154 Reduction of particle size of field peas increases net energy and digestibility of starch when fed to growing pigs

Abstract Two experiments were conducted to test the hypothesis that particle size of field peas and location of production may affect the apparent ileal digestibility (AID) of starch, the standardized ileal digestibility (SID) of amino acids (AA), and net energy (NE). One source of peas from the U.S., and two sources from Canada were procured. The U.S. peas were ground to 265, 457, or 678 µm, whereas the two Canadian peas were ground to 411 and 415 µm, respectively. A basal diet containing corn and soybean meal as the sources of energy, starch, and AA, and five diets containing corn and soybean meal and 50% of each source of peas were formulated. Pigs were fed the same diets in Exp. 1 and 2, but an N-free diet was also used in Exp. 1. In Exp. 1, barrows n = 7; initial body weight (BW) = 60.6 kg; SD = 2.1 that had a T-cannula installed in the distal ileum were allotted to a 7 × 7 Latin square design with seven diets and seven periods. Ileal digesta were collected and analyzed for Cr and AA. In Exp. 2, pigs (n = 24; initial BW = 30.8 kg; SD = 1.0) were used in a 6 × 6 Latin square design with six calorimetry chambers and six periods. To determine NE, feces and urine were quantitatively collected and O2 consumption and CO2 and CH4 productions were measured. In both Exp. 1 and 2, the statistical model included diet as the main effect and pairwise comparisons were used to separate the means. Contrast coefficients were also used to determine linear effects of particle size within the U.S. peas. Results from Exp. 1 indicated that the SID of AA was not influenced by the origin of the peas or by particle size, except that the SID of Arg was linearly (P = 0.042) increased (Table 1) as particle size of U.S. field peas was reduced. The AID of starch in the U.S. peas ground to 265 µm was greater (P 0.05) than in the two Canadian sources, and the AID of starch and NE in diets were linearly (P 0.001) increased as particle size was reduced. The NE in U.S. peas ground to 678 µm was less (P 0.05) than in all other pea samples. In conclusion, AID of starch, SID of AA, and NE did not differ between field peas grown in Canada and peas grown in the U.S., but reducing the particle size of field peas resulted in improved digestibility of starch and energy by pigs.