Disclosed is an apparatus when used to promote D-vitamin production in a non-human animal. The apparatus comprises at least one lamp assembly adapted to emit polychromatic light, wherein the polychromatic light emulates natural light. The lamp assembly also emits UV light with enhanced intensity at wavelengths between 270 nm and 315 nm. The at least one lamp assembly comprises at least one medium and/or high pressure lamp. Also disclosed are farms having at least one such apparatus installed and methods of using the apparatus to increase D-vitamin production in a non-human animal.
