Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to promote safe whelping for older dogs [title] Avoid breeding a dog over six years old. [step] Depending on breed, it's best to mate your dog between the ages of two and six. A pregnancy after age six can pose significant health risks to both the mother and pups, even if the mother was in good health before the pregnancy.

Ending1: [substeps] If you expect to bring your dog into a breeding pair, hold onto the dog until age 6 when you will be able to start breeding your dog with hope for success. Avoid breeding your dog shortly after the baby arrives due to the transmission of puppies. Ending2: [substeps] You may want to partner your dogs if you have a twin dog or share a large family. If you do not have a large family, or think it is wise to breed a dog over two years old (to begin with), ask your vet. Ending3: You should also not breed two dogs at the same time until about two to four years of age. Also, after two to three years of age, breeding can cause physical or behavioral problems for both dogs. Ending4: If your dog is pregnant at an older age, you will need to stay in close contact with its vet throughout the pregnancy. [substeps] It's always wise to take your dog to the vet for a pre-breeding exam before mating it, regardless of age.

Answer format: ending1/ending2/ending3/ending4