Seasonal variations in raw milk quality and milk production on small-holder dairy farms in Croatia

222 milk samples of Simmental cows were analysed for milk protein, milk fat, urea, lactose, SNF and SCC. The milk samples were taken in four control periods (winter-P1, spring-P2, summer-P3 and autumn-P4) and grouped according to the cows' stage of lactation (early, mid and late lactation). Very high SCC (> 1000 x 103/mL) and lower lactose content than average in 18.5% of samples were detected. The SNF content differed significantly only in period P4, with significantly lower values in the mid-lactation group. The milk urea concentration was significantly lower in period P3. The milk production and protein and energy supply in the diet were also determined. The milk production varied between control periods, with the highest in the winter and early spring, and the lowest in the summer. The fat/protein quotient in the milk was significantly higher in the early lactation group in period P2. An energy and protein surplus was detected in the late lactation group in periods P1 and P4. A protein shortage was detected in all lactation groups in period P2. Small-holder dairy farmers could have produced milk of higher and uniform quality by adequate animal feeding during the year and by reduction of the SCC in milk.