Authors: YAKUT ÜNVER, YAVUZ AKBAŞ, İSMAİL OĞUZ
Abstract: The purpose of the study was to investigate the effects of Box-Cox transformation on estimations of the genetic parameters for egg production traits that do not hold to the assumptions of parametric statistical analysis. Egg production of 1980 animals from 43 sires and 8 dams per sire were used. Five partial record periods were considered: 22-30 weeks of age, 31-34 weeks of age, 22-34 weeks of age, 31-40 weeks of age and 22-40 weeks of age. The egg production traits showed non-normal distributions in the form of negative skewness and positive kurtosis. The greatest departure from normality was observed in the peak period (31-34 weeks of age). After applying Box-Cox transformation, the distribution of the transformed data became closer to normality. Applying Box-Cox transformation to partial egg production data resulted in an increase in heritabilities and slightly changed genetic and phenotypic correlations. Transformation such as Box-Cox should be preferred for estimating genetic parameters from the data, when the assumptions are not satisfied.
Keywords: Box-Cox transformation, egg production, heritability, correlations
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