Relationship between Lactoferrin and Beta-Lactoglobulin Genes with the Milk Quality Traits and Somatic Cell Counts in Crossbred Dairy Cattle Genotypes

The beta-lactoglobulin (BLG) gene is an acid-stable, amphiphilic, and a single chain polypeptide of 18kbp. It occurs in three different forms: Tetrameric, octameric, and multimeric (Al Shabib et al., 2020). The gene comprises 10-15% and 53 % of milk and whey protein respectively (Alim et al., 2015). It is a whey protein commonly present in milk at normal pH (Alim et al., 2015; Singh & Gallier, 2018). Beta-lacto globulin is one of the whey proteins and lipocalin present in cow milk. The lipocalin protein adheres easily to several hydrophobic molecules. The Beta-lactoglobulin gene can bind iron through siderophores, thus playing a critical role infighting pathogens in milk. Therefore, it is a candidate gene associated with somatic cell count and milk quality trait in bovines (Alim et al., 2015; Singh et al., 2015).

Beta-lactoglobulin gene inhibits the growth of common causative agents of mastitis such as Staphylococcus aureus and Streptococcus spp. The action reduces the spreading rate of infections, which helps improve the quality of milk (Chaneton et al., 2010; Ateya et al., 2016). Due to its ability to influence the number of somatic cells in milk, the lactoferrin gene is an appropriate novel candidate gene for selecting mastitis resistance in dairy herds (Martin et al., 2018). The bovine lactoferrin gene belongs to the transferrin family (Firyal et al., 2017). The gene is a glycoprotein found inmost biological fluids such as saliva, bile, blood, milk mucous secretions, and tears (Chopra et al., 2013; Asadollahpour et al., 2016). In bovines, the concentration varies between 0.02 and 17.8 mg/ml. The concentration can rise sharply with udder infection (Zabolewicz et al., 2012; Sharma et al., 2015). The genomic DNA of this gene has a molecular size of 34.5kb (Dinesh et al., 2015). The gene is secreted in milk during lactation by polymorph nuclear Neutrophils (Nanaei et al., 2016). In bovine milk, the lactoferrin gene plays biological and physiological roles and is strongly correlated to Somatic Cell Count (Cheng et al., 2008; Arnould et al., 2009; Pawlik et al., 2014). The concentration of protein in milk is determined by a number of many factors, including parturition, lactation stage, days of involution, subclinical and clinical mastitis (Sharma et al., 2015). The high concentrations of the lactoferrin gene in milk can be an indicator of milk quality and subclinical mastitis (Musayeva et al., 2018). High concentrations are usually recorded in cows undergoing drying-off cows and mammary involution (Zabolewicz et al., 2014).

The increased SCC results in a decline in the amount of the beta-lactoglobulin gene in milk (Litwi et al., 2011). The gene works in an antagonistic manner to the lactoferrin gene, but both possess antibacterial effects. Therefore, the two genes can complement the mammary gland immune mechanisms against bacterial infections (Chaneton et al., 2010; Singh et al., 2014). SCCs monitor the general udder health, including subclinical mastitis in dairy cows (Singh et al., 2014). Early detection by the farmer is essential because it can help them maximize their profits by reducing the cost of milk production and disease control. Therefore, this study offers important insight into evaluation of the relationship between genes associated with milk quality and Somatic Cell Counts in crossbred dairy cattle.