Blood analysis showed that supplementation increased the cows' plasma vitamin E levels by 56 percent over control cows', and vitamin E levels in the supplemented cows' colostrum were 39 percent higher than the controls'. Calves from these cows did not have significantly higher levels of serum vitamin E at birth, but after 48 hours their vitamin E levels were 37 percent greater than those of the calves from unsupplemented cows.
Calf immunoglobulin G (IgG) levels were below detection for both groups at birth, but after 48 hours they were two percent greater in calves from the supplemented group--a significant difference, the researchers note.
Other studies have focused on the transition period as the calf's reliance on maternal antibodies diminishes and its own immune system develops, beginning with phagocytic cell activity. Although a few calves retain detectable maternal antibodies in their blood as late as 16 months of age, others lose this immunity by a month of age.
Oregon State University researchers (Nunn et al., 1993) found that IgG concentrations decreased from birth through four weeks of age. IgG concentrations decreased even more in calves with scours, indicating the use of immunoglobulin to combat infection. However, selenium and vitamin E supplementation slowed the decrease in the scouring calves' IgG concentrations, thereby leaving the animals better able to resist infection. In vitro studies by Kansas State University researchers (Eicher et al., 1994) showed an interaction between serum vitamin E levels and the function of leukocytes in three-- and six--week--old dairy calves.
At three weeks of age, neutrophils supplemented with 1,000 µg of vitamin E per deciliter had greater phagocytic capacity, or ability to engulf bacteria and other matter, than did control cells. At six weeks, there was no significant difference in phagocytosis by treatment. However, the chemotactic index, or the speed with which the neutrophils responded to a Staphylococcus aureus assault, was increased with supplementation at six weeks of age.
The researchers suggest that the relationship between phagocytic action and supplementation was due to the antioxidant properties of vitamin E. The researchers suggest that these properties preserved the cell membranes by increasing their stability (thereby leading to improved phagocytosis) but also reduced the superoxide in the cells.
Another Kansas State study (Reddy et al., 1986) also reported enhanced cell-mediated immune response among vitamin E supplemented Holstein heifers. Supplementation was 1,400 IU injected weekly from birth through 12 weeks of age, or 1,400 or 2,800 IU of vitamin E fed orally at weekly intervals.
When averaged across the length of the trial, the lymphocyte stimulation indexes were significantly higher for vitamin E at both the 2,800 IU oral dose and the 1,400 IU injectable dose (Figure 2). Vitamin E at the 2,800 IU oral dose increased serum IgM levels compared to controls. Serum IgG1 and IgG2 levels tended to be greater with vitamin E treatments.
