Assessment of inbreeding depression for body measurements in Spanish Purebred (Andalusian) horses M.D. Gómez a, ⁎, M. Valera b , A. Molina a , J.P. Gutiérrez c , F. Goyache d a Department of Genetics, University of Córdoba, Ctra. Madrid-Cádiz, km 396a, 14071 Córdoba, Spain b Department of Agro-Forestal Sciences, EUITA, University of Sevilla, Ctra. Utrera km 1, 41013 Seville, Spain c Department of Animal Production, Faculty of Veterinary, UCM, Avda. Puerta del Hierro s/n, 28040 Madrid, Spain d SERIDA-Somió, C/Camino de los Claveles 604, E-33203 Gijón, Spain article info abstract Article history: Received 30 January 2008 Received in revised form 9 June 2008 Accepted 7 August 2008 Available online xxxx Our aim was to ascertain inbreeding depression in the Spanish Purebred horses for eight body measurements. A total of 16,472 individuals were measured for height at withers, height at chest, leg length, body length, width of chest, heart girth circumference, knee perimeter and cannon bone circumference. Three different multivariate animal models including, respectively, no measure of inbreeding, individual inbreeding coefficients (F i ) or individual increase in inbreeding coefficients (ΔF i ) as linear covariates were used. Significant inbreeding depression was assessed. Even though the models including measures of inbreeding fitted better with data, no effect on estimates of genetic parameters was assessed. However, the inclusion of inbreeding measures affected the ranking order according to the Expected Breeding Values (EBV). Due to the better fit with data and nice properties (the adjustment of individual inbreeding coefficients with the pedigree depth and linear behaviour) the use of ΔF i in the evaluation models can be recommended for morphological traits in horses. © 2008 Elsevier B.V. All rights reserved. Keywords: Inbreeding depression Body measurement Andalusian horse 1. Introduction The inbreeding coefficient (F) of an animal is the average probability that two genes at any given locus are identical by descent (Falconer and MacKay, 1996), and results from mating individuals related by common ancestors. Historically, inbreeding has been used in livestock breeding to “purify” the breed, to “concentrate” the good genes, and to increase uniformity of the offspring. Moreover, breeding practices that make selection programs effective in generating genetic gain also contribute to increase F and to reduce mean phenotypic values for some traits. This fact, the so called inbreeding depression, results both from the expression of partially recessive deleterious alleles and from the loss of heterozy- gosity (Charlesworth and Charlesworth, 1987; Lynch, 1991; Hansson and Westerberg, 2002; Norberg and Sorensen, 2007). Inbreeding depression is more likely to occur for traits related to reproduction and fitness (Hansson and Westerberg, 2002) whilst production or morphological traits, such as body measurements, typically show little or no change (Fioretti et al., 2002; Sierszchulski et al., 2005; Van Eldik et al., 2006; Van Wyk et al., 2006). This topic is of particular interest for populations under selection for morphological traits. How- ever, the number of studies testing this on real populations of domestic animals is scarce (Curik et al., 2003). The Spanish Purebred (SPB; Andalusian) horse is the most recognised horse breed in the Iberian Peninsula (Valera et al., 2005). At present, the SPB Stud-Book includes 66% of the registered Spanish horse population. In 2003, the Breeders' Associations of the SPB horse have initiated the development of a breeding program including conformational (Molina et al., 1999), functional (Castejón et al., 1994; Molina et al., 2007; Valera et al., 2006b, 2007) and reproduction traits (Valera et al., 2006a). Moreover, genealogical analyses have shown that a limited number of founders of the breed besides selection for type traits have caused significant inbreeding levels in this population (Valera et al., 2005). No clear evidence on detrimental effects of inbreeding on horse performance is available both at the reproduction (Dusék, Livestock Science xxx (2008) xxx–xxx ⁎ Corresponding author. Tel.: +34 957 21 87 35; fax: +34 957 21 87 07. E-mail address: pottokamdg@gmail.com (M.D. Gómez). LIVSCI-00795; No of Pages 7 1871-1413/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2008.08.007 Contents lists available at ScienceDirect Livestock Science journal homepage: www.elsevier.com/locate/livsci ARTICLE IN PRESS Please cite this article as: Gómez, M.D., et al., Assessment of inbreeding depression for body measurements in Spanish Purebred (Andalusian) horses, Livest. Sci. (2008), doi:10.1016/j.livsci.2008.08.007