Reduction of particle size of field peas (Pisum sativum L.) increases net energy and digestibility of starch when fed to growing pigs, but there is no difference in nutritional value between peas from the U.S. and peas from Canada.

Abstract

Two experiments were conducted to test the hypothesis that particle size of field peas and location where peas are grown do not affect apparent total tract digestibility (ATTD) of nutrients and gross energy (GE), digestible energy (DE), metabolizable energy (ME), and net energy (NE), apparent ileal digestibility (AID) of starch, or standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA). In both experiments, three sources of field peas were used. One source was obtained from the U.S., and two sources were obtained from Canada (i.e., Canada 1, Canada 2). The U.S. field peas were ground to 678, 457, or 265 µm, whereas the two sources of Canadian peas were ground to 411 and 415 µm. Therefore, five batches of field peas were used in both experiments. A basal diet contained corn and soybean meal as the only source of energy, starch, and AA, and five diets containing corn and soybean meal and 50% of each source of field peas were also formulated. The ratio between corn and soybean meal was 1.92:1 in all diets. In Exp. 1, an N-free diet was also used to calculate basal endogenous losses of AA and CP, but in Exp. 2, no N-free diet was used. In Exp. 1, seven barrows (initial body weight = 60.6 ± 2.1kg) 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. In Exp. 2, twenty-four pigs (initial body weight = 30.8 ± 1.0kg) were housed in six calorimeter chambers with four pigs per chamber. The six chambers were allotted to one of the six diets using a 6 × 6 Latin square design with six consecutive periods of 15 d. Results of Exp. 1 demonstrated that the SID of CP and AA was not influenced by the origin of the peas or by the particle size, but the AID of starch increased (linear, P < 0.001) as particle size was reduced from 678 µm to 457 or 265 µm. Results of Exp. 2 indicated that growing location did not affect concentrations of DE, ME, or NE of field peas, but concentrations of DE, ME, and NE increased (linear, P < 0.05) when the particle size was reduced from 678 µm to 457 or 265 µm. In conclusion, field peas grown in Canada or the U.S. have the same nutritional value, but starch digestibility and NE increase if the particle size of field peas is reduced.