Tag Archives: neutering

Big Dogs Face More Joint Problems if Neutered Early

Heavier mixed-breed dogs have higher health risks if neutered or spayed early, according to a new study from researchers at the University of California, Davis. The study found mixed-breed dogs weighing more than 44 pounds as adults are at higher risk for one or more joint disorders if neutered before 1 year of age. Dogs weighing up to 43 pounds had no increased risk for joint problems. The study was published in the journal Frontiers in Veterinary Science.

It’s standard practice in the U.S. and much of Europe to neuter dogs by 6 months of age. This study, which analyzed 15 years of data from thousands of dogs at UC Davis Veterinary Medical Teaching Hospital, suggests dog owners should consider their options carefully.

“Most dogs are mixed breeds,” said lead author Benjamin Hart, distinguished professor emeritus at the UC Davis School of Veterinary Medicine. “We hope this study will influence the spay or neuter process in order to give people wishing to adopt a puppy the time to make an informed decision on when to spay or neuter.” 

Researchers examined common joint disorders including hip dysplasia, elbow dysplasia and cranial cruciate ligament tears, a knee injury, in five weight categories. They also looked at risks of mixed-breed dogs developing cancers based on weight but found no increased risk in any weight category compared to intact dogs.

The risk of joint disorders for heavier dogs can be up to a few times higher compared to dogs left intact. This was true for large mixed-breed dogs. For example, for female dogs over 43 pounds, the risk jumped from 4 percent for intact dogs to 10-12 percent if spayed before a year of age.

Neutering policies should be reviewed

“The study raises unique challenges,” noted co-author Lynette Hart, professor at the UC Davis School of Veterinary Medicine. “People like to adopt puppies from shelters, but with mixed breeds it may be difficult to determine just how big the dog will become if you don’t know anything about the dog’s parents.”

Neutering prior to adoption is a common requirement or policy of humane societies, animal shelters and breeders. The authors suggested the policy be reviewed and modified appropriately. Shelters, breeders and humane societies should consider adopting a standard of neutering at over a year of age for dogs that will grow into large sizes.

Lynette Hart said the study is especially relevant for people and organizations raising service dogs.

“They need to take a serious look at this,” said Hart. “Joint disorders can shorten a dog’s useful working life and impact its role as a family member.”

A previous study conducted by the UC Davis researchers found health risks based on neuter age varied greatly depending on the breed of the dog.

Source: University of California Davis media statement

When Should You Neuter Your Dog to Avoid Health Risks?

10 year study on neuteringSome dog breeds have higher risk of developing certain cancers and joint disorders if neutered or spayed within their first year of life. Until now, studies had only assessed that risk in a few breeds. A new, 10-year study by researchers at the University of California, Davis, examined 35 dog breeds and found vulnerability from neutering varies greatly depending on the breed. The study was published in the journal Frontiers in Veterinary Science.

“There is a huge disparity among different breeds,” said lead author Benjamin Hart, distinguished professor emeritus at the UC Davis School of Veterinary Medicine. Hart said there is no “one size fits all” when it comes to health risks and the age at which a dog is neutered. “Some breeds developed problems, others didn’t. Some may have developed joint disorders but not cancer or the other way around.”

Researchers analyzed 15 years of data from thousands of dogs examined each year at the UC Davis Veterinary Medical Teaching Hospital to try to understand whether neutering, the age of neutering, or differences in sex when neutered affect certain cancers and joint disorders across breeds. The joint disorders examined include hip dysplasia, cranial cruciate ligament tears and elbow dysplasia. Cancers examined include lymphoma; hemangiosarcoma, or cancer of the blood vessel walls; mast cell tumors; and osteosarcoma, or bone cancer.

In most breeds examined, the risk of developing problems was not affected by age of neutering.

Breed differences by size and sex

Researchers found that vulnerability to joint disorders was related to body size.

“The smaller breeds don’t have these problems, while a majority of the larger breeds tend to have joint disorders,” said co-author Lynette Hart, professor at the UC Davis School of Veterinary Medicine.

One of the surprising exceptions to this was among the two giant breeds — great Danes and Irish wolfhounds — which showed no increased risk to joint disorders when neutered at any age.

Researchers also found the occurrence of cancers in smaller dogs was low, whether neutered or kept intact. In two breeds of smaller dogs, the Boston terrier and the shih tzu, there was a significant increase in cancers with neutering.

Another important finding was that the sex of the dog sometimes made a difference in health risks when neutered. Female Boston terriers neutered at the standard six months of age, for example, had no increased risk of joint disorders or cancers compared with intact dogs, but male Boston terriers neutered before a year of age had significantly increased risks.

Previous studies have found that neutering or spaying female golden retrievers at any age increases the risk of one or more of the cancers from 5 percent to up to 15 percent.

Discuss choices with veterinarians

Dog owners in the United States are overwhelmingly choosing to neuter their dogs, in large part to prevent pet overpopulation, euthanasia or reduce shelter intake. In the U.S., surgical neutering is usually carried out by six months of age.

This study suggests that dog owners should carefully consider when and if they should have their dog neutered.

“We think it’s the decision of the pet owner, in consultation with their veterinarian, not society’s expectations that should dictate when to neuter,” said Benjamin Hart. “This is a paradigm shift for the most commonly performed operation in veterinary practice.”

The study lays out guidelines for pet owners and veterinarians for each of 35 breeds to assist in making a neutering decision. Read the full list here.

Source:  UC Davis

Do sterilized dogs live longer?

New research from the University of Georgia suggests that neutering procedures could add to the length of a dog’s life and alter the risk of specific causes of death.

Looking at a sample of 40,139 death records from the Veterinary Medical Database from 1984-2004, researchers determined the average age at death for intact dogs—dogs that had not been spayed or neutered—was 7.9 years versus 9.4 years for sterilized dogs.

These figures may seem low considering how many pets live much longer, but the researchers noted that the life spans would be lower than those seen more widely because their sample was taken from dogs seen at teaching hospitals (so other things would have been going on and the study population would have had more sick animals).

The researchers stand behind their results – that the difference between neutered and intact is real.

Dr. Kate Creevy, an assistant professor of internal medicine at the College of Veterinary Medicine. “The question that raises is why would you die younger if you have offspring?”

For the first time, researchers have been able to measure costs of reproduction in terms of the actual causes of death, finding that the causes of death differed between sterilized and intact dogs. Dogs who had undergone a gonadectomy (a spay or castration) were more likely to die from cancer or autoimmune diseases. Those in the sample who still had functional reproduction systems at death were more likely to die from infectious disease and trauma.

“Intact dogs are still dying from cancer; it is just a more common cause of death for those that are sterilized,” said Jessica Hoffman, a UGA doctoral candidate in the Franklin College of Arts of Sciences who co-authored the study.

Some of the reproductive hormones, particularly progesterone and testosterone, she said, could suppress the immune system, explaining why there is an increased risk of infection among dogs that have been sterilized.

The full journal article, published in PLoS One, can be viewed here.

Source:  University of Georgia media statement

Pet obesity at the molecular level

A University of Illinois research team led by Professor Kelly Swanson has published research which describes how nutrients and biological compounds in foods can affect gene expression in animals.

The research will help to understand the underlying reasons for obesity in pets.  Professor Swanson explains that obesity has its roots in the domestication of dogs.  Because dogs no longer hunt or compete for their food and are speyed or neutered (so not having to mate),  the typical dog has much smaller energy requirements than its forefathers.

The research team explains that when more energy (food) is consumed than is required, it is stored as fat in the adipose tissue (fat tissue).  Adipose tissue secretes more than 50 substances known as adipokines, which are cell-signaling molecules that are involved in metabolism, immunity and inflammation.

In obese dogs, levels of the adipokine leptin increases while the levels of the  adipokine adiponectin decreases.

The researchers aim to study obesity at the molecular level, so they can help to prevent it happening.

Source:  University of Illinois media statement