A multivariate snapshot of New Zealand milk seasonality in individual cows

Seasonal variation of milk composition poses a challenge for maintaining dairy product quality. Multivariate statistical techniques were used here to identify seasonal patterns in mineral levels, fatty acid profiles and selected metabolites for New Zealand raw milk collected from 24 individual cows in early-season (November), mid-season (January/February) and late-season (March). Partial least-squares discriminant analysis (PLS-DA) showed clear seasonal differences in mineral and fatty acid profiles that may have been related to supplementary feeding, dilution effects (higher total solids in late-season milk) and the lactation cycle. Fatty acid profiles showed an inverse relationship between the C6–C12 fatty acids and the branched- or long-chain fatty acids, which was thought to be related to feeding of maize in mid- and late-season. Targeted metabolite analysis suggested elevated phosphatase activity in March, and this warrants further investigation as an indicator of metabolic changes related to declining milk quality at the end of the milking season.