Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to feed your senior dog a healthy diet [title] Determine when to begin a senior diet. [step] Consider your dog as an individual when deciding if it might be time to switch to a senior diet. Different dogs may benefit from senior diets at different ages.

Ending1: Ask yourself this before deciding on a senior diet : [substeps] Senior dog diets vary based on age and breed. For example, many senior diets seek older, juvenile food than older, growing ones, as these age-specific diets expect senior to sleep longer and can give your dog protein sources. Ending2: A healthy dog would be between eight and eighteen pounds (2.1-2.7 kg per kilogram) and a senior dog nine to nine pounds (2.7 to 5.1 kg per kilogram). [substeps] Younger dogs may benefit from senior diets at around eight months of age. Ending3: Additionally, there is no formal definition for what constitutes a senior diet, so these diets will vary by manufacturer. Generally, a senior diet will have altered protein content, lower phosphorus, and reduced caloric content. Ending4: Your second dog might benefit from a senior diet, but senior diets can be beneficial for your dog. [substeps] If your senior dog likes to be on its feet and can't sit down for regular meals in the evenings, it may benefit from a senior diet.

Answer format: ending1/ending2/ending3/ending4