Feline Neuter:

Can be performed any time after 4 months of age. Around 6-7 months of age, undesirable behaviors like spraying can develop.

Feline Spay:

Can be performed any time after 4 months of age. Cats can go into heat as early as 6-7 months and can get pregnant if exposed to an intact male cat.

Canine Neuter:

Small and medium sized dogs: Neutering can be performed as soon as adult canine teeth have erupted, around 6-7 months of age. Around 8-9 months, puppies can develop undesirable behaviors like marking, humping and territorial aggression, and should be neutered to curb those behaviors if they are present.

Large dogs or athletic/working dogs: There is likely a benefit to waiting until large dogs are skeletally mature before neutering. The age of this depends on the size of the dog, but usually about 12 months for dogs. If undesirable behaviors like marking or humping develop, dogs should be neutered to curb these behaviors before they become a habit.

Canine Spay:

Small and medium sized dogs: Spay should be performed at about 6-7 months of age, before their first heat cycle to decrease the risk of pyometra (a deadly uterine infection) and developing mammary tumors later in life.

Large dogs or athletic/working dogs: For larger dogs, there may be a benefit to waiting until 2 months after the first heat cycle until they are skeletally mature to spay. This will increase the risk of mammary cancer (breast cancer) later in life. Heat cycles will involve dogs bleeding for about 2 weeks and dogs will have to be kept away from intact male dogs. Many people elect to spay their large dogs around 6-7 months so they do not have to go through a heat cycle.