Thesis (M.S., Animal and Veterinary Science) -- University of Idaho, 2016 | The objective of this study was to increase the alpha-linolenic acid (ALA) concentration in milk fat by feeding a rumen protected flax-based (RPF) supplement. Eight lactating cows were randomly assigned to four treatment sequences in a replicated 4 x 4 Latin Square design with 16 d periods. The four treatments were 0, 1, 2, and 3 kg of RPF added to a base ration daily. Milk samples were collected on d 15 and 16 of each period. RPF did not affect dry matter intake, milk yield, or most milk components. Many fatty acids in milk were altered by treatment with generally decreased short- and medium-chain saturated fatty acids and increased long-chain fatty acids. RPF increased ALA in milk linearly with a 5-fold greater concentration in cows fed 3 kg/d of RPF compared to the unsupplemented control. This novel rumen protected ALA source enriched milk ALA greater than any previous method.