In general, it will be between 7-9 months for the smaller females and later for the bigger breeds. Hence, for small dogs, up to an adult body weight of 20kg, we recommend desexing at 6 months old. For larger dogs, we recommend leaving it a little while longer, so about 8-9 months.
There are some old wives' tales that a dog should go through at least 1 heat cycle before she's spayed. This just isn't the case. Studies have shown that the risks of mammary cancer and urinary incontinence are higher if you wait to spay your dog after she's gone through 1 or more heat cycles.
To be clear, the question here is whether or not to spay early or after the first heat cycle. Because of significant risks of pyometra (uterine infection) or mammary cancer late in life we recommend that all female dogs not intended for breeding be spayed before their second heat cycle.
Spaying your dog too early can result in health problems later on since her hormones should have some time to work. Early spaying can increase the risk of hip dysplasia, torn ligaments, bone cancer, and urinary incontinence.
On average, puberty (or sexual maturity) is reached at about six months of age, but this can vary by breed. Smaller breeds tend to have their first estrous cycle at an earlier age, while large and giant breeds may not come into heat for the first time until they reach eighteen months to two years of age.
The typical heat cycle will last between two and four weeks. Your dog or puppy will be fertile during this entire time but there is a small period, 9-10 days into the cycle, where they are especially fertile.
However, spaying does not change your dog's personality. She will not be any less hyper or aggressive after spay surgery if those are her normal personality traits. Spaying will simply calm the aggressive and hyperactive behaviors associated with them being in heat.
A University of Georgia study, based on the medical records of more than 70,000 animal patients, found that the life expectancy of neutered male dogs was 13.8% longer and that of spayed female dogs was 26.3% longer.
Spaying your dog reduces any aggressive behavior patterns so your dog will likely be less aggressive toward people and other dogs after spay surgery.
Heat usually lasts between 2-4 weeks. Early in the cycle, a female dog may not be receptive to male dogs, although some are receptive through the entire cycle. It can be shorter or longer and you'll know the cycle is over when all her vulva returns to its normal size and there's no more bleeding or discharge.
In general, in small breed dogs (less than 50 pounds) we recommend spaying around 6 months. In large breed dogs (greater than 50 pounds) we recommend waiting until after skeletal maturity but before the second heat cycle(usually 12-15 months) in spaying female dogs or anytime after skeletal maturity in male dogs.
The night before the procedure
Give your pet their food around 8 pm and then DO NOT give ANY food to your pet after 9pm. (This includes treats and milk). Water may be left down overnight, but should be removed first thing in the morning.
They can get an uterine infection, called pyometra, that requires emergency surgery. If this condition is untreated or surgery is not done as soon as possible, the infection gets into the bloodstream and becomes fatal. Female dogs that aren't spayed can also get mammary tumors.
Your pet needs to be kept in an indoor crate/ kennel for most of the day and night for the next 10 days. The time of highest risk for the sutures breaking down is 3-5 days after surgery.
The short answer is that no, your dog isn't likely to be less hyperactive after getting spayed or neutered. It won't change their personality much, if at all.
Even though your dog will bleed, she isn't in pain during heat. However, being in heat can make your dog uncomfortable and fidgety. If her symptoms seem to be causing her pain, consult your vet.
Female dogs will often go into heat once every six months (or about twice a year), but the breed size of the dog also affects the frequency of the cycle: a smaller dog may go into heat more often than a larger dog, and a dog's heat cycles may seem irregular when they first start to experience them.
The cycle often happens twice per year. The American Kennel Club (AKC) writes that some smaller breeds can go into heat up to four times per year, and extra-large dogs, such as St. Bernards or Great Danes, may only experience it every eighteen months.
Since the female dog heat cycle bears symptoms comparable to a woman's menstrual cycle in many ways, it is possible to conclude that during your dog's heat cycle she is uncomfortable and maybe even experiences cramping and mild amounts of pain.