Physicochemical properties of milk fat from three breeds of cows during summer and winter feeding

Abstract. The investigations included total 515 milk samples which were collected from 309 cows of the main dairy cows’ breeds used in Poland, i.e. Polish Holstein-Friesian Black-White variety (n=150), Polish Holstein-Friesian Red-White variety (n=77) and Simmental (n=82). There was determined a content of fat, protein and dry matter, a share of fat globules ranging in size, i.e. <6 μm, 6-10 μm and >10 μm as well as a fatty acids profile. It was shown that milk gained from Holstein-Friesian cows was characterized with a higher level of fat dispersion (over 70 % globules of <6 μm diameter and a higher percentage of short- and long-chain fatty acids (ca. 19 %). The Simmentalers’ milk had a higher protein : fat ratio (about 0.89), a lower fat dispersion level (8.21 % globules of >10 μm diameter) and the highest share of the polyunsaturated fatty acids (3.28 %). Cows nutrition included pasture forage during summer (independently on the breed) had a significant influence (P≤0.01) on increased polyunsaturated fatty acids percentage (mean by 0.51 %). The winter milk, however, showed a significantly higher content of dry matter, fat and protein as well as a higher share of big-sized milk globules.