Means to improve the nutritive value of flaxseed for broiler chickens: the effect of particle size, enzyme addition, and feed pelleting.

Three experiments were conducted to explore dietary means (particle size, enzyme addition, bile salts addition, and feed pelleting) of minimizing the antinutritive effects of cell wall-nonstarch polysaccharides of flaxseed. Broiler chickens were fed corn-soybean meal-based diets containing 15% of full-fat flaxseed from 5 to 18 d. The effects of 2 enzyme preparations containing viscosity-reducing or cell wall-degrading activities on growth performance and nutrient digestibility were evaluated in experiment 1. Enzyme addition had beneficial effects (P<0.05) in increasing nonstarch polysaccharide digestibility and reducing intestinal viscosity. However, no differences in growth performance or fat digestibility were observed between the enzyme types. Therefore, the enzyme supplement containing both viscosity-reducing and cell wall-degrading activities was used in subsequent studies. A 2x2x2 factorial arrangement was used in experiment 2 to investigate the effects of particle size (coarse vs. fine), enzyme supplementation, and bile salt addition on the nutritive value of flaxseed for broiler chickens. In experiment 3, a 4x2 factorial arrangement was used to further investigate the effects of feed processing (whole seed, coarsely ground seed, and finely ground seed in pelleted diets or finely ground seed in mash diets) and enzyme addition on growth performance and fat utilization. Bile salt addition did not improve fat digestibility. Particle size reduction via grinding had no significant effect on growth performance no matter if present in the mash or pelleted diets. When compared with grinding, feed pelleting showed more pronounced and beneficial effects on growth performance particularly when whole, intact seeds were used, indicating a potential for using whole flaxseed in the pelleted diets. Enzyme addition resulted in an increase in total tract fat digestibility by 3 to 6%, which was reflected in an improved feed conversion ratio by 1 to 3%, regardless of the processing method used (P<0.05). In conclusion, enzyme addition and feed pelleting offer practical solutions to improve the nutritive value of flaxseed for broiler chickens.