Until last decade, genetic polymorphism screenings on lactoproteins relied on direct characterisation of their primary structures, restricting the analysis spectrum to adult lactating females, as well as other limitations concerning sensitivity of detection. The fast development of DNA molecular techniques since then has made possible the identification of milk protein genotypes in both sexes at birth, considerably increasing their potential value as an aid for genetic selection. Genotyping of A.I. sires integrated in breeding programs, of growing interest due to significant differences in physico‑chemical and technological properties of milk associated with certain variants, is now feasible, circumventing the need of indirect information as deduced from ancestors, mates and daughters.
In this work, several mutation detection techniques are reviewed, from initial molecular typing protocols based on restriction enzyme digestion of genomic DNA coupled to hybridisation with specific probes ‑the Southern technique‑, to those procedures based on previous amplification of a specific genomic segment through Polymerase Chain Reaction (PCR ). Here, we focuse on methods already applied to the field of genetic polymorphism of lactoproteins in domestic ruminants: cow (Bos taurus), goat (Capra hircus) , and sheep (Ovis aries).