By Søren Krogh Jensen & Charlotte Lauridsen
Speaker: Søren Krogh Jensen, PhD
Senior Researcher - Molecular Nutrition & Reproduction
Department of Animal Science
Aarhus University, Aarhus, Denmark
Vitamin E is a very important antioxidant for livestock and especially for young animals it serves as an important modulator in the maturation of the immune system. Traditionally, vitamin E is added to the diet as synthetic all-rac-α-tocopheryl-acetate. In the intestine this ester of α-tocopherol is incorporated into the mixed micelles of bile acids – phospholipids, free fatty acids and mono-, di- and triglycerides. This incorporation is a prerequisite for proper enzymatic action of the intestinal lipases secreted from the pancreas on the components in the micelles. It is generally accepted that animals have adequate capacity for hydrolysing tocopheryl esters and other vitamin esters. However, in Denmark it was noticed that after the ban of antibiotic growth promoters in feed, the incidence of vitamin E deficiency, especially among newly weaned piglets was increased. Digestibility experiments showed very low absorption (20-30%) of synthetic all-rac-α-tocopheryl-acetate. Therefore, approaches that can increase vitamin E status was warranted. Also for the newborn vitamin E is very important, as the placental transfer is limited and neonates are born with a very low vitamin E status. Colostrum and milk is therefore an important source of vitamin E (α-tocopherol) to the newborn. Composition of mother milk in terms of lipid-soluble compounds is highly influenced by the maternal diet, and it is known that the vitamin E status of the milk is influenced by both the quantity and the quality of the vitamin E in the maternal diet. Vitamin E is most often added to the feed as synthetic all-rac-α-tocopheryl acetate. The synthetic form consists of an equal amount of 8 stereoisomers of α-tocopherol, while α-tocopherol synthesized by nature always possess the RRR configuration. Several investigations have shown a higher utilization of the natural form of vitamin E compared to the synthetic form, caused by a biodiscrimination within the animals. In experiments the transfer of the different isomers of α-tocopherol from feed to mother, milk and progeny was studied. Analysis of the vitamin E content and the stereochemical composition of α-tocopherol showed that the natural isomer was the dominating isomer in plasma and milk from the mothers as well as in plasma and tissues from the progeny. Based on the relative abundance of the different stereoisomers it can be calculated that sows and mink utilize RRR-α-tocopherol by a factor 2-3 times better than all-rac-α-tocopherol and data indicate that cows favour the natural isomer even further.