Energy content and amino acid digestibility of flaxseed expellers fed to growing pigs

This study was conducted to determine the DE and ME as well as the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and AA in flaxseed expellers fed to growing pigs. In Exp. 1, the DE and ME were determined using 66 crossbred growing pigs (Duroc × Landrace × Yorkshire; 54.2 ± 2.3 kg BW) fed 1 of 11 diets in a completely randomized design. The diets included a corn-soybean meal basal diet and 10 experimental diets containing 29.16% flaxseed expellers supplemented at the expense of corn and soybean meal. In Exp. 2, 11 growing pigs (35.5 ± 3.4 kg), fitted with a T-cannula at the distal ileum, were assigned to 6 × 11 Youden square design with 6 periods and 11 diets. The diets included a N-free diet based on cornstarch and sucrose and 10 test diets containing 40% flaxseed expellers as the sole source of AA. Chromic oxide (0.3%) was used as an indigestible marker. There was considerable variation in the chemical composition among the 10 flaxseed expellers. The CV were greater than 10% for ether extract (EE), NDF, ADF, crude fiber, and Ca and ranged from 7 to 12% for the AA. On a DM basis, the DE and ME ranged from 2,786 to 3,730 and from 2,588 to 3,530 kcal/kg, respectively. The apparent total tract digestibility of GE ranged from 59.91 to 75.83% (mean = 70.92%). Ether extract, GE, and NDF were the best predictors to determine DE and ME. The best prediction equations were DE = -3,231 + (1.58 × GE) - (25.79 × % NDF) ( = 0.90) or DE = 4,189 + (56.78 × % EE) - (30.59 × % NDF) ( = 0.85) and ME = -2,968 + (1.47 × GE) - (24.82 × % NDF) ( = 0.85) or ME = 3,931 + (53.77 × % EE) - (29.31 × % NDF) ( = 0.82), respectively. In Exp. 2, there were significant differences in the AID and SID of CP and all AA with the exception of Phe ( < 0.05). The AID and SID of CP averaged 70.16 and 78.04%, respectively. For the indispensable AA, the AID and SID of Thr were the least, with average values of 70.70 and 76.68%, respectively. The digestibility of Arg and Met were the greatest, averaging over 88 and 91% for AID and SID, respectively. The AID and SID of Lys ranged from 66.10 to 81.82% (mean = 74.14%) and from 70.90 to 85.41% (mean = 78.13%), respectively. These results indicate that there is significant variability in chemical composition, energy content, and the SID and AID of CP and AA among the selected flaxseed expellers. The DE and ME of flaxseed expellers are primarily related to their EE and NDF concentrations.