Acta Vet. Brno 2007, 76: 553-561
Influences of Different Milk Yields of Holstein Cows on Milk Quality Indicators in the Czech Republic
The milk yield (MY) is an important economic and health factor closely connected with the health status of dairy cows, their reproduction performance, longevity and milk composition and properties (MIs). The differences within MIs between high yielding herd (Group 1; 10 282 kg per lactation) and three herds with average MY (Group 2; 7 926 kg) were tested. The files with 96 and 290 milk samples were collected in summer and winter feeding seasons and well balanced in lactation factors. Group 1 had higher genetical value, better nutrition and was milked three times per day and its MY was higher by 30% (P < 0.001). among 23 milk indicators (MIs) under study only a few MIs (30.4%) were influenced (P < 0.05): somatic cell count (SCC); urea (U); acetone (AC); pH acidity; alcohol stability; curd firmness; the ratio of urea nitrogen in non-protein nitrogen (URN). Except for U, these changes were less important. Protein spectrum was not affected (P > 0.05). The U was probably higher due to higher loading of the nitrogen nutrition (4.27 > 3.57 mmol l-1) in MY 1. Surprisingly, SCC was higher (112 > 81 103 ml-1) and AC lower ((0.0374) 0.0250 < (0.0577) 0.0336 mmol l-1) in Group 1. Both the MIs did not indicate problems of the health status. An indicator of energy nutrition balance as fat/protein ratio was not influenced (1.15 ± 0.24 versus 1.16 ± 0.23; P > 0.05), despite the large difference between MY 1 and 2. URN was higher in MY 1 (46.5 > 39.1%) due to more efficient nutrition, like in U. The high MY had no negative impacts on MIs with well balanced nutrition of Holstein cattle.
