title: Non-invasive assessment of the incidences of pregnancy and pregnancy loss in the feral horses of Sable Island.
abstract: Field observations of 400 totally unmanaged feral horses on Sable Island, Nova Scotia, were complemented by oestrogen determinations in faecal samples from 154 identified females over a 4-year period (454 mare-years). Of mares that were sampled throughout the year and subsequently produced foals, 92.1% exhibited elevated faecal oestrogens between 15 October and 30 March. The results confirm that faecal oestrogens are a useful indicator of pregnancy after approximately 120 days gestation. Distribution of foaling resembled that seen in other feral populations, with 95% of births occurring from April through July. The foaling rate for mares aged 3 years or older was 62.0%, with 50.7% of mares foaling in 3 or 4 years. Foaling rates were low (4.1%) in mares bred as yearlings and rose with age to 70.8% in those bred as 4-year-olds. Fetal loss after Day 120 was deduced from faecal oestrogens to be 26.0% overall, with marked variation from year to year (9.6-37.3%) and with age (70.0% in those bred as yearlings, decreasing to 5.6% in those bred as 4-year-olds). Of 58 mares aged 2 years or older that were sampled every year, about half (49.6%) the barren years were attributable to fetal loss after 120 days gestation. All mares conceived in at least 2 of the 4 years, suggesting that pregnancy loss, even after Day 120, is as important as failure to conceive in causing barren years.
authors.affiliation: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Canada.
authors.forename: Z
authors.initials: Z
authors.lastname: Lucas
authors.forename: J I
authors.initials: JI
authors.lastname: Raeside
authors.forename: K J
authors.initials: KJ
authors.lastname: Betteridge
mesh_terms: D000034:Abortion, Veterinary / Q000453:epidemiology*; D000818:Animals; D000835:Animals, Wild / Q000502:physiology*; D001266:Atlantic Islands; D004967:Estrogens / Q000032:analysis; D005243:Feces / Q000737:chemistry; D005260:Female; D005306:Fertilization; D005865:Gestational Age; D006734:Horse Diseases / Q000453:epidemiology*; D006736:Horses; D015994:Incidence; D011247:Pregnancy; D011270:Pregnancy, Animal
chemical_list: D004967:Estrogens