Contraceptive efficacy of an intra-uterine device in Brahman cattle

The contraceptive efficacy of an intra-uterine device was evaluated using 2 18 heifers and 212 cows on three north Australian cattle stations. The heif ers were aged approximately 2 years and weighed 250-378 kg; the cows were a ged 3-16 years and weighed 256-540 kg. All cattle were non-pregnant, non-la ctating Brahmans. At the end of the monsoon (wet) season (April-June 1997), the cattle were allocated by stratified randomisation to the three treatme nts which were untreated controls (n = 59), surgical ovariectomy (n = 105), or implantation with a bovine intra-uterine device (BIUD; n = 266). All ca ttle grazed and were managed as one group within each station. They were ex posed to bulls (4 per 100 females) from soon after treatment until slaughte r approximately 12 months later. The BIUD could not be implanted in 25% of heifers and 8% of cows due to nar row or twisted cervices. Correct placement of the BIUDs appeared to be achi eved in 57% of heifers and 72% of cows. At slaughter, the devices were inco rrectly positioned in 73% of heifers and 49% of cows into which BIUDs had b een inserted and that remained non-pregnant. Uterine perforations by the BI UD were observed in 35 and 45% of these heifers and cows. respectively; mos t perforations appeared to occur during implantation. Low-grade endometriti s was observed at slaughter in most BIUD-implanted animals; 2% had pyometra . BIUD animals did not have significantly different growth to that of control or ovariectomised animals, other than when ovariectomy suppressed growth f ollowing surgery. Most animals implanted with BIUDs appeared to have normal ovarian function and animals were observed mating. All ovariectomised anim als remained non-pregnant. Over 80% of controls were pregnant within 8 mont hs of exposure to bulls, except heifers at one station where pregnancy rate was restricted to 25% as a result of severe nutritional conditions. Pregna ncy was diagnosed in 21% of heifers and 33% of cows with implanted BIUDs. T he device remained correctly positioned and with no pregnancy diagnosed in the year following implantation in only 2% of heifers and 14% of cows origi nally allocated. Because of the difficulties of implanting BIUDs, the high frequency of asso ciated uterine injury, the high pregnancy rate in implanted animals, and th at growth was unaffected by the presence of a BIUD, it was concluded that t he device had poor contraception efficacy and no growth-promotant effect in Brahman cattle. (C) 2001 Elsevier Science B.V. All rights reserved.