To Box-Cox or not to Box-Cox: phenotypic and genomic evaluation of litter size variability in Landrace pigs

This study aims to evaluate phenotypic and genomic background of variability of litter size obtained from data without and with Box-Cox transformation. We used 67,500 records on total number born (TNB) from Landrace pig population. Since the original data presented skewness the decision was made to perform Box-Cox transformation (bcTNB). Phenotypic variability was estimated as log-transformed variance of residuals (LnVar) for both TNB and bcTNB. EBVs obtained with LnVar were used to calculate the deregressed EBV, which were further used in genome-wide association study (GWAS) on ~5,000 sows and boars genotyped or imputed to 660K SNP-chip. The final GWAS results are still to be developed.