Effect of daily milk production levels on plasma calcium, phosphorus and magnesium concentrations in dairy cows

The aim of this study was to determine the serum level of calcium (Ca), phosphorus (P) and magnesium (Mg) and hence determine the relationship and the effect of daily milk production on the mentioned essential macro elements. The metabolism and neurohumoral regulation of Ca, P and Mg are closely related, and the metabolic disorder of one of these electrolytes inevitably affects the metabolism of the other two. The study was carried out in the winter period of animal keeping and nutrition, and it included 63 Holstein-Friesian breed cows in the northern region of Bosnia and Herzegovina, aged 2-9 years in different lactation stages (1-8). The largest number of cows, eighteen of them, were in the second, third and fourth lactation stage, while nine cows were in the first lactation stage. This study was conducted on three different groups of cows corresponding to the amount of daily milk production. First was the group of lower daily milk production n=21, the second group of examined cows was the group of medium daily milk production n=23 and third was the group of higher daily milk production n=19. Ca, P and Mg were determined in blood plasma using the Beckmann spectrophotometer. By examining the obtained results and the dynamics of the tested mineral substances, we point out the different behaviour of the Ca-P relationship in correlation with the different level of daily milk produced. Although the average values ​​of both minerals are lowered with an increase in daily milk production, the analysis of single linear regression shows that there is a negative correlation between P concentration in blood plasma and the amount of daily milk produced, while for Ca it has not been established . Although the concentration of Mg in the blood plasma increases as the daily milk production increases, the analysis of single linear regression does not show a significant interconnection of these two values. Lower average values of Ca and P concentrations in the blood of cows with higher daily milk production may be associated with increased total excretion of these minerals through milk, unlike the cows which daily produced lower amounts of milk.