Blood selenium, copper, and zinc in dairy heifers during the transition period and effects of clinoptilolite administration

Selenium (Se), copper (Cu), and zinc (Zn) play important antioxidant role during the transition period of dairy cattle. However, there is limited information about their blood fluctuations during the entire transition period, especially in heifers. Furthermore, it is questionable whether the use of clinoptilolite, a natural zeolite, affects the availability of these trace elements during this period. The objective of the present study was to monitor the blood concentrations of Se, Cu, and Zn during the transition period of dairy heifers and to investigate whether the dietary inclusion of clinoptilolite has any effect on them. Forty clinically healthy Holstein heifers were used in the experiment. They were randomly allocated in two equal groups (n = 20) formed according to their body condition score. The control group was fed only the basal ration whereas the daily feed of treatment group was supplemented with 200 g clinoptilolite. The experiment started 28 days before the expected day of calving and lasted until day 21 after parturition. Blood samples were taken at the onset of the experiment and then at weekly intervals until parturition, at the day of calving, and on days 7, 14, and 21. All samples were analyzed for blood Se and plasma Cu and Zn concentrations. The results indicate that the levels of Se, Cu, and Zn in blood change significantly (P < 0.05) throughout the transition period in dairy heifers and increase significantly (P < 0.05) immediately after calving. Furthermore, the dietary administration of clinoptilolite does not significantly affect their blood concentration (P > 0.05). Blood levels of Se, Cu, and Zn, although undergoing significant changes throughout the transition period in dairy heifers, remain practically stable until parturition and increase significantly immediately after calving. Clinoptilolite does not impair the dietary availability of the trace elements evaluated when added in heifers’ rations during this period.