Relationships of αs1-casein (CSN1S1) and β-casein (CSN2) genotypes and their association with milk quality and coagulation properties in Bulgarian Brown cattle

Abstract

The aim of the present investigation was to establish the relationships of αs1-casein (CSN1S1) and β-casein (CSN2) genotypes in Bulgarian Brown cattle and to evaluate their association with milk quality and milk coagulation properties. Milk proteins’ polymorphism was found out in 155 tissue samples from cows reared at 4 farms. Innovative protocols and techniques were used for determination of genetic polymorphism of αs1-casein (CSN1S1) and β-casein (CSN2) in Brown cattle. After collection, tissue samples were shipped to the University in Padova, Italy for PCR-RFLP analysis. The analysis of milk composition was done in the lab of the Agriculture Institute – Stara Zagora on Lactoscan ultrasound milk analyzer, whereas coagulation properties of individual milk samples were evaluated on a Computerized Renneting Metter – Polo Trade, Italy. During the study, the following parameters were studied: milk fat and protein contents (%), rennet coagulation time (RCT, min), curd firmness (а30, mm) and curd firming time (k20, min). Heterozygous cows for both studied milk proteins: CSN1S1 and CSN2, had higher milk fat and milk protein percentages, 4.71% fat and 3.45% protein in genotype ВС of CSN1S1 and 5.00% fat and 5.33% protein in genotype АВ of CSN2. The milk of cows from different CSN1S1 and CSN2 genotypes was outlined with moderate curd firmness and good coagulation time. Homozygous cows for both studied milk proteins had higher curd firmness (32.31 mm) for the ВВ genotype of CSN1S1 and 31.29 mm for the АА genotype of CSN2.