Effect of Repeated Cabergoline Treatment on the Vernal Transition and Hair Shedding of Mares (Year 1) and a Subsequent Comparison of the Effect of Starting Date on Prolactin Suppression (Year 2) |
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| Institution: | 1. School of Veterinary Science, The University of Queensland, Gatton Campus, Gatton, Queensland, Australia;2. School of Veterinary Medicine and Animal Science, University Estadual Paulista, Botucatu, São Paulo, Brazil;1. Department of Veterinary Sciences, University of Pisa, Via Livornese, San Piero a Grado, 56124 Pisa, Italy;2. Ecole Nationale Vétérinaire, Agroalimentaire et de l’Alimentation Nantes Atlantique-ONIRIS, 102 Route de Gachet, 44300 Nantes, France;1. Division of Endocrinology and Molecular Medicine, Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA;2. Department of Veterans Affairs, Lexington, KY, USA;1. Materials Science and Technology Center, UdR INSTM, University of Perugia, str. di Pentima 4, 05100, Terni, Italy;2. Civil, Chemical, Environmental and Materials Engineering Dept. (DICAM), University of Bologna, Via Terracini 28, 40131, Bologna, Italy;3. Department of Chemistry, Biology and Biotechnology, Biochemistry and Molecular Biology Unit, University of Perugia, Via del Giochetto, 06126, Perugia, Italy |
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| Abstract: | Two studies were conducted to determine efficacy of cabergoline for suppressing prolactin (PRL) and the possible effects on vernal transition in mares. In experiment 1, six mares each received either vehicle or cabergoline (5 mg, intramuscularly) every 10 days for 12 treatments beginning February 4, 2013. Blood samples were drawn regularly, and mares were challenged with sulpiride periodically to assess PRL suppression. Weekly hair samples were obtained to determine shedding. Prolactin was suppressed (P < .05) by cabergoline, but suppression waned in spring. There was no effect (P > .05) of treatment on day of first ovulation, luteinizing hormone, or follicle stimulating hormone. Hair shedding was generally suppressed (P = .05). In 2014 (experiment 2), eight of the same 12 mares were used in a similar experiment to determine if the rise in PRL observed in experiment 1 was due to refractoriness to cabergoline or perhaps another factor. Treatment began on April 6, 2014, corresponding to the increase in PRL in treated mares in experiment 1. Mares were treated with cabergoline or vehicle until June 5. Prolactin was suppressed (P < .05) by cabergoline, and the pattern of apparent escape from suppression was similar to year 1. We conclude that (1) cabergoline at this dose alters hair shedding but does not alter the time of first ovulation in mares and (2) relative to our previous reports of cabergoline treatment in the fall, there is a seasonal effect on the ability of this dose of cabergoline to suppress unstimulated PRL secretion. |
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| Keywords: | Prolactin Cabergoline Dopamine Mare Anestrous |
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