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Author  |
Lucas, Z.; Raeside, J.I.; Betteridge, K.J. |
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Title |
Non-invasive assessment of the incidences of pregnancy and pregnancy loss in the feral horses of Sable Island |
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Journal Article |
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Year |
1991 |
Publication |
Journal of Reproduction and Fertility. Supplement |
Abbreviated Journal |
J Reprod Fertil Suppl |
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Volume |
44 |
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Pages |
479-488 |
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Keywords |
Abortion, Veterinary/*epidemiology; Animals; Animals, Wild/*physiology; Atlantic Islands; Estrogens/analysis; Feces/chemistry; Female; Fertilization; Gestational Age; Horse Diseases/*epidemiology; Horses; Incidence; Pregnancy; *Pregnancy, Animal |
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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. |
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Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Canada |
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Language |
English |
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ISSN |
0449-3087 |
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Notes |
PMID:1795292 |
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Call Number |
Equine Behaviour @ team @ |
Serial |
2247 |
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