The biological effects of vitamin E are predominantly seen in the prevention of resorption of fetuses, testicular degeneration, muscle dystrophy, anaemia and encephalomalacia, the classical signs of vitamin E deficiency in animals. The influence of vitamin E on the immune system has also become an important issue. Vitamin E acts as an antioxidant but the specific molecular basis of its action is still unclear.
The content of active substances in vitamin E-containing additives depends on the producer, the physical form (liquid or dry) and galenic preparation of the additive therefore varying considerably.
Dry products are mostly in the range of 25 to 55 % active substance, other organic matrix between 46 and 70 % and inorganic matrix (mostly SiO2) between 3 and 50 %. Oily formulations may contain up to 94 % active substance.
The FEEDAP Panel recommends that the vitamin E content should be labelled in IU.
For conversion, the following factors are proposed: 1 mg RRR-α-tocopherol is equivalent to 1.49 IU, 1 mg RRR-α-tocopheryl acetate to 1.36 IU and 1 mg all-rac-α-tocopheryl acetate to 1.00 IU.
Since oily additives may contain up to 94 % RRR-α-tocopherol, their use should be restricted to premixture manufacturers to guaranty homogeneous distribution in final feed.
Considering that (i) high doses of vitamin E may exert inverse responses to the normally described beneficial effects and (ii) the present data are not sufficiently consistent to derive a mandatory maximum content for vitamin E, the FEEDAP Panel recommends to introduce in the register entry for vitamin E, under ‘other provisions’: ‘200 IU vitamin E/kg complete feedingstuffs for all species should normally not be exceeded’.
The following provisions should be made, under ‘description of the additive’:
• All-rac-α-tocopheryl acetate, stabilised, from chemical synthesis;
• RRR-α-tocopheryl acetate, stabilised, extracted from oilseeds;
• RRR-α-tocopherol, stabilised, extracted from oilseeds.