As per the Health Warranty and Purchase Agreement, the dog must be spayed or neutered by nine months of age.
My Veterinarian has the best saying, "You need to weigh the options that are best for you and deciding what is best for you and your dog." I can't think of a reason why I would not neuter at male dog at 9 months old if I was keeping it as a perfect pet. Below are my reasons why I would neuter by 9 months old.
At 7 months old the dogs is as tall as it is going to be; so the dogs has it hormones levels during the heavy bone growth stage.
At 7-8 months the male dogs will learn to lift his leg to pee; during his adolescent hormone stage. If you neuter before he learns to lift his leg he will squat to pee the rest of his life. If you neuter after he learns to lift his leg then it is a habit and he will continue to pee on things to mark his territory; furniture, bushes, etc.
At 7-8 months the male dogs during his adolescent hormone stage he will start to sniff out female dogs in heat which dogs can smell several miles away, thus you risk the male dog running off after the scent and being injured or lost, hit by a car, etc.
Females can go in heat at 8 months old and about a month before they go in heat they get uncontrollable. You will think you will never be able to train her. thus, many people give up and re-home their dogs and you find many females young adult dogs in Shelters.
We do not participate in Early Spay and Neuter procedures done at 8 weeks old on our puppies, because our experiences has been that it sets the pups’ weight gain back a week, which is not good during this rapid growth period. Keeping the puppies’ nutrition level up is a huge concern of ours, and we do not feel that young puppies have sufficient body weight to sustain lower levels of food consumption following the procedure. That being said, the research on early spaying and neutering has been inconclusive, so discuss the options with your vet and make the decision with which you’re most comfortable. Research shows puppies that were spayed or neutered early age have offset bone growth. Some have longer weaker legs than their breed standard. Showing us that the dogs need their hormones for strong bone growth during their first 7 months.
To recap: There are countless studies out there back to 1950 that say the best age to spay a dog is six months, time and time again through the ages 6 months has come up more often. Many say 7-9 months; as a dog's bones are finished growing at 7 months old and then they pack on a little more fat and muscle. Thus, going for the 7 month mark the dogs' have their hormones for bone growth. There are a few studies showing wait for the first heat cycle. Why the different results in studies? Because, Grant Money is provided for studies; ever study can not come up with the same result or it would look like someone embezzled the money and didn't do a study or why do new studies to only come up with the same results. Do what is safest for the dog and the safest would be for the female dog to not accidently get pregnant. Oh yes, people think it is cute to have a litter of puppies. When I was young our little poodle got pregnant ,which we lived in a neighborhood and didn't know which dog was the father. She died giving birth, a big puppy was stuck in her. A lot of knowledge and learning goes into having a healthy litter of puppies. I have heard from a novice breeder that they lost an entire litter of newborn puppies to hyperthermia and they had studied and read a lot on having a litter of puppies and had had 3 previous litters. To purchase the correct equipment to successfully have a litter of healthy puppies takes for more money than one litter of puppies, so why go through the risk. You say you have a fenced back yard, lol, any horny male could scale a fence. When a female dog accidently gets pregnant you will not know it until about 2-3 weeks prior to delivery when she starts showing signs of being pregnant, so you do not know the due date. Is someone going to stay with the dog 24/7 to help her go through delivery? No taking a shower or running to the grocery store, because that is when they are going to go in labor.
S0 aim to spay or neuter at 7 months old and make sure it is done by 9 months old is the best advice I can give you.