Phenotypic variation of lactoferrin content in bovine milk

Lactoferrin (LF) is an iron-binding glycoprotein found in milk and in other exocrine secretions and neutrophil granules of mammals. It is widely regarded as an effective host defense molecule. The positive charge and its wide distribution allow it to be a multifunctional molecule with anti-microbial/antiviral, immunomodulatory, and antioxidant properties. The amount of LF is lower in cows than in human milk. Several factors such as milk yield, diet, herd, stage of lactation, parity, and health condition of the animal influence the concentration of LF. The aim of this thesis was to investigate sources of variation of LF in the milk of three cattle breeds (Holstein, Simmental, and Rendena) using radial immunodiffusion assay and to assess the correlations between LF and the major milk quality traits. A total of 2,538 milk samples from 45 commercial herds located in the Veneto region (Italy) were collected between September and December 2020. Milk samples were analysed for milk chemical composition and LF concentration. Pearson correlations between milk yield, chemical composition, and LF were estimated. Sources of variation of LF concentration were investigated using a mixed linear model that included the fixed effects of breed, days in milk and parity, and the random effects of herd nested within breed and the residual. The LF showed a negative correlation with milk yield and moderately positive correlations with protein, casein, and somatic cell score. The concentration of LF was strongly influenced by parity and days in milk, whereas cow breed was not significant in explaining the variation of LF. Despite not being significant, the concentration of LF was greater in the milk of Simmental than Holstein and Rendena cows. Further investigations are required upon these results by expanding the sample size, especially for Simmental and Rendena breeds. Also, future studies will investigate genetic aspects of LF in milk to evaluate the possibility to select for this compound.