Biological variations of hematologic and biochemical parameters in cows during early lactation.

The aim of the study was to determine biologic variations of the main parameters in cows in early lactation and to compare intra-individual variations of parameters in cows and other species. 50 cows were included in the experiment. Blood samples were taken at the moment of calving, then on 1st, 7th, 14th and 28th day after calving. CVi had the following values: 1.9-5% for MCV, MCH, MCHC, GLU, TProt, ALB, UREA, Ca, P and Mg; 5.1-10% for RBC, Hgb, Hct, WBC, NEU, LYM, BHB, ALT, CHOL, TGC and >10% for PLT, NEFA, TBil, AST and GGT. For RBC, Hgb, Hct, MCV, MCH subject-based reference values or the reference change value should be used. For all other parameters except AST, population-based reference intervals should be used with caution. For LYM, NEU, PLT, GLU, TProt, ALB, CHOL and TGC index of individuality was close to 0.6 which means that subject-based reference values can be much more adequate to use then population-based reference intervals. For AST population-based intervals should be used. There is little effect of parity (increase CVi with parity) and no effect of milk production. CVi values obtained in cows in early lactation are specific because they deviate from the CVi values of other animal species and human. Calculated RCVs varied from 5.5% for MCHC to 41% for AST. High individuality index for many metabolic parameters opens possibility for development of model for longitudinal monitoring of metabolic status of individual animals during lactation. That requires further research.

Beta-hydroxybutyrate in milk as screening test for subclinical ketosis in dairy cows.

Ketosis is a very frequent metabolic disease in dairy cows, resulting in lower milk production, impaired fertility and increased frequency of other diseases. The course of the disease is often subclinical, so early detection is very important. The aim of the study was to investigate the relation between the concentration of beta-hydroxybutyrate in blood and milk and to determine the cut-off value in milk for detection of subclinical ketosis. The study included 94 cows, which were in the first third of lactation. Beta-hydroxybutyrate (BHB) concentrations were measured in blood and milk serum using a biochemical analyser. The average concentration of BHB in the blood serum samples was 1.14 mmol/L while in the milk it was about ten times lower at 0.117 mmol/L. A statistically significant positive correlation between the concentration of BHB in blood and milk (r=0.705, p<0.001) was found. In cows with BHB in blood below 2.0 mmol/L a stronger correlation between blood and milk BHB was established (r=0.658, p<0.001) than in cows with blood BHB above 2.0 mmol/L (r=-0.292, p=0.206). Therefore, BHB in milk is a very suitable indicator in the diagnosis of subclinical ketosis as there is a good correlation between BHB in the blood and milk of cows with subclinical ketosis. The cut-off concentration of BHB in milk set at ≥0.080 mmol/L (AUC=0.91±0.03; p<0.001) is a significant indicator for subclinical ketosis in dairy cows. The sensitivity of the test was 94% and specificity 74%. Beta-hydroxybutyrate in milk is a good indicator of subclinical ketosis in dairy cows and can be measured accurately with a biochemical analyser.