title: Validation of markers with non-additive effects on milk yield and fertility in Holstein and Jersey cows.
abstract: BACKGROUND
  It has been suggested that traits with low heritability, such as fertility, may have proportionately more genetic variation arising from non-additive effects than traits with higher heritability, such as milk yield. Here, we performed a large genome scan with 408,255 single nucleotide polymorphism (SNP) markers to identify chromosomal regions associated with additive, dominance and epistatic (pairwise additive × additive) variability in milk yield and a measure of fertility, calving interval, using records from a population of 7,055 Holstein cows. The results were subsequently validated in an independent set of 3,795 Jerseys.
  
  
  RESULTS
  We identified genomic regions with validated additive effects on milk yield on Bos taurus autosomes (BTA) 5, 14 and 20, whereas SNPs with suggestive additive effects on fertility were observed on BTA 5, 9, 11, 18, 22, 27, 29 and the X chromosome. We also confirmed genome regions with suggestive dominance effects for milk yield (BTA 2, 3, 5, 26 and 27) and for fertility (BTA 1, 2, 3, 7, 23, 25 and 28). A number of significant epistatic effects for milk yield on BTA 14 were found across breeds. However on close inspection, these were likely to be associated with the mutation in the diacylglycerol O-acyltransferase 1 (DGAT1) gene, given that the associations were no longer significant when the additive effect of the DGAT1 mutation was included in the epistatic model.
  
  
  CONCLUSIONS
  In general, we observed a low statistical power (high false discovery rates and small number of significant SNPs) for non-additive genetic effects compared with additive effects for both traits which could be an artefact of higher dependence on linkage disequilibrium between markers and causative mutations or smaller size of non-additive effects relative to additive effects. The results of our study suggest that individual non-additive effects make a small contribution to the genetic variation of milk yield and fertility. Although we found no individual mutation with large dominance effect for both traits under investigation, a contribution to genetic variance is still possible from a large number of small dominance effects, so methods that simultaneously incorporate genotypes across all loci are suggested to test the variance explained by dominance gene actions.
authors.affiliation: Biosciences Research Division, Department of Economic Development, Jobs, Transport and Resources, AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. hassan.aliloo@ecodev.vic.gov.au.|School of Applied Systems Biology, La Trobe University, Bundoora, VIC, 3083, Australia. hassan.aliloo@ecodev.vic.gov.au.|Dairy Futures Cooperative Research Centre (CRC), AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. hassan.aliloo@ecodev.vic.gov.au.
authors.forename: Hassan
authors.initials: H
authors.lastname: Aliloo
authors.affiliation: Biosciences Research Division, Department of Economic Development, Jobs, Transport and Resources, AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. jennie.pryce@ecodev.vic.gov.au.|School of Applied Systems Biology, La Trobe University, Bundoora, VIC, 3083, Australia. jennie.pryce@ecodev.vic.gov.au.|Dairy Futures Cooperative Research Centre (CRC), AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. jennie.pryce@ecodev.vic.gov.au.
authors.forename: Jennie E
authors.initials: JE
authors.lastname: Pryce
authors.affiliation: Biosciences Research Division, Department of Economic Development, Jobs, Transport and Resources, AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. gonzalez.oscar@inia.es.|Dairy Futures Cooperative Research Centre (CRC), AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. gonzalez.oscar@inia.es.
authors.forename: Oscar
authors.initials: O
authors.lastname: González-Recio
authors.affiliation: Biosciences Research Division, Department of Economic Development, Jobs, Transport and Resources, AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. ben.cocks@ecodev.vic.gov.au.|School of Applied Systems Biology, La Trobe University, Bundoora, VIC, 3083, Australia. ben.cocks@ecodev.vic.gov.au.|Dairy Futures Cooperative Research Centre (CRC), AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. ben.cocks@ecodev.vic.gov.au.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Cocks
authors.affiliation: Biosciences Research Division, Department of Economic Development, Jobs, Transport and Resources, AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. ben.hayes@ecodev.vic.gov.au.|School of Applied Systems Biology, La Trobe University, Bundoora, VIC, 3083, Australia. ben.hayes@ecodev.vic.gov.au.|Dairy Futures Cooperative Research Centre (CRC), AgriBio, 5 Ring Road, Bundoora, VIC, 3083, Australia. ben.hayes@ecodev.vic.gov.au.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Hayes
mesh_terms: D000818:Animals; D002417:Cattle; D002874:Chromosome Mapping; D004843:Epistasis, Genetic; D005298:Fertility / Q000235:genetics*; D005799:Genes, Dominant; D056726:Genetic Association Studies; D005819:Genetic Markers; D055106:Genome-Wide Association Study; D008892:Milk; D008957:Models, Genetic; D020641:Polymorphism, Single Nucleotide; D015203:Reproducibility of Results
chemical_list: D005819:Genetic Markers