Hill's Prescription Diet j/d Feline Mobility - 8.5lb Hill's Prescription Diet j/d Feline is clinically proven to help cats be more active in 28 days. Prescription Diet j/d Feline contains omega-3 fatty acids, which nourish cartilage. Controlled phosphorus and high levels of omega-3 fatty acids help maintain kidney health High carnitine helps burn fat while maintaining lean muscle mass