The kittens were divided into three groups:
- Group 1 (11 kittens) were neutered or spayed at 7 weeks of age.
- Group 2 (11 kittens) were neutered or spayed at 7 months.
- Group 3 (the control group of 9 kittens) were not neutered until maturity and after the completion of the first phase of the study at 12 months.
The investigators reported that the surgical procedures in the Group 1 kittens were straightforward and uncomplicated, and that the kittens recovered even more rapidly than the Group 2 kittens and Group 3 cats.
