In our contract, males are not to be neutered before 24 months of age and females are not to be spayed before 18 months of age. Early neutering was associated with an increase in the occurrence of hip dysplasia, cranial cruciate ligament tear and lymphosarcoma in males and of cranial cruciate ligament tear in females. Findings of this study were consistent with earlier studies, suggesting similar increases in disease risks. Please read up on the effects of early spay/neutering to understand why we require our dogs to stay intact until they are fully grown.
For peer reviewed data, you can check out these links:
We like this article that we feel sums it all up nicely: https://dogsfirst.ie/health-issues/dog-neutering/
Here are a few other links: