i have a question. i've often read online that it's best to wait to spay/neuter until the dog has fully finished growing, so around a year, 2 for giant breeds. are there any benefits to waiting until then / drawbacks to not waiting? or is it just personal preference?
There’s not really a ‘perfect’ timing, and so much depends on individual situations.
With female dogs, we know that malignant mammary cancers are extremely common in dogs that are left entire, to the extent that approximately 1 in 20 entire female dogs will die from it. If you desex a female dog before her first heat, the odds of her getting this otherwise common cancer is only 1 in 10,000.
Each heat cycle she goes through increases her relative risk. 1 in 1,000 after the first heat, approximately 1 in 100 after the second and so on.
For a small dog without much skeletal growth to do, I aim to desex before the first heat (barring urogenital abnormalities) to minimize this risk, at around 6 months of age.
For a large or giant breed dog, I may consider delaying this. They usually come on heat later anyway, so waiting until 8 or 9 months usually does not increase their risk of mammary cancer.
The reasoning behind delaying desexing until skeletal maturity is that it’s thought to reduce the risk of some rarer cancers, and cruciate disease. If the owner can adequately manage the pregnancy risk associated with an entire female dog, they may weigh up the pros and cons of waiting those additional months.
HOWEVER in breeds notorious for hip dysplasia, or puppies with an abnormal gait, I instead recommend PennHip Xrays at 16-18 weeks of age to determine whether that individual dog has conformation associated with hip dysplasia. If they do, then I recommend to desex and perform a JPS procedure (Juvenile pubic symphysiodesis) then. This vastly reduces their risk of suffering symptoms of hip dysplasia as an adult, but these dogs should never be bred from.
A particularly concerned owner may elect to have their dog undergo two anesthetics instead of one - PennHip Xrays and JPS at 16-18 weeks, and desexing once skeletally mature, though so far in my experience no owners have elected to do so.
For males the timing of desexing is not critical, though my personal preference is not to leave it too many years due to the inevitable ‘sag factor’ of the empty scrotum.