2009-Schurink_et_al - Heritability and repeatability of...

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A. Schurink, E. M. van Grevenhof, B. J. Ducro and J. A. M. van Arendonk breeding mares Heritability and repeatability of insect bite hypersensitivity in Dutch Shetland doi: 10.2527/jas.2008-1129 originally published online Sep 12, 2008; 2009.87:484-490. J Anim Sci http://jas.fass.org/cgi/content/full/87/2/484 the World Wide Web at: The online version of this article, along with updated information and services, is located on www.asas.org by on February 2, 2011. jas.fass.org Downloaded from
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ABSTRACT: Insect bite hypersensitivity (IBH) is a seasonal recurrent allergic reaction of horses to the bites of certain Culicoides spp. and is found through- out the world. The aim of our study was to estimate the heritability and repeatability of IBH in the Dutch Shetland pony population. A total of 7,924 IBH scores on 6,073 mares were collected during foal inspections in 2003, 2005, and 2006. Mares were scored for clinical symptoms of IBH from June until February by 16 in- spectors. Of all mares, 74.4% (n = 4,520) had a single observation, 20.7% (n = 1,255) had 2 observations, and 4.9% (n = 298) had 3 observations in different years. The overall mean IBH prevalence was 8.8%. Heritability was 0.08 (SE = 0.02) on the observed binary scale and 0.24 (SE = 0.06) on the underlying continuous scale. Repeatability was 0.30 (SE = 0.02) and indicates that including repeated observations of the clinical symp- toms of IBH will improve the accuracy of breeding val- ues for IBH. We conclude that IBH, based on clinical symptoms, is a heritable trait in the Dutch Shetland pony population. Therefore, the IBH prevalence in this population can be decreased by selection. Key words: heritability, horse, insect bite hypersensitivity, repeatability ©2009 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2009. 87:484–490 doi:10.2527/jas.2008-1129 INTRODUCTION Insect bite hypersensitivity ( IBH ) is a seasonal re- current allergic reaction of horses to the bites of cer- tain Culicoides spp. (Riek, 1954). The allergic reaction causes intense pruritus, which results in self-inflicted trauma; open wounds and secondary infections may follow. Therefore, the welfare of affected horses is seri- ously reduced. The commercial value of affected horses is also reduced because of disfiguration (Broström et al., 1987; Fadok and Greiner, 1990). Due to extreme discomfort, affected horses are often unsuitable for rid- ing or showing purposes (Gortel, 1998). There is no currently available effective treatment for or prevention against IBH (Anderson et al., 1996; Friberg and Logas, 1999; Pilsworth and Knottenbelt, 2004). The etiology of IBH is multifactorial in origin and in- volves environmental and genetic factors (Lange, 2004; Björnsdóttir et al., 2006; Grandinson et al., 2006). Although warm- and cold-blooded horses of various breeds worldwide are affected (Anderson et al., 1988; Littlewood, 1998; Steinman et al., 2003), heritabilities of IBH have been estimated only in small populations of Icelandic horses (Unkel et al., 1987; Lange, 2004; Grandinson et al., 2006). Therefore, no heritability es- timates in breeds other than Icelandic horses are avail- able in the scientific literature.
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2009-Schurink_et_al - Heritability and repeatability of...

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