Chemicals Causing Fertility Problems in Dogs, Study Says

(CN) — The chemicals humans spew into the environment is likely the reason the sperm count of dogs has declined over the past three decades — and may be why human fertility has declined as well — a recent study finds.

Scientists at the University of Nottingham researched infertility in dogs, concluding that environmental causes have led to a 30 percent sperm count reduction in the five breeds of dogs examined.

The findings may provide another piece of the puzzle over the decline in human sperm quality as well, which has sparked debate among scientists.

"This is the first time that such a decline in male fertility has been reported in the dog and we believe this is due to environmental contaminants, some of which we have detected in dog food and in the sperm and testes of the animals themselves," study leader Richard Lea said.

The researchers collected samples from stud dogs at an assistance dogs breeding center over the past 26 years. Gary England, who oversaw the collection of semen, said that study's findings are particularly useful due to the samples being processed and analyzed at the same laboratory, using the same protocols each time.

The study focused on five specific breeds of dogs — golden retriever, Labrador retriever, curly coat retriever, German shepherd and border collie. The team analyzed 42 to 97 dogs each year.

Lea's team collected and analyzed the dogs' sperm, which actively swam and seemed normal under a microscope.

However, the researchers also discovered a significant decrease in the percentage of free-swimming sperm over the past 26 years, declining 2.5 percent annually between 1988 and 1998, and 1.2 percent each year between 2002 and 2014.

The team also found that the male pups — generated from the stud dogs with declining semen quality — had an increased likelihood of develop cryptorchidism, a condition that prevents the proper lowering of the testes of pups into the scrotum.

Sperm collected from the same breeding population of dogs, and testes recovered from dogs undergoing routine castration, were found to have environmental contaminants at levels that disrupt sperm movement and viability when tested. The chemicals found to disrupt sperm quality were also discovered in a variety of commercially available dog foods, including formulas and brands specifically marketed for puppies.

"We looked at other factors which may also play a part; for example, some genetic conditions do have an impact on fertility. However, we discounted that because 26 years is simply too rapid a decline to be associated with a genetic problem," Lea said.

Studies over the past 70 years have suggested a drastic decline in human semen quality, as well as a series of issues called testicular dysgenesis syndrome, which impact male fertility and increase the risks of testicular cancer and testes that don't descend normally.

"The Nottingham study presents a unique set of reliable data from a controlled population which is free from these factors. This raises the tantalizing prospect that the decline in canine semen quality has an environmental cause and begs the question whether a similar effect could also be observed in human male fertility," Lea said

He added, ""While further research is needed to conclusively demonstrate a link, the dog may indeed be a sentinel for humans - it shares the same environment, exhibits the same range of diseases, many with the same frequency and responds in a similar way to therapies."

The team's findings were published in the journal Scientific Reports.

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