Porcine β-casein: A new selection marker?

Genes encoding major milk proteins are used worldwide in marker assisted selection (MAS) in daily species: αSl-casein in goats-associated with milk protein content and flavor; K-casein and β-lactoglobulin in cattle-associated with milk quantity and quality, bovine β-casein-associated with human health, etc. Taking into consideration the fact that milk protein content varies widely within and between porcine breeds (highlighting the potential for selection) and the fact that the gene encoding the most abundant protein in sow milk, namely β-casein, is highly polymorphic, we critically reviewed the body of evidence supporting the testing of this marker for MAS. Several porcine β-casein mutations were identified, the most likely to impact milk protein content being a SNP involving an intron/exon junction (leading to alternative splicing, and the formation of new isoform) and a SNP in the gene's TATA box (leading to decreased promoter activity), with possible subsequent implications in piglet growth dynamics during the suckling period. Two relatively recent studies investigating associations between porcine β-casein polymorphisms and milk protein content were also identified. However. the methodology of the two studies and/or the polymorphisms investigated make the results difficult to interpret. In light of the recent interest toward such investigations, we conclude that porcine β-casein is a promising candidate for MAS. and that the two mutations mentioned here warrant further attention.