2009-Casellas_et_al - Analysis of founder-specific...

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J. Casellas, J. Piedrafita, G. Caja and L. Varona Analysis of founder-specific inbreeding depression on birth weight in Ripollesa lambs doi: 10.2527/jas.2008-0897 originally published online Sep 12, 2008; 2009.87:72-79. J Anim Sci http://jas.fass.org/cgi/content/full/87/1/72 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 October 22, 2010. jas.fass.org Downloaded from
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ABSTRACT: Although inbreeding ( F ) is a topic of major concern in animal breeding, estimates of inbreed- ing depression are usually obtained by modeling the overall F coefficient of each individual, without consid- ering that the recessive (deleterious) genetic load of a given population may be unevenly distributed among the founder genomes. The founder-specific partial F co- efficient is calculated as the identity-by-descent prob- ability at any given autosomal locus related to a par- ticular founder and allows a more detailed analysis of inbreeding depression on productive traits. Within this context, birth BW data from 2,459 Ripollesa lambs were analyzed under a hierarchical animal model without F - related covariates (model 0), with inbreeding depres- sion modeled by the overall F coefficient (model F1), or by the partial F coefficient of 9 founders that made a relevant contribution to the population inbreeding (model F2). A straightforward empirical Bayes factor (BF) was developed for testing statistical relevance of each F -related covariate, in which greater-than-1 values favored the model including the covariate. The deviance information criterion (DIC) clearly supported model F1 (5,767.8) rather than model 0 (5,771.2), suggesting that inbreeding depression had a relevant influence on birth BW data. The linear effect of inbreeding depression was statistically relevant in model F1 (BF = 2.52 × 10 35 ), with lamb birth BW declining by −13.6 g with each 1% F increase. The quadratic effect of inbreeding depression was almost null in model F1 (BF = 0.02), as suggested by the reduction in DIC (5,766.9) when this effect was removed from model F1. On the other hand, model F2 provided a similar DIC (5,767.9) value, with this parameter decreasing to 5,764.7 when nonrelevant founder-specific inbreeding depression effects were re- moved. Substantial heterogeneity in founder-specific inbreeding depression was reported by model F2, in which estimates for 4 of the 9 founders did not differ from zero (BF between 0.05 and 0.42), whereas 5 found- ers originated moderate (−8.2 g for each 1% F increase; BF = 1.42) to large inbreeding depression (−96.2 g for each 1% F increase; BF = 8.80 × 10 19 ). The substan- tial variability between founder estimates suggested that inbreeding depression effects may mainly be due to a few alleles with major deleterious effects. These re- sults contribute valuable information that should help to achieve more accurate management of inbreeding in the Ripollesa breed.
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This note was uploaded on 01/26/2012 for the course ECON 2272 taught by Professor Gay during the Spring '08 term at Birmingham-Southern College.

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2009-Casellas_et_al - Analysis of founder-specific...

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