THE EFFECT OF DIETARY LEVEL OF FAT ON AMINO-ACID DIGESTIBILITIES IN SOYBEAN-MEAL AND CANOLA-MEAL AND ON RATE OF PASSAGE IN GROWING PIGS

The objectives were to determine the effect of fat level on amino acid (AA) digestibility and rate of passage in digesta collected from the ileum. Six barrows, 45 kg, fitted with a T-cannula at the distal ileum were fed three diets that contained 15% crude protein from soybean meal (SBM) and 2, 6 or 10% canola oil (CO), respectively, and 0.5 chromic oxide. The experiment was carried out according to a repeated 3 x 3 Latin square design. The studies were repeated with another six barrows with diets that contained 15% crude protein from canola meal (CM). The pigs were fed 800 g twice daily. The ileal digestibilities (%) of the average of the indispensable AA were 82.5 +/- 2.0, 83.8 +/- 1.9, 85.0 +/- 1.6 and 75.4 +/- 1.9, 72.4 +/- 2.3 and 77.4 +/- 1.9 for the SBM and CM diets with 2, 6 and 10% CO, respectively. The relationship between AA digestibility in SBM and fat level was quadratic (P < 0.05) for most indispensable AA; a curvilinear relationship (P < 0.05) was observed for the CM diets. Dietary fat level had little effect on the fecal digestibilities in SBM and CM. The rate of passage was higher (P < 0.05) for the CM than SBM diets. In conclusion, these studies show that the level of fat may affect ileal AA digestibilities, albeit to a small extent.