Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 23, 2007
Publication Date: January 2, 2008
Citation: Silva, M.V., Van Tassell, C.P., Sonstegard, T.S., Gasbarre, L.C. 2008. Quantitative trait loci associated with parasitic infection in angus breed . Plant and Animal Genome Conference Proceedings.
In ruminants, fecal egg count (FEC) is used to measure resistance to nematodes. FEC values are not “normally” distributed and logarithmic transformations have been used for these data before analysis. However, normalization of the distribution is not achieved in most cases, especially when data are extremely skewed. The assumption of normality is very important, but there is not much information about on non-normality of data and its effect on the QTL mapping. FEC were determined for 410 animals between 1992 and 2003 from Beltsville Agricultural Research Center Angus herd. Original data were transformed using log and an extension of the Box-Cox transformation to approach normality and to estimate the position and variance components of the QTL. In total, 221 microsatellites markers were genotyped across 29 chromosomes. QTL detection was done using QxPak. Using the transformed data by Box-Cox, evidence was found for QTL on chromosome 6 for 5% chromosome-wise significant P-value. For raw and log transformation data, no QTL was found. These results indicate that after transforming data by the Box-Cox procedure the QTL mapping were more exact and has shown that some aspects of host resistance to gastrointestinal parasites are under genetic control.