Seasonal Influences on Milk Yield and Composition Dynamics during a Normal Lactation in Dairy Cows: Milk Yield, Fat and Protein Precentage

Researches were made on 125 lactations from Romanian Black Spotted cows and aimed to study the evolution of the interval between calving on milk yield and quality. Data were recorded and statistically analyzed by means of ANOVA / MANOVA determining the average values and dispersion indices. Based on averages parameters of lactation curves were calculated using the mathematical model called the incomplete gamma function.Cows that calved in winter and spring had steeper lactation curves for milk yield. The lactation curve for butter-fat percentage was significantly different (p<0.05) between summer-winter and summer-autumn seasons. Evolution of the lactation curve for protein percentage was significantly different (p<0.05) between winter and spring, distinct significant (p<0.01) between summer-autumn, winter-autumn and very significant (p