A field study of patterns of unobserved foetal loss as determined by rectal palpation in foaling, barren and maiden thoroughbred mares.
Records of 1,009 pregnancies in 574 foaling, barren and maiden Thoroughbred mares on a single stud farm, over a period of 12 years were examined. The farm is situated in the eastern Cape Province of South Africa, at an elevation of 1,800 m, and in an area of climatic extremes. Records of 604 pregnancies in 249 foaling Thoroughbred mares were examined. For these purposes, those pregnancies in which a mare conceived in the same breeding season during which she had foaled were considered as pregnancies in foaling mares. Pregnancy was confirmed by rectal palpation by a single experienced practitioner. Of the 604 pregnancies examined, conceptus attachment occurred in the horn opposite the previously gravid horn in 345 cases (57%), and in the previously gravid horn in 259 cases (43%; P less than 0.005). Unobserved foetal loss after pregnancy diagnosis amounted to 30 (9%) in the former group, while in the latter group (pregnancy established in the postgravid horn) 46 pregnancies were lost (18%; P less than 0.005). This study confirmed that conceptus attachment tends to occur in the uterine horn opposite the previously gravid horn in foaling Thoroughbred mares conceiving during the same season. A significantly higher incidence of foetal loss accompanied conceptus attachment in the postgravid horn. Of 242 pregnancies in 162 previously barren mares, 95 (39%) occurred in the left uterine horn and 147 (61%) in the right horn (P less than 0.005). The incidence of pregnancy failure in this group was 7%. The side of attachment did not affect the rate of loss. Evaluation of the records of 163 maiden mares revealed that conceptus attachment occurred in the left uterine horn in 58 (36%) pregnancies and in the right horn in 105 (64%) pregnancies (P less than 0.005), which is consistent with previously reported observations. Pregnancy failure was recorded in 4% of maiden mares. Side of attachment did not influence rate of loss in this group.
Gilbert
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Department of Clinical Sciences, NYS College of Veterinary Medicine, Cornell University, Ithaca 14853-6401.
Marlow
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D000818:Animals; D005260:Female; D005313:Fetal Death / Q000453:epidemiology / Q000662:veterinary*; D006734:Horse Diseases / Q000453:epidemiology*; D006736:Horses; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000662:veterinary*; D011258:Pregnancy Tests / Q000662:veterinary; D011270:Pregnancy, Animal / Q000502:physiology*; D012189:Retrospective Studies; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology