Effects of supplementing mid-lactation dairy cows with seaweed and vitamin E on plasma and milk α-tocopherol and antibody response to immunization

Summary

The objective of the current experiment was to compare the effects of supplementing mid-lactation dairy cows with
all-rac-α-tocopheryl acetate (SyntvE), RRR-α-tocopheryl acetate (NatvE) or seaweed meal (Seaweed) in the presence
of a Control group (no supplemental vitamin E or seaweed) on the concentration of α-tocopherol in plasma and
milk, and antibody response following immunization. The hypothesis was that supplementation of dairy cows
with vitamin E, regardless of its form, would increase plasma and milk α-tocopherol compared to the control
diet and this incremental response would be bigger with NatvE than SyntvE. Furthermore, it was hypothesized
that vitamin E, regardless of its form, will provide an improved adaptive immune response to immunization
than the Control diet, and cows supplemented with Seaweed meal would produce better adaptive immune
response following immunization than cows in the Control group. Twenty-four Norwegian Red (NR) dairy
cows in their mid-lactation were allocated randomly to the four treatments in a replicated Latin square design.
The cows were fed on a basal diet of silage and concentrate on top of which the experimental supplements
were provided. Plasma and milk α-tocopherol concentrations were higher in NatvE and SyntvE groups than in
the other two groups. The RRR-α-tocopherol stereoisomer was the predominant form (>0·86), in both plasma
and milk, whereas the remaining part was largely made up of the other three 2R stereoisomers (RRS, RSR and
RSS). In cows fed the Control, Seaweed and NatvE, the proportion of the RRR-α-tocopherol stereoisomer in
plasma and milk constituted >0·97 of the total α-tocopherol. Mid-lactation NR dairy cows had higher than
adequate levels of plasma α-tocopherol (9·99 mg/l) even when not supplemented with external source of
vitamin E, suggesting that with a good quality silage these cows may not be at risk of vitamin E deficiency.
Furthermore, the present study shows that dairy cows in mid to late lactation have preferential uptake of RRR
stereoisomer of α-tocopherol compared with other stereoisomers. All cows responded well to immunization
with different antigens, but there were no significant group effects of the diet on the immune response measured.