VARIATIONS IN THE MILK-YIELD AND MILK-COMPOSITION OF DAIRY-COWS DURING LACTATION

Variations in the milk yield and milk composition of a dairy cow colon y (n = 23) were analyzed during 11 months of lactation. Milk yield fol lowed a characteristic decreasing pattern in negative correlations wit h solid components (milk protein, lactose, total solids, milk fat). Ti trable acidity (degrees SH) was significantly (P < 0.1) higher in the milk of fresh-milking cows and it correlated negatively with lactose a nd positively with milk protein, milk fat and total solids. The concen trations of Zn, Fe and Cu tended to decrease, while Mn showed insignif icant variation during lactation. Milk vitamin A showed a significant positive whilst milk vitamin E had a negative correlation with milk fa t.