Evaluation of energy digestibility of canola coproducts by in vitro analyses and characterization of fat digestion using spectroscopy.

In vitro methods did not accurately predict in vivo apparent total tract digestibility of energy for canola coproducts (r = -0.81; P = 0.002). We scanned 153 samples of digesta, feces, and in vitro digestion residues (ivR) on a Fourier transform midinfrared instrument with a single-reflection attenuated total reflectance attachment. The second derivative spectral net intensities of the carbonyl ester peak at 1745 cm(-1) and olefinic hydrocarbon (=C-H) peak at 3008 cm(-1) were both higher in ivR than in feces (3.83 × 10(-04) vs. 3.46 × 10(-05) and 7.92 × 10(-05) vs. 5.17 × 10(-06), respectively; P < 0.001), indicating poor enzymatic digestion of unsaturated fat. In conclusion, fat digestion of in vitro procedure for canola coproducts requires improvement to adequately mimic in vivo digestion in pigs.