Association of cattle genetic markers with performance traits

Abstract

Milk protein polymorphism genetic variants of bovine milk proteins Alfas1-CN-casein, Kapa-CN-casein, Beta-LG-lactoglobulin and polypeptide hormone prolactin (PRL) were studied in two native cattle breeds – Lithuanian Light Grey and Lithuanian White Backed and in two modern cattle breeds – Lithuanian Black and White and Lithuanian Red – by polymerase chain reaction (PCR). The aim of this study was to investigate the distribution of cattle genetic markers and to evaluate them as potential markers of milk performance traits in Lithuanian dairy cattle breeds. Two different alleles of polypeptidic hormone PRL were detected in four Lithuanian cattle breeds. The PRL gene A allele was found with a higher frequency in Lithuanian White Backed cattle breed and it was the least frequent in Lithuanian Red cattle breed. Three genotypes were identified for polypeptidic hormone PRL (AA, AB and BB) in Lithuanian breeds. Prolactin gene AA genotype was the most frequent in all investigated breeds. A higher influence of PRL gene was evaluated for milk fat percentage (12.12%, p < 0.001). Lithuanian dairy cattle breeds were investigated for three milk protein systems and eight 8 different milk protein types. According to research results, the B types of Alphas1-casein were found as predominant in all four breeds studied. The most common A and B types of milk protein Kapa-CN were found at a high frequency in all cattle breeds. In Lithuanian Red, important B types were found at a higher frequency. The obtained results for three milk protein systems loci showed higher influence of Kapa-casein gene on milk protein percentage (5.9%, P < 0.001). All Lithuanian dairy cattle breeds showed a high frequency of whey protein Beta-lactoglobulin B types, the highest being in Lithuanian Red breed and the lowest in Lithuanian Light Grey. Keywords: prolactin, casein, lactoglobulin, milk, cattle