Change of selenium in plasma of dairy cows receiving two levels of sodium-selenite during the transition period

Abstract

With the aim to study the plasma Se content during transition period, 2 groups of 12 dairy cows were monitored the month before and after calving. In stall 1 (S1) cows were tied and individually fed, in stall2 (S2) cows were free and fed TMR. In both stalls cows were supplied with Se as Na-selenite. In S1 3 mg/d of Se were fed mixed with corn silage while, in S2, Se was offered with TMR, in dry period 2 mg/d were added with a mineral-vitamin supplement, in lactation 2.6 mg/d (when DMI was 22.2 kg/d) with the concentrate. Forages, the same for both stalls, and concentrates were sampled for chemical composition and Se determination. Cows were checked for milk yield and its content of somatic cells (SCC), health problems, and bled for Se determination in plasma. Average Se intake was higher in S1, in both dry (4.08 vs 2.76 mg/d) and lactating (5.80 vs 2.11 mg/d) period. Besides the supplementation, differences depended on high Se intake in S1 with the concentrate (increased after calving to 11.5 kg/DM on d 30 and containing 0.24 mg/kg DM of Se). According to the intake, plasma Se content resulted higher in S1 in dry (1.20 vs 0.74 µmol/L) and lactating (1.47 vs 0.62 µmol/L) cows. In close-up plasma Se decreased in both groups, in first days of lactation increased in S1, while decreased in S2 to level indicating a deficient intake (0.50 µmol/L). These results confirm the link between Se intake and its plasma level. Finally, Se plasma content did not seem related to cow health status during transition period.