Although various feed grains and by- products contain natural vitamins, many are destroyed when the kernel is damaged or consequently cracked. Purchasing a properly fortified vitamin premix is only part of the job in providing the correct nutrition to the pig.
Vitamin stability within the premix and after the diet is mixed varies greatly between vitamins. This is largely dependent on the various conditions of where and how the vitamin premix is stored. Moisture, heat, and the contact of vitamins with trace minerals are the most common reasons why vitamin stability is reduced. Choline chloride is hygroscopic, and when added to a vitamin premix it will generally hasten the rate of other vitamin destruction. Vitamin premixes should be stored in a cool, dark, dry location. Storage length of vitamin premixes should not exceed three months. The more stable vitamins have potency losses of less than 1% per month. The less stable vitamins may have losses of 4 to 6% per month but could be as high as 15 to 30%, particularly when mixed with trace minerals. Pelleting will cause vitamin destruction with stable vitamins having losses of 2 to 6% per month, while less stable vitamins lose 10 to 25% of their activity.