Variation of detailed protein composition of cow milk predicted from a large database of mid-infrared spectra

Abstract

This study aimed to investigate factors aecting protein fractions, namely α-casein (α-CN), β-casein (β-CN), ĸ-casein (ĸ-CN), β-lactoglobulin (β-LG) and α-lactalbumin (α-LA) predicted frommilk infrared spectra in milk of dairy and dual-purpose cattle breeds. The dataset comprised 735,328 observations from 49,049 cows in 1782 herds. Results highlighted significant dierences of protein fractions in milk of the studied breeds. Significant variations of protein fractions were found also through parities and lactation, with the latter thoroughly influencing protein fractions percentage. Interesting correlations (r) were estimated between β-CN, ĸ-CN and β-LG, expressed as percentage of crude protein, and milk urea nitrogen (r = 0.31, 0.20 and 0.26, respectively) and between α-LA and fat percentage (r = 0.41). The present study paves the way for future studies on the associations between protein fractions and milk technological properties, and for the estimation of genetic parameters of predicted protein composition.