Ileal and total tract nutrient digestibilities and fecal characteristics of dogs as affected by soybean protein inclusion in dry, extruded diets

Plant-based protein sources are generally less variable in chemical composi tion than animal-based protein sources. However, relatively few data are av ailable on the nutrient digestibilties of plant-based protein sources by co mpanion animals. The effects of including selected soybean protein sources in dog diets on nutrient digestion at the ileum and in the total tract, as well as on fecal characteristics, were evaluated. Six protein sources were used: soybean meal (SBM), Soy-afluff 200W (soy flour), Profine F (tradition al aqueous-alcohol extracted soy protein concentrate [SPC 1]), Profine E (e xtruded SPC [SPC 2]), Soyarich I (modified molecular weight SPC [SPC 3]), a nd poultry meal (PM). All diets were extruded and kibbled. Test ingredients varied in CP and fat contents; however, diets were formulated to be isonit rogenous and isocaloric. Nutrient intakes were similar, except for total di etary fiber (TDF), which was lower (P < 0.01) for dogs fed the PM diet. App arent ileal digestibilities of DM, OM, fat, and TDF were not different amon g treatments; however, CP digestibility at the terminal ileum was higher (P < 0.01) for diets containing soy protein sources than for PM. Total tract CP digestibility was greater (P < 0.01) for soy protein-containing diets th an for PM. Apparent total tract digestibilities of DM, OM, fat, and TDF wer e not different among treatments. Apparent amino acid digestibilities at th e terminal ileum, excluding methionine, threonine, alanine, and glyciae, we re higher (P < 0.01) for soy protein-containing diets than for PM. Dogs fed SPC diets had lower (P < 0.01) fecal outputs (g asis feces/g DMI) than dog s fed the SF diet, and dog's fed SBM tended (P < 0.11) to have lower fecal outputs than dogs fed the SF diet. However, dogs fed the PM diet had lower (P < 0.03) fecal outputs than dogs fed SPC-containing diets. Fecal outputs and scores reflected the TDF and nonstructural carbohydrate contents of the soy protein fraction. Soy protein sources are well utilized by the dog pri or to the terminal ileum, and SPC offers a viable alternative to PM as a pr otein source in dry, extruded canine diets.