Distribution of β-casein variants and effects on milk composition in Podolian cows reared in Gargano Promontory (Southern Italy)

The aim of the study was to evaluate β-CN variants and their effects on milk nutritional composition and protein profile in Podolian cattle breeds reared in Gargano Promontory (Southern Italy). Individual milk samples of Podolian and Holstein Friesian (HF) cattle were analyzed for β-CN allele and genotype frequencies, chemical composition, and protein fractions of milk. In both populations, the most common allelic variant was A2, followed by A1, whereas alleles B and I had frequencies lower than 10% in both populations. A total of 6 genotypes in Podolian population (A1A2, A1B, A2B, A1I, A2I, A2A2), and 7 genotypes (A1A1, A1A2, A1B, A2B, A1I, A2I, A2A2) in HF were detected. Milk protein, lactose, and casein percentages were affected by β-CN allele in both breeds. In particular, alleles A1 and A2 resulted in higher levels of both protein and casein in HF, whereas in Podolian, allele I showed the highest, alleles A1 and A2 intermediate, and B the lowest levels of the mentioned parameters. Protein fractions were influenced by β-CN alleles, and the most abundant protein fractions were β- and α_s1-CN in both breeds, although with different percentage distribution. In Podolian milk, regardless of the detected allele, a similar behavior was observed for β- and κ-CN, and opposite to that observed for α_s2-CN. The study of the genetic variability of milk proteins offers the opportunity to valorize the nutritional, technological, and functional features of Podolian cattle dairy productions as a strategy to sustain the economic value of this ancient breed which is well adapted to the farming systems in marginal areas.