Research Article

EFFECT OF SOME ENVIRONMENTAL FACTORS ON THE RELATIONSHIP BETWEEN CYTOLOGICAL QUALITY OF MILK AND MILK YIELD AND COMPOSITION

Anna Sawa, Mariusz Bogucki, Wojciech Neja

University of Technology and Life Sciences in Bydgoszcz

1. Acta Sci. Pol. Zootechnica, 6(2), 2007, 49‒56

Abstract. Cows from the active population of the Pomerania and Kujawy regions, calved in 1998–2002, were investigated. Statistical analyses were performed using information on milk yield, fat, protein and lactose content, and somatic cell count in the milk obtained from 846 343 test-day milkings. Correlations between LNSCC and milk traits were calculated within lactation number, stage of lactation, daily yield, season of the year, and herd size. Somatic cell count was found to have a highly significant effect on milk traits. This effect was negative for daily yield and lactose content, and positive for fat and protein content. Factors that have the strongest differentiating effect on the relationship between LNSCC and daily milk yield were the age of cows and lactation period. A stronger relationship was found between LNSCC and milk yield in older cows (>4 lactations) and in cows in the final period of lactation (>10 months). Season of the year had a weak differentiating effect on the relationship between LNSCC and daily yield and had a stronger effect on the relationships between LNSCC and fat and protein content. For LNSCC and fat content, the highest correlations were obtained in the autumn and winter months. For LNSCC and protein content, the correlations were highest in the spring and summer period.

Keywords: cows, milk, somatic cells