A method of reducing the level of saturated fatty acids relative to the
level of unsaturated fatty acids in milk. In particular, the genotyping
and/or phenotyping of bovine cows on the basis of the amino acid residue
located at position 67 of beta-casein produced in their milk. The
invention is based on the finding that there is a correlation between the
ratio of saturated to unsaturated fatty acids in milk and the beta-casein
variants in milk.