Hill’s Prescription Diet z/d Low Fat a hydrolyzed soy formula, low fat nutrition that will help avoid adverse food reaction, reducing dermatologic and gastrointestinal signs from food sensitivities and start to help manage gastrointestinal signs in dogs with chronic gastrointestinal issues z/d Low Fat is unique in that it contains a hydrolyzed soy formula, is easily digestible, contains a low fat formula comparable to Hill’s Prescription Diet i/d Low Fat, includes our proprietary blend of prebiotic fibers called ActivBiome+ to activate the pet’s gut microbiome for optimal stool quality, is urinary friendly with the S+OXSHIELD, and has no animal protein.