Objective: The aim of the study was to investigate possible associations between the energy balance of dairy cows and the differential cell count in milk. Such associations could be used for the assessment of the mastitis risk due to metabolic stress.
Material and methods: In 15 red Holstein cows, samples were collected in the 2nd, 6th and 12th week post partum. To reflect the energy balance of the cows, the following parameters were evaluated: β-hydroxybutyric acid (BHB) in serum, fat-protein-ratio (FEQ) in milk at times of examination and difference of the body condition score (DBCS) between times of examination. The overall somatic cell count (SCC) and the differential cell count were determined. Measuring the differential cell count, comprising fractions of lymphocytes (LYM), macrophages (MAK), polymorphonuclear leucocytes (PMN) and epithelial cells (EPI), was carried out using indirect immune fluorescent staining in combination with propidium iodide staining. The interrelationships between parameters of energy status and milk cells were statistically assessed using correlation analysis. Data which were not normally distributed were transformed using logarithms (log). A mixed model was used to test the associations between milk cell parameters and the parameters of energy balance, using the animal as a random effect.
Results: There was a significant correlation between FEQ and SCClog as well as between DBCS and SCClog (FEQ: r=0.459, p<0.01; DBCS: r=-0.301, p<0.05). Similarly directed correlations were found between both parameters of energy balance and LYMlog (FEQ: r=0.530, p<0.01; DBCS: r=-0.318, p<0.05) and MAKlog (FEQ: r=0.520, p<0.01; DBCS: r=-0.299, p<0.05). Univariate analysis provided the highest correlations between LYMlog and FEQ and between MAKlog and FEQ (LYMlog: F=17.36, p<0.01; MAKlog: F=14.46, p<0.01).
Conclusion: The results of the study indicate associations between energy balance and the differential cell count in milk.