Two in vitro experiments were conducted to investigate the effects of choline chloride, copper sulfate (CuSO4) and zinc oxide (ZnO) on the stability of vitamin A (VA), vitamin D3 (VD3), vitamin E (VE), vitamin K3 (VK3), vitamin B1 (VB1), vitamin B2 (VB2), vitamin B6 (VB6), niacin, and pantothenic acid in vitamin and vitamin/trace mineral (VTM) premixes for weanling piglets after 0, 1, 2, 3, 6 and 12 months of premix storage. We developed predicted equations to estimate vitamin retention during storage. Two vitamin premixes (with or without choline) were formulated and stored at 25 °C and 60% humidity to establish the storage stability of vitamin premixes. Additionally, four VTM premixes were used to evaluate the effect of choline chloride (0 vs. 40,000 mg/kg) and trace minerals (Low CuSO4 + ZnO vs. High CuSO4 + ZnO) on vitamin stability in VTM premixes stored at room temperature (22 °C). In general, as storage time increased, residual vitamin activity decreased (p < 0.05). The results confirmed that VD3, VE, VB2, VB6, niacin and pantothenic acid were highly stable during storage, while the retention of VA, VK3 and VB1 was significantly affected by storage time and the presence of choline and high concentrations of Cu and Zn in the premix. After one year of storage, the retention of VE, VB2, VB6 niacin, and pantothenic acid was more than 90% in vitamin and VTM premixes. The retention of VD3 was more than 90% in vitamin premixes and more than 80% in VTM premixes after one year of storage. We conclude that current microencapsulation techniques for vitamin premixes appear to be inadequate to guarantee VA, VK3, and VB1 concentrations in VTM premixes.
Keywords: choline chloride; copper sulfate; microencapsulated vitamins; premixes; stability; zinc oxide.