I enclose an interesting article published on the website of Affinity explaining the problem of Alzheimer's disease in dogs . Every time we go more aware of the needs of older dogs have 6-7 years . A dog maxi , over 30kg of weight, is considered senior to 6 years . A dog of medium size ( 10-30 kg) is considered senior 7+ years and a dog -sized Mini after eight years. So this means that for more than half of his life must eat a special food needs or to prevent possible diseases , such as heart problems , kidney , view, joints , neural . It is therefore advisable for senior feed variety , adaptable to the weight of the dog.