THE PREDICATIVE VALUE AND CORRELATIONS OF TWO MILK INDICATORS IN MONITORING ENERGY METABOLISM OF TWO BREEDS OF DAIRY COWS

Ketosis is a disorder of energy metabolism in dairy cows. It deteriorates milk yield, quality and reproduction and can have a fatal impact on animal. Milk acetone (AC) in combination with fat/crude protein (F/CP) ratio could represent good ketosis indicators. Prevention of dissease is very important in practice. 960 individual milk samples (MSs) from the Holstein (H) and Czech Fleckvieh (C) dairy cows (1 : 1), their whole lactations and summer and winter seasons of three years were analysed. Milk yield of seven included herds varied from 5,500 to 10,000 kg. AC values were logarithmically transformed. Impacts of breeder factors on AC and F/CP were evaluated by statistical parameters and regression analyse. AC levels differed insignificantly (P 0.05) between H and C breed in whole lactation (1.87 and 1.70 mg.l^–1 as geometrical means) but differed significantly (P 0.05) in the first third of lactation (FTL; 2.20 1.72 mg.l^–1). F/CP did not differ between breeds. The significant differences were not recorded beween winter and summer seasons for both indicators. AC and F/CP are good indicators for monitoring and prevention of subclinical ketosis in dairy cows because of good correlations between them (0.23, 0.28 H, 0.19 C; P 0.001), especially in FTL (0.33 /n = 329/, 0.36 H, 0.30 C; P 0.001). Indicators correlated more in summer than in winter season (0.38 0.29, P 0.001, in FTL). The closest relationship was found in H cows in FTL in summer (0.48, P 0.001). Discrimination limits for subclinical ketosis, which were derived for F/CP via model according to relevant AC threshold (10 mg.l^–1) via suitable equations, could be 1.32 and 1.42 (H) and 1.27 and 1.52 (C) for the first and other lactations. Results could be used in practical advisory service for support of good milk quality and adequate dairy cow health, reproduction performance and longevity