The present invention provides a method of identifying an animal having a genotype associated with resistance to bacterial infection comprising the steps of: (a) providing a sample from said animal (b) determining the alleles at one or more markers of the SAL 1 locus to identify the genotype of the marker, wherein said SAL1 locus Lies between 54.0 MB to 54.3 MB of chicken Chromosome 5 or an equivalent thereof and (c) determining whether the genotype is a genotype associated with lance to bacterial infection.
