The invention relates to methods to select animals, such as mammals, in particular, domestic animals such as breeding animals or animals destined for slaughter, for having desired genotypic or potential phenotypic properties, in particular, related to muscle mass and/or fat deposition or, in the case of mammals, to teat number. The invention provides a method for selecting an animal for having desired genotypic or potential phenotypic properties comprising testing the animal, a parent of the animal or its progeny for the presence of a nucleic acid modification affecting the activity of an evolutionary conserved CpG island, located in intron 3 of an IGF2 gene and/or for the presence of a nucleic acid modification affecting binding of a nuclear factor to an IGF2 gene.