Flaxseed extrusion and expansion coupled with enzyme and pelleting changed protein and lipid molecular structure of flaxseed and improved digestive enzymes activity, intestinal morphology, breast muscle fatty acids and performance of broiler chickens

•EPF increased BW and reduced FCR compared to the RF and ETF throughout the experimental period.•EPF and ETF reduced α-helix and increased ß-sheet height and increased CH3 asymmetric stretching compared to raw flaxseed.•Lipase and alkaline phosphatase activity were increased when chicks were fed with diets containing EPF and ETF.•Long chain n-3 fatty acids were increased and n-6 to n-3 ratio was reduced by inclusion of flaxseed. An experiment was performed as a completely randomized design in a 4 × 2 × 2 factorial arrangement with 4 replicates of 15 chicks in each pen to investigate the effects of flaxseed extrusion and expansion accompanying with enzyme addition in mash or pelleted diets on protein and lipid molecular structure spectral and performance characteristics of broiler chickens. Factors included were four types of flaxseed: control (corn-soybean meal based diet with no flaxseed), raw flaxseed (RF, 200 g/kg), extruded flaxseed (ETF, 200 g/kg) and expanded flaxseed (EPF, 200 g/kg); two levels of carbohydrase enzyme (0 or 25 mg/kg) and two forms of diet (pellet or mash). Performance criteria, protein and lipid molecular structures, blood biochemical characteristics, digestive enzymes activity and nutrient digestibility, cecal microbial population and breast muscle fatty acids profile were evaluated during the trial. EPF increased BW and reduced FCR compared to the RF and ETF throughout the experimental period (0–28 d., P ≤ 0.001). Pelleting the diets increased BW, improved feed consumption and reduced FCR in comparison to the mash diets fed chicks (P ≤ 0.001). Enzyme addition had no impact on BW, FCR and feed intake of chickens. Both EPF and ETF reduced α-helix and increased ß-sheet height and increased CH3 asymmetric stretching compared to raw flaxseed (P