Tocopherols and tocotrienols in serum and liver of dairy cows receiving conjugated linoleic acids or a control fat supplement during early lactation

The fat-soluble vitamin E comprises the 8 structurally related compounds (congeners) alpha-, beta-, gamma-, and delta-tocopherol (with a saturated side chain) and alpha-, beta-, gamma-, and delta-tocotrienol (with a 3-fold unsaturated side chain). Little is known regarding the blood and liver concentrations of the 8 vitamin E congeners during the transition from pregnancy to lactation in dairy cows. We thus quantified tocopherols (T) and tocotrienols (T3) in serum and liver and hepatic expression of genes involved in vitamin E metabolism in pluriparous German Holstein cows during late gestation and early lactation and investigated whether dietary supplementation (from d 1 in milk) with conjugated linoleic acids (CLA; 100 g/d; each 12% of trans-10,cis-12 and cis9, trans-11 CLA; n = 11) altered these compared with control-fat supplemented cows (CTR; n = 10). Blood samples and liver biopsies were collected on d 21, 1, 21, 70, and 105 (liver only) relative to calving. In both groups, the serum concentrations of alpha T, gamma T, beta T3, and delta T3 increased from d -21 to d 21 and remained unchanged between d 21 and 70, but were unaffected by CLA. The concentrations of the different congeners of vitamin E in liver did not differ between the CTR and the CLA groups. In both groups, the concentrations of the vitamin E forms in liver changed during the course of the study. The hepatic mRNA abundance of genes controlling vitamin E status did not differ between groups, but alpha-tocopherol transfer protein and tocopherol-associated protein mRNA increased with time of lactation in both. In conclusion, the concentrations of vitamin E congeners and the expression of genes related to vitamin E status follow characteristic time-related changes during the transition from late gestation to early lactation but are unaffected by CLA supplementation at the dosage used.