastic of either spiral or loop shape. Large IUDs causing distension of the uterus were needed to prevent the devices from being expelled. Aseptic procedures were not used. IUDs were usually inserted during estrus and cattle were bred at successive estrous periods. After 42 services for experimental cows no evidence of conception was found in any cow. Each cow was bred again and killed after a predetermined number of days. IUDs were found in place in both uterine horns of 18 cows when they were killed after the last experimental breeding. The only possible but doubtful possibility of a subsequent pregnancy after 60 services was a 3-day cleaving ovum recovered in 1 cow. All 21 control cows were pregnant after 38 services. To determine the means by which the IUDs had acted as contraceptive agents 5 experimental cows with corpora lutea on their ovaries were killed on Days 15-19 after breeding to look for embryos in the uteri. In the case of cows this stage of gestation is over 2 weeks before implantation. No embyros were found suggesting that the contraceptive effect had occurred earlier. Normally fertilized cleaving ova can be recovered from cows oviducts in 90 percent of attempts at 3 days postbreeding. Therefore 9 cows were killed at this time and the oviducts searched for ova. A cleaving ovum was found in the oviduct of 1 cow an uncleaved ovum in the oviduct of each of 4 cows and no ova in oviducts or uteri of 4 other cows. 3 control cows with no IUDs were also killed at 3 days postbreeding. A cleaving ovum of 8 blastomeres was found in the oviduct of each of them. Results suggest that IUDs in cattle exert their contraceptive effect within the 1st 3 days postbreeding. The corpus luteum is normally detectable by rectal palpation 5-18 days postestrus. A detectable corpus luteum did not form in many estrous cycles in the experimental cows especially in those with the larger IUDs. This failure of corpus luteum would cause the death of any embryos reaching the uterus. In 4 cows large cystic follicles present on the ovaries indicated an anovulatory estrous.