Experienced and professional animal trainer provide their insights in answering this question :
A. Pros: Neutering may decrease bad behaviors like aggression and roaming, decrease/eliminate chances of certain cancers, and help eliminate the chances of an accidental litter.

Cons: It may not completely eliminate sex related behaviors, especially the longer you wait, and you won’t be able to breed him.

On the other hand, I would only breed him if you plan on thoroughly researching the breed and investing in proper veterinary care. Breeding, when done right, is not a lucrative hobby.

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Neutered pets are also easier to get along with. They tend to more gentle and affectionate. Neutered males tend to roam less and typically are not involved in as many fights with other animals. Neutering keeps your dog healthier.
Neutering prevents unwanted pregnancies, pregnancy related illness and has many other health benefits. Most dogs can be neutered from 4-6 months old, but it`s important to speak to your vet about the right time to neuter your dog. PDSA vets recommend that all dogs are neutered unless your vet advises against it.
An age of six to nine months of age may be appropriate for neutering or spaying a toy breed puppy or small breed puppy but a larger or giant breed may need to wait until they are near or over 12-18 months of age.
But if your dog is healthy, there is no specific age limit to having the procedure done.
Benefits of Neutering (males):

Reduces or eliminates risk of spraying and marking. Less desire to roam, therefore less likely to be injured in fights or auto accidents. Risk of testicular cancer is eliminated, and decreases incidence of prostate disease.

If your dog`s hyperactive behaviour is also down to hormones, then neutering should help. A lot of owners find their dog chills out more after being neutered whether they`re male or female. While neutering your dog might help to calm them down a bit, sometimes that`s not the only cause of a dog being a bit much.
In addition, getting your dog neutered will have minimal impacts on their behavior and personality. It won`t make them any less lively or playful. The only potential effect on their behavior is in fact positive – neutering may help to stop unwanted behaviors such as aggression and urine marking in the house.
Animal specialists say that if you do not neuter your male pets, their testosterone levels will keep rising. When this happens, aggression usually takes over and this can be dangerous. Intact male pets will start fights with other male pets. People can take the brunt of this aggression as well.
Small dogs do not have as many orthopedic issues, therefore it is fine to neuter them on the younger side at 6-12 months of age. For large dogs that are very prone to orthopedic injury/diseases we now recommend waiting to neuter until 9-18 months of age.
On average, it takes about two to four weeks for testosterone levels to decrease significantly after neutering. However, it can take up to six months for testosterone levels to fully decrease.
Any dog that will be over 45 pounds as an adult should be neutered after their growth stops. This time period is typically between 9 and 15 months of age. For females, the decision to spay is based on additional factors. Some of these factors include your dog`s disease risk as well as your and your dog`s lifestyle.
While castration does not calm dogs down, it can reduce testosterone-driven actions such as mounting behaviour. It may increase a dog`s focus or concentration.
In dogs, an incision is made in front of the scrotum, and both testicles are pushed through this single incision and removed. One incision is made over each testicle in the scrotum in cats, so the cat and dog incision areas look different.
Many pet owners find their dogs and cats to be more affectionate after they are spayed or neutered. As a pet owner, you stand to benefit in many ways by spaying/neutering your dog or cat. Dogs and cats that have been spayed or neutered are generally happier.
Following a general anesthetic, some dogs cry and whimper quite loudly. Neutered dogs usually feel some degree of discomfort immediately following their procedure. It is not unusual for your dog to whine or whimper after being neutered, although some dogs can tolerate pain more than others.
Male dogs that are not neutered can develop a prostate enlargement that can ultimately cause difficulty with urinations and bowel movements. They can also develop infections of the prostate. Other medical conditions that can occur are testicular cancer and tumors around the anal area that require surgery.
Although surgical neutering is considered part of responsible pet ownership in the UK (similar to vaccinations) and performed routinely across the country, in Germany and Scandinavia, for example, surgical neutering is considered “mutilation” and is prohibited by law.
The traditional age for neutering is six to nine months. However, puppies as young as eight weeks can be neutered as long as there aren`t other health problems. An adult dog can be neutered at any time but there is a larger risk of complications.
Dogs neutered before puberty don`t experience this rise in hormones and their long bones particularly continue to grow for a longer time resulting in greater height when growth does cease than their un-neutered counterparts.
When you spay or neuter a dog, you are removing organs that produce hormones. If done early in life, the procedure can affect how your dog`s body works and grows. A UC Davis study on 759 Golden Retrievers found: Males neutered before one year old had double the chance of having hip dysplasia.
So yes, you can neuter an older dog—with a happy and healthy outcome!
Age is not a disease, and your dog is never “too old” to receive the quality care he or she needs, even if it requires anesthesia and surgery.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. Is neutering a good idea? What are the main aspects to consider?
ANSWER : A. Neutering is a procedure that surgically removes a dog’s testicles for the purpose of canine population control, certain medical health benefits, and behavioral modification.

There are several pros and cons to neutering. The positive aspects of neutering include the following:
1. Reduces the risk of prostate disorders, including prostate infections, prostate cysts, or enlarged prostate tissue. It also reduces the risk of testicular cancer, perineal hernias, and perianal fistulas.
2. Reduces the risk of dominance and aggression in many dogs due to a reduction in the amount of circulating testosterone.
3. Reduces the occurrence of sexual behaviors, such as humping, urine marking, or licking of genital regions.
4. Population control – neutering prevents dogs from creating more litters of puppies that need homes.

The following are possible issues to consider:
1. Neutering is a surgery that requires general anesthesia causing slight risks involved in placing an animal under sedation and anesthesia. Performing bloodwork prior to any anesthetic procedure can help decrease the risk of complications prior to surgery.
2. There is an increased risk of neutered dogs becoming prone to obesity because of a change in hormones and activity level.
3. Neutering your dog at too early of an age can have complications.

Overall, neutering is a good idea for your dog in order to prevent population overgrowth and specific medical issues that can result if your dog remains intact. Consult with your veterinarian on the details of surgery and any risk factors based on your dog’s age and breed.

The AVMA supports the concept of pediatric spay/neuter in dogs and cats in an effort to reduce the number of unwanted animals of these species. Just as for other veterinary medical and surgical procedures, veterinarians should use their best medical judgment in deciding at what age spay/neuter should be performed on individual animals.

Read Full Q/A … : Spay/Neuter Your Pet

Q. Hi, what are the pros and cons of neutering?
ANSWER : A. Pros: Neutering may decrease bad behaviors like aggression and roaming, decrease/eliminate chances of certain cancers, and help eliminate the chances of an accidental litter.

Cons: It may not completely eliminate sex related behaviors, especially the longer you wait, and you won’t be able to breed him.

On the other hand, I would only breed him if you plan on thoroughly researching the breed and investing in proper veterinary care. Breeding, when done right, is not a lucrative hobby.

Q. To neuter or not to neuter?
ANSWER : A. If you are not going to breed from your pet then definitely neuter. It removes unwanted sexual behavior as well as limits diseases that your pet may suffer from if not neutered.

Q. We can I go to get my cats fix for free
ANSWER : A. It depends where you live. Some animal charities may give out neutering vouchers for either free or low cost neutering but you will have to phone around. Just remember pets are a luxury to own and if you can’t afford the basics such as neutering, insurance, vaccines and monthly flea treatments then you shouldn’t even consider owning a pet.

Q. Hi. Our dog that we rescued and have had for a few months now pees when he’s nervous. We don’t acknowledge it but it’s very frustrating.
ANSWER : A. How old is he? Is he neutered? Any recent changes in the household? In what situations does he urinate? I would take him to see a vet to rule out any medical causes, such as a UTI, kidney disease, or prostate disease. If all is well I would make sure he is neutered. Lastly, if it is behavioral, he may grow out of it. I would make sure you are not scolding him when he does it, and continue positively reinforcing appropriate urination. Other than that, we need to know a little bit more about the situations in which he does it to possibly modify behavior.

Q. I have been told that if I don’t have my toy Poodle neutered, he can get testicle cancer. Is this true? Is surgery-free neutering with Zeuterin safe?
ANSWER : A. Tumors of testicles in dogs are uncommon. The problem we face in older, not castrated dogs is prostatic diseases. Dogs can develop prostate enlargement, infection, abscess or tumors which we don’t see in castrated dogs. I would recommend surgical neutering rather than hormonal therapy – it is much safer and in long term much cheaper option.

Q. My dog was neutered 6 months ago, but he still humps pillows till full climax. Is this normal?
ANSWER : A. Humping behavior in dogs can be a non-sexual behaviorally related issue in addition to a sexual reproductive one. If your dog was neutered 6 months prior, it is likely that the hormones in his body have reduced already and are not the cause of his behavior. HOWEVER dogs that have previously been bred or had sexual activity prior to neutering may still exhibit interest in and sexual behavior toward in-heat females.

In most cases, the humping behavior is not sexually related and can actually be a sign of “dominance” in dogs. While this term is largely outdated in behavior, it is one that is done usually on one dog to another to show “hey I’m the boss, i wanna be in charge”. Dogs can sometimes take turns doing various similar behaviors during play, or one dog may want to take charge and only allow him or herself to do it. (Yes females can do this too!). If your dog is humping a pillow or toys, he may just be trying to tell his toys he’s the boss! If you feel uncomfortable with this behavior, then stopping him in the act and distracting him with a different game is best.

Q. What would be a good sign for me to get my dog neutered
ANSWER : A. There are no specific signs, the largest benefits for neutering are for long term health gains and neutering early (4-6months) maximizes the gains in this regard and the prevention of pups, neutering before puberty therefore is recommended