Vitamin E
Vitamin E is an important lipid soluble antioxidant that protects against free radical-initiated lipid peroxidation (Halliwell and Fresh green forage is an excellent source of vitamin E. However, concentrates and stored forages (hays, haylages, and silages) are generally low in vitamin E A number of studies have documented that plasma concentrations of a-tocopoherol or vitamin E can decrease dramatically in dairy cows fed stored forages during the peri parturient period. In these studies cows were fed alfalfahay , corn silage and alfalfa hay, or a combination of corn silage, hay,
and haylage as the forage source.The lowest plasma a-tocopherol concentrations are gener-ally observed between 1 week pre-partum and 2 week spost-partum. In cows fed stored forages, relatively high supplemental levels of vitamin E (3000–4000 IU/day) are needed to prevent the drop in plasma a-tocopherol concen-trations around parturition mately1.6 IU of supplement Dairy cows fed stored forages require approxial vitamin E/kg BW (approximately80 IU/kg DM intake) during the dry period to maintainplasma a-tocopherol at concentrations (approximately3.0 lg/mL) that maximize health and immune function. This level of supplemental vitamin E willmitigate but not totally prevent a drop in plasma a-tocoph-
erol around parturition