The influence of sunflower oil in meals on the blood mineral profile of dairy cows

Minerals are essential substances with an important function in livestock, and their disbalance negatively affects the health and production, especially of ruminants. The addition of fat to the rations of dairy cows impacts the overall and mineral metabolism, and thus on health and production. The aim of the research was to examine the correlative relationships between balanced production meals and the mineral status of lactating cows with different ration compositions with or without the presence of vegetable oil. The research was conducted on 30 dairy cows of the Holstein breed at the Butmir farm, Sarajevo, Bosnia and Herzegovina. Three groups of 10 animals were formed based on productivity (A, 13-15 kg of milk/day, B, 19-21 kg of milk/day and C, 25-27 kg of milk/day). Samples of feed, blood plasma and milk of animals were collected on three occasions a 3-week intervals. According to the feed analysis results, the rations were standardized for each group, given for three weeks without oil,and then for three weeks with the addition of sunflower oil in the amount of 2.5% of the ration dry matter. After determining the content of basic nutrients, dry matter and ash in the rations, the concentrations of Ca, Mg, Na and K were determined by atomic absorption spectrophotometry,while the colorimetric method was used to analyse P according to Woy and Eggertz-Finkener. Analysis of blood mineral parameters was performed spectrophotometrically. The content of fat, proteins, lactose, and non-fat dry matter in milk samples was determined by infrared spectrometry using an automatic analyser. Based on the results, we observed a similarity in changes of values and the statistical significance of the differences in plasma Ca, P and Mg between the study groups and at sampling intervals. Milk production was positively correlated with the concentration of Mg and Ca with addition of the sunflower oil to the meal, while no correlation coefficient was established for P in any of the samplings. Balanced meals with and without the addition of oil did not significantly affect the content of Ca, P or Mg in the blood plasma of the tested animals, nor were significant differences found between the groups. However, by determining the correlations between milk parameters and blood biochemical parameters, a significant positive correlation was established between the amount of milk and Ca and Mg levels with a diet supplemented by oil. Given that the addition of sunflower oil in the amount of 2.5% of dry matter of the balanced rations for cows had no negative effects on the mineral profile and the parameters of the tested animals, we conclude that the introduction of this oil could be useful both from the economic point and improving nutritional composition of milk as an animal food present in the daily human diet.