The effect of texturized vegetable protein from soy on nutrient digestibility compared to beef in cannulated dogs

Texturized vegetable protein from soy (TVP) is widely used in canned dog fo ods, but its nutritional value remains in doubt. This study compared appare nt prececal and total intestinal digestibility when four canned diets conta ining reciprocal proportions of protein from TVP (0 to 57%) and from beef ( 100 to 43%) were fed to eight cannulated dogs. As dietary TVP increased, th e following linear changes were observed (P < 0.05): prececal and total int estinal protein digestibility decreased slightly from 77 to 71% and 86 to 8 0%, respectively; prececal amino acid digestibility decreased in parallel w ith protein; prececal carbohydrate digestibility decreased markedly from 80 % to 62% and carbohydrate disappearance in the large intestine increased fr om 8 to 22%; prececal sodium digestibility decreased markedly (from 37 to 4 %); and prececal potassium digestibility decreased (from 93 to 85%). Total intestinal digestibility of sodium and potassium decreased little (from 97 to 95% and from 98 to 97%, respectively); fecal mass and water content incr eased markedly (from 98 to 174 g/d and from 61 to 72%, respectively); and f at digestibility was unaffected. Prececal phosphorus digestibility from two diets containing TVP was lower than that from the all-beef diet (13 and 17 %, vs 26%, P < 0.05). In conclusion, TVP is a useful source of protein in c anine canned diets because amino acids from TVP are almost as digestible as those from beef in the canine intestine. Nevertheless, soy carbohydrate is poorly digested and large amounts of TVP inhibit small intestinal electrol yte digestibility and increase fecal water content.