Spey surgery is a common, routine procedure and there are benefits of speying bitches that are not going to be used for breeding.
Mammary tumours: These tumours are hormone driven and approximately half of these will be aggressive tumours that spread to internal organs and bones. If you spey your dog before her first heat, the incidence of mammary tumours is 0.5%. If she has had more than 1 heat her incidence rises to 8%. If she has had more than 2 heats and is over 2.5 years old, this rises to 40%.
Pyometra: this is a uterine infection and is life threatening in dogs. The most effective way to prevent this is with speying.
Avoiding heats: This saves trips to the vet to suppress heats in your dog and keeps your male dogs mind on their jobs, not on the bitches.
Unwanted pregnancies: Pregnancies take your dog out of work and it is costly to abort puppies, large huntaways typically cost $285.
If you are planning on using your dog for breeding, the optimum time for this is when she is in her younger years i.e. 3-7 years old. Fertility and litter size decrease with age. Puppy deaths increase with age and can be as high as 80% in 8 year old dogs due to age of the bitch.
Contact the clinic if you would like to discuss any of this further.