Science News

Sperm Quality Of Dogs Declining Due To Chemicals In The Environment

Photo from Pixabay

A center in England has been breeding, raising and training generations of dogs for physically challenged people over the last few decades, including Labrador retrievers, curly coat retrievers, golden retrievers, Border Collies and German Shepherds.

The furry animals presented scientists at the University of Nottingham with the unique opportunity to study dog fertility in a single location that offered five types of purebred species, uniform conditions, and systematic record-keeping. In 1988, the scientists began an annual test of the male dogs’ sperm, the New York Times reports.

According to the study, there was a decline in sperm quality and other effects believed to have been caused by environmental factors. Over the course of 26 years, sperm motility had dropped by 30% in all five breeds studied. While the decrease has not reached critical levels, as the studs are still able to impregnate females, any further decline could eventually disrupt healthy reproduction.

Richard G. Lea, head researcher and associate professor of reproductive biology at the University of Nottingham’s School of Veterinary Medicine and Science, says,

The dogs who share our homes are exposed to similar contaminants as we are, so the dog is a sentinel for human exposure.

The researchers examined between 42 to 97 studs from 1988 to 2014. From 1994 to 2014, the team noticed that the death rate of female puppies, while small, has increased three times over. Undescended testicles in male pups, also small, had a tenfold increase from 0.1 to 1%.

Upon analyzing testicular tissue for chemical content in dogs that were no longer breeding or had been neutered, researchers found concentrations of chemicals used in electrical transformers and paint, as well as in plastics. Recent, additional analyses of the dogs’ semen showed levels of the same chemicals, including PCBs and diethylhexyl phthalate or DEHP. PCBs have been banned but can remain for a long time in the human or animal body.

Trace amounts of these chemicals were likewise present in the dogs’ food. While the brands were not named, Lea says the dog food, both wet and dry, are marketed worldwide.

According to the study, it was unclear as to how the chemicals got into the food. The researchers suggest that it may have been due to the packaging or the water that had been used in the ingredients.

The researchers could not also determine for sure if the dog food is a direct, or only, source of the chemicals found in the dogs. Lea says it is probably a primary source.

This study may support prior research on the effects of the environment on human semen, the scientists state. For the past 70 years, there has been a decline in human sperm quality, and a rise in testicular cancer cases as well as genital tract problems. The scientific community continues to debate on whether or not this is directly caused by industrial chemicals — such studies tend to be conducted in varying lab conditions, with different standards, making cause-and-effect difficult to prove.

Peter J. Hansen, a professor of reproductive biology at the University of Florida, says he is generally skeptical of studies on sperm quality and chemical exposure. However, he observed, this study from Nottingham found chemicals in both dog tissue and food, and tracked the results over a long period. “I think it was very rigorous,” Hansen says. “It’s much more clear from their data that there was a decline over time, which agrees with the human data but doesn’t suffer from the same research problems.”

One question the researchers had was on whether genetics played a part in sperm quality decline, as purebreds tend to have plenty of health problems stemming from genetic factors. But because the dog center kept excellent, detailed records, inbreeding was ruled out. Undescended testes may have a genetic factor to it, but since it occurred in all five breeds, it must be from something else. Lea says that the declining sperm motility, the most observable effect, does not have strong genetic links.

This study focused on male dogs, so Lea’s team is now looking at ovarian tissue to see if female dogs have similar chemical levels and reproductive problems.

The study was published in Scientific Reports.

Click to comment
To Top

Hi - We Would Love To Keep In Touch

If you liked this article then please consider joing our mailing list to receive the latest news, updates and opportunities from our team.

We don't want an impostor using your email address so please look for an email from us and click the link to confirm your email address.