Hills Prescription Diet Gastrointestinal Biome Cat Food with ChickenHill's PRESCRIPTION DIET Gastrointestinal Biome Cat Food with Chicken Hills nutritionists and veterinarians formulated Prescription Diet Gastrointestinal Biome nutrition with ActivBiome+, a proprietary ingredient technology, clinically shown to promote regular healthy stool in as little as 24 hours and help reduce risk of recurrence. How it works: Proprietary ActivBiome+ technology nourishes your pet's microbiome Unique blend of prebiotic fibres