Theory of ammonia toxicity as the mechanism of abortion in the mare reproductive loss syndrome |
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| Authors: | Jennifer R. Taylor |
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| Affiliation: | 1. Alunos do Programa de Pós-Graduação de Medicina Veterinária (PPGMV), Universidade Federal de Campina Grande (UFCG), Patos, PB, Brazil;2. Instituto Federal de Educação, Ciência e Tecnologia da Paraíba (IFPB), Faculdade de Medicina Veterinária, Sousa, PB, Brazil;3. Aluna do Programa de Pós-Graduação em Ciência Animal (PPGCA), Universidade Federal de Campina Grande (UFCG), Patos, PB, Brazil;4. Docentes Programa de Pós-Graduação de Medicina Veterinária (PPGMV), Universidade Federal de Campina Grande (UFCG), Patos, PB, Brazil;1. Animal Welfare Science Centre, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Australia;2. Rivalea Australia, Corowa, Australia;1. Clinic of Animal Reproduction, Faculty of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany;2. Tierärztliche Praxis Am Weinberg, Jessen, Germany;1. DELTA Group, University of California, Davis, CA 95616, USA;2. University of Houston, Houston, TX, USA;3. US Environmental Protection Agency, National Exposure Research Laboratory, Research Triangle Park, NC 27711, USA;4. US Environmental Protection Agency, National Risk Management Research Laboratory, Research Triangle Park, NC 27711, USA |
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| Abstract: | In late April/early May of 2001, for the equine industry in Kentucky, a previously unknown factor led to the loss of up to 40% of the new pregnancies (20-60 days) for that year, with a following significant number of late abortions and ill new born foals. In addition, encephalopathy, ocular lesions, pericarditis, laminitis, and other diseases were suspected to be associated with the syndrome. This occurrence was known as the mare reproductive loss syndrome (MRLS). On examination of the weather data, this period was seen to have an unusual pattern of severe late spring frost. Acute changes in the pasture diet affected the horses gut microflora, allowing the overgrowth of opportunistic pathogens and resulting in the excessive absorption of nitrogen and ammonia from the large bowel. Clinical blood chemistries from the horses on pasture at this time showed abnormally high levels of blood urea nitrogen (BUN). Elevated blood ammonia levels were found in mares and newborn foals affected with MRLS. Ammonia is metabolically one of the most toxic substances to the body. It is present naturally as a breakdown product of nitrogen turnover. If the body nitrogen balance is disturbed for any reason, with nitrogen accumulation exceeding the body's ability to excrete it as urea (BUN), ammonia will accumulate in toxic levels. Ammonia toxicity can cause all the symptoms that were observed in the horses exhibiting MRLS. |
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