The relationship between fatty acid and citric acid concentrations in milk from Holstein cows during the period of negative energy balance Vztah mezi obsahem mastných kyselin a kyseliny citronové v mléce dojnic holštýnského skotu v průběhu období záporné energetické laktace

The objective of this study was to determine the relationship between body condition score changes and the dynamics of energy balance indicators fatty acid and citric acid contents in milk during a early part of lactation. In addition, the relationship between these two indicators was also evaluated. A total of 27 Holstein cows that calved within three consecutive weeks were included in the analysis. During the first 17 weeks of lactation, milk samples were collected at a weekly interval and body condition score was assessed once a month. Statistical analyses were performed using Microsoft Office Excel and the procedures MEANS and CORR of SAS 9.1. Trend functions describing the development of fatty acid and citric acid contents explained 67.67 to 92.19 % of their variability. Similar relationships between fatty acid and citric acid contents and the changes in body condition score during the first three months of lactation were observed. In addition, a similar decreasing tendency was also determined for the contents of both the dependent variables in this period. Significant correlations (P<0.01 – 0.001) were calculated (r = 0.51 – 0.74) for lactation weeks 6 and 7, thus before the subsequent decrease of body condition score by 0.2 points between weeks 8 and 12 after parturition. The results indicate the possibility of using the contents of fatty acids and citric acid as indicators of energy balance in dairy cows. The results also confirm the relationships between these indicators and emphasise the importance of proper herd management with respect to body condition score changes and the contents of fatty acids and citric acid in milk.