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Box-Cox Transformation and Random Regression Models for Fecal egg Count Data
Marcos Vinícius Gualberto Barbosa da Silva1, Curtis P Van Tassell, Tad S Sonstegard
1Bioinformatics and Animal Genomics Laboratory, Embrapa Dairy Cattle, Juiz de Fora Minas Gerais, Brazil.
Frontiers in Genetics
|February 4, 2012
Summary
Accurate genetic evaluation of livestock requires appropriate modeling of fecal egg count (FEC) data. Random regression models and Box-Cox transformations effectively analyze skewed FEC measurements, improving heritability estimates in Angus cattle.
Area of Science:
- Animal Genetics
- Quantitative Genetics
- Parasitology
Background:
- Accurate genetic evaluation in livestock relies on precise phenotypic measurements.
- Fecal egg count (FEC) is a key indicator of nematode resistance in ruminants.
- Standard logarithmic transformations often fail to normalize highly skewed FEC data.
Purpose of the Study:
- To improve genetic evaluation models for nematode resistance in livestock.
- To assess the effectiveness of Box-Cox transformations for FEC data normalization.
- To apply random regression models (RRM) for analyzing repeated FEC measurements.
Main Methods:
- Utilized 6375 FEC measurements from 410 Angus cattle (1992-2003).
- Applied an extended Box-Cox transformation to normalize FEC data.
- Employed random regression models (RRM) with Legendre polynomials (order 4) and restricted maximum likelihood (REML) for analysis.
Main Results:
- Box-Cox transformation effectively reduced skewness and kurtosis in FEC data.
- RRM with higher-order Legendre polynomials provided the best data fit.
- Heritability estimates for FEC were significantly increased post-transformation.
- FEC measurements between 12 and 26 weeks showed significant genetic correlations.
Conclusions:
- Box-Cox transformation and RRM are effective tools for analyzing non-normally distributed FEC data.
- Improved FEC data analysis enhances genetic parameter estimation for nematode resistance.
- Genetic correlations in FEC suggest potential for selection against nematodes in Angus cattle.
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