Nutritional value of flaxseed meal for swine and its effects on the fatty acid profile of the carcass1

Four experiments were conducted to determine the nutritional value of flaxseed meal [FSM; 133 g of ether extract (EE) and 343 g of CP/kg of DM] for swine. In Exp. 1, apparent fecal digestibility (AD) of DM and EE, and the DE and NE contents were determined in growing pigs (n = 32; initial BW, 70 +/- 3 kg) and gestating sows (n = 24; parities, 2 to 4). Diets contained 0, 100, 200, or 300 g of FSM/kg at the expense of wheat, barley, and soybean meal. Fecal samples were collected for 3 d after a 9-d adaptation. The AD for DM and EE were 72.0 +/- 0.4% and 67.4 +/- 4.7%, respectively, for growing pigs and 68.0 +/- 0.5% and 48.9 +/- 1.9% for sows. The DE content was 3.51 and 3.54 Mcal/kg for growing pigs and gestating sows, and NE was estimated to be 2.43 and 2.44 Mcal/kg for growing pigs and sows, respectively. Five ileally cannulated barrows (initial BW, 38 +/- 3 kg) were fed semi-synthetic diets containing 400 g of FSM/kg for a 7-d period (4-d adaptation and 3-d collection) then 7 d of N-free diet to determine basal endogenous N losses in Exp. 2. Standardized ileal digestible AA contents were 29.6 +/- 1.0, 5.7 +/- 0.3, 12.1 +/- 0.8, 16.8 +/- 1.0, 10.3 +/- 0.4, 5.3 +/- 0.3, 14.0 +/- 0.7, 9.4 +/- 0.5, 2.9 +/- 0.2, and 13.8 +/- 0.8 g/kg of dry FSM for Arg, His, Ile, Leu, Lys, Met, Phe, Thr, Trp, and Val, respectively. In Exp. 3, the AD of P and the effects of phytase inclusion on P availability were determined. Five groups of 8 barrows (initial BW, 45 +/- 4 kg) were fed a 300 g of FSM/kg semi-synthetic diet with increasing concentrations of exogenous phytase [0, 575, 1,185, 2,400 and 2,570 phytase units (FTU)/kg]. The AD of P increased from 21 to 61% (P < 0.001). Broken-line analysis estimated the optimal phytase inclusion rate to be 1,415 FTU/kg of diet. Growth performance and carcass fatty acid (FA) profiles of pigs fed FSM were determined in Exp. 4. Two hundred pigs (100 barrows and 100 gilts; initial BW, 32 +/- 4 kg), blocked by sex, were housed in groups of 5 pigs per pen and fed 1 of 4 diets containing 0, 50, 100, or 150 g of FSM/kg. Six market pigs per diet were selected for carcass FA analysis. The ADG, ADFI, and G:F were not affected by dietary FSM (P > 0.05). Increasing FSM in the diet from 0 to 150 g of FSM/kg increased the alpha-linolenic acid content from 11.1 +/- 0.2 to 47.4 +/- 1.2 mg/g of backfat (P < 0.001) and from 5.0 +/- 0.1 to 10.1 +/- 0.6 mg/g of loin tissue (P < 0.001). Flaxseed meal despite its deficiency in lysine can be included up to 150 g/kg of diets for swine and will contribute to the enrichment of the carcass with n-3 fatty acids.