Milk protein polymorphisms of Aosta Valley cattle breeds

Abstract

Cow’s milk proteins are encoded by highly polymorphic genes characterized by several mutations which result in different allelic variants. Each allelic variant has different possible effects on cheese-making properties and on human health. β-casein A1-A3-I-B, k-casein B and β-lactoglobulin B are supposed to influence milk cheese-making properties by increasing cheese or milk yield, by varying chemical parameters, by having small casein micelle size, and by influencing rennet coagulation time (RCT) and curd-firming rate (CFR). In addition, β-casein A1-B are also considered to be a risk factor for different health diseases such as ischemic heart disease (IHD), type 1 diabetes (T1D), decreased glutathione (GSH) concentration, and milk intolerance. An LC-MS method was applied to profile, for the first time, the main milk proteins genetic variants from Aosta Valley autochtonous cattle breeds. Analyses performed on milk collected from bovines of three cattle breeds (Red Pied – VRP, Black Pied – VNP and Chestnut – CAS), either from IAR experimental farm or from herds of dairy-producers in Aosta Valley region, showed quite high frequencies of β-casein A2 and A3/I, and low frequencies of β-casein A1. Moreover, low frequencies of β-casein B in VRP breed and high frequencies of the same variant in CAS, and VNP breeds have been found. As far as k-casein is concerned allelic variant B is the most diffused in VRP while allelic variant A in VNP and CAS breeds. Finally, β-lactoglobulin most diffused allelic variant for all breeds is B. Results suggest that Aosta Valley milk has good cheese-making properties and good frequencies of β-casein A2 which may be related to beneficial effects on human health. In light of these results, it is important to develop breeding programs which take into consideration milk proteins polymorphisms to further increase the milk suitability for cheese-making process and to decrease the presence of β-casein A1 and B in drinking milk which can be a risk factor for human health.