Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to encourage dogs to mate naturally [title] Keep the female at a healthy weight. [step] Females are more likely to conceive, and have healthy pregnancies, if they stay at a healthy weight. An under or overweight female may have problems conceiving and carrying puppies to term.

Ending1: [title] Expect a 1000s vaccination. [step] The only time it is necessary to vaccinate your dogs is once a year. Ending2: A healthy weight will encourage a healthy pregnancy. [substeps] Talk to your vet about your dog's weight. Ending3: After awhile, it can become clear that your dog is not producing enough sperm to breed a new litter. [substeps] However, you should still take care to keep the female at a healthy weight. Ending4: Doing this is important as an overweight female is more likely to transmit the fetus than the puppy. [substeps] Check with your veterinarian for how much weight she has to lose.

Answer format: ending1/ending2/ending3/ending4