Epistatic genetic variances for litter size in pigs using genomic models Z.G. Vitezica1, H. Crichan1, W. Herring2, A. Reverter3 & A. Legarra1 1 INRA/INPT, UMR 1388 GenPhySE, F-31326 Castanet-Tolosan, France zulma.vitezica@ensat.fr (Corresponding Author) 2 PIC North America, Hendersonville, USA 3CSIRO Agriculture & Food, 306 carmody Rd., St Lucia, Queensland 4067, Australia Epistatic genomic relationship matrices for interactions of any-order can be constructed using Hadamard products of additive and dominant genomic orthogonal matrices plus a standardization based on the trace of these matrices. With a pig genomics dataset, the broad-sense heritability for litter size was almost twice the narrow-sense heritability. Estimates of variance components were stable across models. Including epistasis reduced bias without changing prediction accuracy in the genetic evaluation. Epistasis can be exploited in mating allocation to maximize the overall genetic merit.