Standardized total tract digestibility of phosphorus in field peas fed to growing pigs is increased by microbial phytase, but particle size and origin of field peas do not affect digestibility of phosphorus

Two experiments were conducted to test the hypothesis that particle size or origin of field peas does not influence apparent total tract digestibility (ATTD) or standardized total tract digestibility (STTD) of P, but that increasing levels of phytase will increase ATTD and STTD of P in field peas when fed to growing pigs. In experiment 1, one source of field peas was obtained from the U.S., and two sources were obtained from Canada (i.e., Canada 1 and Canada 2). The U.S. field peas were ground to 265, 457, or 678 µm, whereas the Canada 1 peas were ground to 253 µm, and the Canada 2 source was ground to 411 µm. The five batches of field peas were each included in one diet and fed to 50 growing pigs (16.36 ± 1.19 kg) with 10 replicate pigs per diet. In experiment 2, six diets based on the U.S. field peas ground to 678 µm were formulated to contain 0, 250, 500, 1000, 2000, or 4000 units per kg of microbial phytase and fed to 48 pigs (15.26 ± 0.91 kg) with eight replicate pigs per diet. In both experiments, field peas were the only source of P in the diets. Pigs were housed individually in metabolism crates and feces were collected for four days. Results of experiment 1 indicated that the ATTD and STTD of P were not affected by source of peas or by particle size of the field peas and it was concluded that growing location and variety do not influence STTD of P in field peas. Results of experiment 2 indicated that the ATTD of Ca and P and the STTD of P increased (linear, P < 0.001) as phytase increased in the diets, and fecal excretion of Ca and P was reduced as the concentration of dietary phytase increased (linear, P < 0.001). It was, therefore, concluded that if microbial phytase is included in diets containing field peas, the inclusion of feed phosphate can be reduced, and manure concentration of P will also be reduced. In conclusion, the hypotheses that neither growing location nor particle size influences STTD of P were confirmed, and the hypothesis that increased concentration of dietary phytase increases STTD of P was also confirmed.