Sustain helps to maintain a healthy gastrointestinal bacterial population. Supports immune function both within the gastrointestinal tract and body wide. Helps with environmental or diet problems by keeping the gastrointestinal function healthy. Sustains comes in sachets can be given at meal times and can add warm water to them. Dosage is the following; under 20kg – 1 small medium breed sachet, 20-40kg – 1 large breed sachet, over 40kg – 2 large breed sachets