Med. Weter. 71 (4), 231-235, 2015

full text

Litwińczuk Z., Barłowska J., Król J., Brodziak A., Matwijczuk A., Kowal M.
Chemical composition and technological suitability of milk with regard to the feeding system of cows
The aim of the study was to assess the changes in daily productivity, chemical composition, i.e. cholesterol content and parameters of technological suitability of milk obtained in the intensive and traditional systems in the following stages of lactation. A total of 2,112 milk samples of which 1,143 collected from 273 cows maintained in farms with an intensive milk production technology (loose cow houses and TMR feeding system) and 969 collected from 231 cows from farms with a traditional production system (seasonal feeding with share of pasture) were evaluated. The samples were divided into three groups with regard to stage of lactation, i.e. I – up to 120 days, II – from 121 to 200 and III – above 200. Basic chemical composition (protein, fat, lactose and dry matter), content of casein, non-fat dry matter and cholesterol, protein to fat ratio, active and potential acidity, thermal stability, rennet coagulation time and dispersion state of milk fat were determined. It was shown that daily milk yield (averagely 23.38 kg) was almost twice as high (p≤0.01) in the intensive system in comparison to the conventional system (14.53 kg). Milk from cows maintained in the intensive system also contained significantly (p≤0.01 and p≤0.05) more protein (on average 3.66 %), fat (4.45 %), casein (2.87 %) and dry matter (13.54 %) with regard to milk from the traditional system; respectively: 3.50, 4.31, 2.65 and 13.33 %. With the following stage of lactation, irrespective of the production season, a significant (p≤0.01) increase in the content of protein, casein, fat and dry matter (including non-fat) and systematic decrease in lactose level were stated in milk. The biggest changes were found in milk of cows maintained in the traditional husbandry system, and they were related to protein (an increase by 26 pp.) and casein (by 16 pp.) contents. A significantly (p≤0.05) higher concentration of cholesterol was found in milk of cows from farms with intensive production systems (on average 21.52 mg/100 ml) compared to the traditional (18.69 mg/100 ml). More constant cholesterol content during the whole lactation period was characteristic for milk from the intensive system. Share of large fat globules (a diameter > 10 µm) decreased with the passage of the lactation period in both systems of milk production. In the traditional system, however, these changes were greater, i.e. from 10.17 to 8.06 %, and statistically significant (p≤0.01) in comparison to the intensive system (from 10.42 to 9.01 %).
Key words: milk composition, production system, stage of lactation, technological suitability