- Flax seed is a rich source of alpha-linolenic acid (ALA). Feeding broiler birds flax seed can increase n-3 fatty acids (FA) in meat tissues and can increase human intake of n-3 FA. However, non-starch polysaccharides (NSP) in flax seed decrease digestibility of lipids and proteins and have a negative impact on bird performance. Addition of carbohydrase enzymes to flax-based broiler diets can decrease the effects of NSP. Two experiments were conducted to investigate the effect of flax seed and carbohydrase enzyme on bird performance, tissue FA composition, meat lipid quality, lipid metabolism, and foregut morphology. In Experiment 1, 120 four-day-old broiler chicks were assigned to one of three treatments: Control (corn-soybean meal), Flax (Control adjusted for 15% flax), and Flax+E (Flax+0.05% enzyme). Birds received the diets for 35 days and tissues (breast and thigh muscle, liver, heart, abdominal fat pad) were collected. Compared to Control, flax-fed birds had higher body weight (p<0.037), average daily gain (ADG) (p<0.034), and lower feed:gain (p=0.01). In breast and thigh muscle from Flax 15+E, there was an increase in ALA (p<0.001) and total n-3 FA (p<0.001). Over 7.9- and 24-fold increases in long chain (LC) n-3 FA were observed in thigh and breast tissue of Flax+E birds compared to Control (p<0.001). Total n-3 FA were higher in the liver and heart of Flax+E relative to Flax and Control (p<0.002) along with a decrease in saturated FA (p=0.001). Total lipids were lowest in heart (p=0.022) and adipose tissue of Flax (p=0.034). No difference was observed in total lipids or lipid oxidation products measured as thiobarbituric acid reactive substances (TBARS) in liver, breast, and thigh tissues. Experiment 2 evaluated the interaction of flax (high, low) and enzyme supplementation (with, without). A total of 112, five-day-old broiler chicks were assigned to one of four treatments: Flax 10 (corn-soybean meal basal diet adjusted for 10% flax), Flax 15 (basal diet adjusted for 15% flax), Flax 10+E (Flax 10+0.05% enzyme), and Flax 15+E (Flax 15+0.05% enzyme). Birds received the diets for 40 days and tissues (breast and thigh muscle, liver, heart, abdominal fat pad) were collected. All parameters were analyzed with two-way ANOVA. Dietary flax level and enzyme did not affect body weight, feed consumption, or ADG during the starter phase. However, final body weight and overall weight gain and ADG were highest in high flax-fed birds (p=0.005). No effect of diet on relative organ weights was observed. High flax led to a decrease in total lipids in thigh, breast, and liver tissues (p<0.05) while enzyme supplementation led to a decrease in total lipids in heart tissue (p=0.002). Total lipids were a poor predictor of lipid oxidation. TBARS were increased in liver tissue with high flax (p=0.018) and decreased in breast tissue with high flax (p=0.031). There was no difference in TBARS results in thigh tissue. In thigh and breast muscle, there was no effect of flax level or enzyme on relative percentage of total n-3 FA, LC n-3 FA, or monounsaturated FA. In heart and liver tissues, flax level and enzyme supplementation led to an increase in oleic acid (18:1) and palmitic acid (16:0) (p<0.04) and a decrease in arachidonic acid (p<0.04). There was a trend for a decrease in DM of excreta with enzyme addition. Addition of enzyme led to large increases in villi height, villi width, and crypt depth in the jejunum in the starter phase (p<0.04). It is concluded that addition of carbohydrase enzymes increases the availability of ALA and higher levels of flax have a larger impact on hepatic and cardiac tissues than muscle tissues. Feeding broilers diets containing whole flax seed with carbohydrase enzymes can provide the consumer with a poultry meat product that is enriched in LC n-3 FA without depressing growth performance of the birds. We estimate the cost of feeding a broiler bird 15% whole flax seed and 0.05% carbohydrase enzyme mixture for a standard 42-day growth period to be $0.50 per pound of processed meat; some if not most of these costs would be offset by a reduction in corn and other feed ingredients. A serving (100 g) of skinless breast from this bird could provide 18% of the recommended daily intake of LC n-3 PUFA. A serving (100 g) of skinless thigh could provide 25% of the recommended daily intake of LC n-3 PUFA and would meet international food labeling requirements for labeling as an "enriched" consumer product.