Lactoferrin content determined in bovine milk by HPLC and mid-infrared spectrometry - Relation to udder health and potential for detection of milk adulteration

Lactoferrin (LF) isamultifunctional glycoprotein linked toudder health indairy cows. This study aimed todevelop acalibration model for LF quantification using mid-infrared spectrometry (MIR-FT), with ion-pair reversed-phase high-performance liquid chromatography (HPLC) asthe reference method. Two sets ofindividual milk samples (A: n= 120; B: n= 91) were collected from five dairy farms inthe Czech Republic. Set Aincluded ahigher proportion ofsamples with somatic cell count (SCC) above 300 000 cells/ml toensure broad LF variability. After merging both sets and removing six outliers, afinal calibration set C (n= 205) was created. The developed model achieved across-validated coefficient ofdetermination of0.5887 and astandard error ofcross-validation of67.33 mg/l. Correlation analysis showed that several milk parameters correlated with LF determined byMIR-FT inpatterns typical ofmastitis (SCC: r=0.450; lactose: r= –0.364; free fatty acids: r= 0.621; electrical conductivity: r= 0.442), indicating potential for MIR-FT inevaluating mammary gland health. The feasibility ofusing LF asanindicator ofmilk adulteration byartificial SCC reduction through centrifugation was also assessed. Two sample sets (n= 20 and n= 68) were analysed, each containing normal bulk tank milk and bulk tank milk supplemented with abnormal milk. Centrifugation caused minimal changes inLFdetermined byboth HPLC and MIR-FT (maximum 3.27%) while SCC decreased bynearly 50%, suggesting thatLF may serve asamarker for detecting artificial SCC reduction. However, practical application ofMIR-FT for accurate LF determination islimited bythe achieved validation parameters and the high expanded uncertainty (114.7mg/l). The method istherefore more suitable for monitoring relative LF changes inmilk than for determining exact LF content.