Interpretive Summary: Impact of ileal indigestible protein on fecal nitrogen excretion and fecal microbiota may be greater compared with total protein concentration of diets in growing pigs

By: Jung Yeol Sung, Timothy A Johnson, Darryl Ragland, Olayiwola Adeola

Dietary protein concentration has been gradually reduced because reductions in protein concentration in swine diets are known to be beneficial in terms of feed costs, nitrogen excretion, and intestinal microbiota. However, ileal indigestible protein concentration may be more influential in those variables of pigs compared with total protein concentration in diets because ileal indigestible protein considers both protein concentration and digestibility of diets. In the current study, three diets were prepared: 1) corn-soybean meal diet, 2) high-indigestible protein diet replacing soybean meal in the first diet with autoclaved soybean meal, and 3) high protein diet where the inclusion rate of soybean meal was greater than that of the other diets. The experimental diets were fed to cannulated pigs and ileal digesta and fecal samples were collected. Fecal nitrogen output was greater in pigs fed the high-indigestible protein diet. Fecal microbiota was shifted by the high-indigestible protein diet, and this shift may not be beneficial. In conclusion, the impact of changes in ileal indigestible protein on fecal nitrogen excretion and fecal microbiota may be greater compared to changes in total protein concentration of diets in growing pigs.