Supplementing selenium yeast to diets with adequate concentrations of selenium: Selenium status, thyroid hormone concentrations and passive transfer of immunoglobulins in dairy cows and calves

The objective of this study was to investigate whether supplementing organic Se yeast to diets with relatively high basal concentrations of Se was more effective than inorganic Se for improving Se status of dairy cows and their calves. Forty Holstein cows (primiparous and multiparous) were fed total mixed rations (TMR) supplemented with 0.3 mg kg-1 of Se (dry matter basis) as either selenized yeast (Se yeast) or sodium selenite from 60 d before the expected calving date until 60 d in milk (DIM). Cows were fed diets containing 0.38 to 0.40 mg Se kg-1 with no supplemental Se for 90 d before receiving the dietary Se treatments. The Se concentration of the TMR supplemented with Se ranged from 0.62 to 0.81 mg kg-1. Blood was collected from cowsat 60 and 30 d before the expected calving date, at calving, and at 15, 30 and 60 DIM, and from their calvesat 24 h and 56 d of age. Milk was collected at calving (colostrum) and at 15, 30 and 60 DIM. At birth, calves were removed from the dam and fed colostrum in an amount equivalent to 10% of their body weight within 12 h. Whole blood Se concentration averaged 11% greater (PB0.05) in cowsfed Se yeast compared with selenite (291 vs. 262±4.5 ng mL-1) and serum Se concentration averaged 13% greater in cows fed Se yeast (128 vs. 113±5.3 ng mL-1). Maternal supplementation of Se yeast increased (PB0.05) the Se status of calves by increasing whole blood (252 vs. 211±16 ng mL-1), serum (94 vs. 75±4.7 ng mL-1), and colostrum (245 vs. 174±5.8 ng mL-1) Se concentration by 19, 25 and 41%, respectively. There was, however, no beneficial effect (P>0.10) of Se source on thyroid hormone concentrations or the passive transfer of immunoglobulins to the calf. Supplemental organic Se yeast increased the Se status of dairy cows and the transfer of Se to their calves even though the Se concentration of the basal diet wasadequate (≥ 0.3 mg kg-1).