Sperm quality in dogs has diminished over the past three decades, and this could explain the purported decline in human fertility.
There is a potential link between environmental contaminants and fertility, say scientists who discovered chemicals in some commercially available pet foods that had a detrimental effect on sperm.
Researchers at the University of Nottingham believe that the study could explain the reported, significant decline in human semen quality.
Richard Lea, reader in reproductive biology at the university’s School of Veterinary Medicine and Science, said: “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.
“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.”
Dr Lea and his team collected semen from between 42 and 97 stud dogs every year, over 26 years, at an assistance dog-breeding centre.
Semen samples were analysed to assess the percentage of sperm that appeared normal and which had the expected pattern of motility.
Sperm motility declined by 2.5% per year between 1988 and 1998, and then at a rate of 1.2% per year from 2002 to 2014.
The research, published in the journal, Scientific Reports, also found that male pups fathered by the stud dogs with declining semen quality were more prone to cryptorchidism (the failure of the testes to correctly descend into the scrotum).
Dr Lea said that genetic conditions were not to blame, because the research was carried out over a relatively short period of time. He said that the study “begs the question” whether a similar effect could be observed in human male fertility.
The purported decline in male fertility is a controversial subject, with many criticising the variability of data.
However, Dr Lea said that the University of Nottingham study provided a “unique set of reliable data from a controlled population”.”
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