Flax was first brought to North America for its stem fiber, which was used in the making of linen and paper. Today flax is grown in the United States and Canada as a commercial oil crop. Linseed oil is pressed from flaxseed and further extracted with a petroleum solvent. Industrial linseed oil is not suitable for animal or human consumption. The flaxseed that remains after oil extraction can be made into meal suitable for use in animal feeds.
Flaxseed is unique among oilseeds because it is high in alpha-linolenic acid. Flax is one of the most concentrated sources of unsaturated fatty acids available in poultry feedstuffs. Oil composes 35% to 45% of the content of flaxseed, and 45% to 52% of the oil is alpha-linolenic acid.
Flaxseed is used in the United States and Canada in the production of eggs enriched with omega-3 fatty acids. The increase in polyunsaturated fatty acids is accompanied by a decrease in saturated fatty acids. The result is a healthier fat profile. Feeding flaxseed to laying hens results in a six- to eight-fold increase in the omega-3 fatty acid content of eggs. Such eggs are equivalent to 113 g (4 oz) of cold-water fish as a source of the omega-3 fatty acids.
While feeding poultry a diet composed of 10% flax results in significantly higher levels of omega-3 fatty acids in hens laying brown and white eggs, long-term use of flaxseed has been shown to increase the level of liver hemorrhages in laying hens. The cause of the hemorrhages is unclear. Researchers hypothesize that the livers of flax-fed birds contain more long-chain unsaturated fatty acids, which are more prone to oxidative rancidity.
Feeding flaxseed to broilers seven days prior to slaughter increases the omega-3 content of the meat. The linolenic acid is preferentially increased in dark meat, while long-chain omega-3 fatty acids increase preferentially in white meat.
Enzyme addition and feed pelleting are reported to improve the nutritive value of flaxseed for broiler chickens. The addition of enzymes that break down carbohydrates has been shown to improve the energy utilization from full-fat flaxseed, enhancing its feeding value for poultry. Research has shown that replacing the corn in layer diets with pearl millet reduces the amount of flaxseed needed to obtain omega-3-enriched eggs.
Coccidiosis, caused by several species of Eimeria (protozoa), is a problem in many broiler operations. Feeding diets supplemented with omega-3 fatty acids suppresses the development of Eimeria tenella but is not beneficial in reducing E. maxima levels, and may actually make lesions worse at high-parasite doses.