Milk mineral variation of Italian dairy cattle breeds predicted by mid-infrared spectroscopy

Consumer’s quality perception has changed in the last years and healthy aspects are becoming more and more relevant. Cow milk is an important source of minerals, especially Ca, K, Mg, Na, and P. Large-scale monitoring of milk mineral content is difficult due to expensive and time-consuming reference analyses, and therefore phenotyping of these traits at the population level is hardly achievable. Aim of the present study was to investigate sources of variation of milk Ca, K, Mg, Na, and P, predicted by mid-infrared spectroscopy models developed after uninformative variables elimination, on a large multi-breed spectral dataset (n=123,240). Cattle breeds considered were Holstein-Friesian, Brown Swiss, Alpine Grey, and Simmental. Sources of variation were studied using mixed models, including the fixed effects of breed, month and year of sampling, days in milk, parity, and the interactions between the main effects. Random factors were herd nested within breed, cow nested within breed, and the residual. All fixed effects were highly significant (P<0.01) in explaining the variation of milk mineral concentration. Milk of Simmental cows exhibited the greatest concentration of minerals. Alpine Grey breed had greater concentration of Ca and P compared to HF. These aspects could be important for a valorization of local breeds. Variation of concentration of Ca, Mg, Na, and P across lactation was significant and it exhibited an opposite trend to that of milk yield, with the lowest values around the peak of lactation. On the contrary, K concentration resembled the trend of milk yield.