Acta Vet. Brno 2007, 76: 563-571
Impact of Different Milk Yields on Milk Quality in Bohemian Spotted Cattle
The milk yield (MY) is a significant economic and health factor. MY influences the health state of dairy cows, their reproduction performance, longevity and milk indicators (MIs). Differences within MIs between 2 higher (1; 8 348 kg per lactation; 240 individual milk samples) and 2 lower yielding herds (2; 7 344; 239) of Bohemian Spotted dairy cows (B) were tested. Sampling was carried out during summer and winter feeding seasons. Lactation factors were well balanced. Group 1 was on a higher genetical level, had better nutrition and higher MY by 13.7% (P < 0.001). All herds were milked twice a day. Twenty-three MIs were examined and 39.1% (9 of 23; 30.4% it was formerly in Holstein (H) with higher MY by 30%) were influenced (P < 0.05) by relatively smaller difference in MY: fat; log somatic cell count; urea (U); acetone (AC); alcohol stability; time for enzymatic coagulation; whey volume; ratio of urea nitrogen in nonprotein nitrogen (URN); fat/protein content ratio. It shows a higher susceptibility of B cows to the impact of higher MY on lactation physiology than H. Most changes were in more important MIs, usually with higher differences compared with H. The whole milk protein spectrum was not influenced (P > 0.05). The U was higher (5.707 > 4.365 mmol l-1) in group 1, AC and URN as well (0.0362 > 0.0238 mmol l-1 and 51.94 > 41.97%). It corresponds with nitrogen and energy metabolism.
