Feeding co-extruded flaxseed to pigs: Effects of duration and feeding level on growth performance and backfat fatty acid composition of grower–finisher pigs

To examine the effect of co-extrusion on subsequent n-3 fatty acids in pig tissues, 8 pigs (barrows and gilts) were assigned to either a control treatment or one of nine treatments arranged in a 3 × 3 factorial design with 3 levels of co-extruded flaxseed (5%, 10% and 15%) and 3 durations of feeding (4, 8 and 12 weeks). Feed conversion improved slightly (P = 0.01) with increasing dietary flaxseed but feeding flax for more than 8 weeks reduced average daily gain (P = 0.02). In general, the duration and level of co-extruded flaxseed feeding affected (P < 0.05) most fatty acids except for 22:6n-3 (P > 0.05). Increasing the duration of flax feeding led to significant quadratic effects in backfat 18:3n-3 (P < 0.001) and total n-3 fatty acids (P = 0.002) when feeding 5% co-extruded flaxseed. Those increases were linear (P < 0.001) when feeding 10% and 15% co-extruded flaxseed. Consequently feeding higher levels of flax for shorter periods vs. lower levels for longer periods appears to be more efficient at increasing n-3 fatty acids in pig backfat, but increases appeared to be less consistent. Moreover the addition of a 50:50 mix of extruded flax/peas to pig diets provided a highly available source of 18:3n-3 yielding n-3 fatty acid enrichments in backfat comparable to studies where extracted flaxseed oil was fed. Feeding flax co-extruded with field peas can be used to optimize consistent enrichments of n-3 fatty acids in back fat and relatively small amounts of this fat could be used to manufacture pork products to meet Canadian standards for n-3 fatty acid enrichment.