- 26-year study revealed a decline in quality of dog sperm over 3 decades
- Chemicals in pet foods are believed to have a detrimental effect on sperm
- Previous studies have shown how chemicals can damage human sperm
- Researchers at the University of Nottingham believe that the study could help explain the reported significant decline in human semen quality
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Ellie Zolfagharifard for MailOnline
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Chemicals in the environment are making dogs less fertile, scientists have found.
The discovery provides even more evidence that harmful chemicals in the environment may also be damaging human sperm.
The research comes from a 26-year study of dog sperm has revealed a gradual decline in quality over the past three decades.
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Chemicals in the environment are making dogs less fertile, scientists have found. The discovery provides even more evidence that harmful chemicals in the environment may also be damaging human sperm
WHY ARE SPERM COUNTS FALLING IN MEN?
Up to a fifth of young men find themselves with a low sperm count, which is defined as having fewer than 15 million sperm per millilitre of semen.
And one in six couples now has difficulty conceiving, with a low sperm count or poor sperm quality the cause in about 20 per cent of cases.
From sunscreen to abstinence, and bacon to cycling, studies have shown a myriad of things which lower sperm count.
Factors include narcotics, stress, being overweight, smoking, wearing tight underwear and chemicals in the environment.
A study last year claimed falling sperm counts could be caused by traces of the contraceptive pill in drinking water,
US scientists said the sex hormone oestradiol – the birth control hormone that passes untreated through sewage plants – has an even larger effect on sperm than Bisphenol A or BPA, as it is widely known.
Scientists are linking this to chemicals found in pet food, which were found to have a detrimental effect on sperm in some commercially available pet foods.
Dr Richard Lea, reader in reproductive biology at University of Nottingham, who led the research, said: ‘This is the first time that such a decline in male fertility has been reported in the dog.
‘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 dogs breeding centre.
Semen samples were then analysed to assess the percentage of sperm that appeared normal and had the expected pattern of motility.
Sperm motility declined by 2.5 per cent per year between 1988 and 1998, and then at a rate of 1.2 per cent per year from 2002 to 2014.
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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.
This is a condition in which the testes fail 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.
Up to a fifth of young men find themselves with a low sperm count, which is defined as having fewer than 15 million sperm per millilitre of semen
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 in science with many criticising the variability of data in the studies.
However, Dr Lea said that the University of Nottingham study provided a ‘unique set of reliable data from a controlled population’ which was not affected by factors – such as in laboratory methods, training of laboratory personnel or improved quality control over the years – which could have caused variations to the results.
Professor Allan Pacey, spokesperson for the British Fertility Society (BFS), added: ‘Although there is conflicting evidence to suggest that sperm quality in humans has declined significantly, this study is particularly interesting as the results suggest an increase in problems of the dog’s testicles and a decline in the number of female dogs born over the study period.
‘In addition, concentrations of some environmental chemicals in the dog’s testicles as well as in commercial dog foods were also detected.
‘Indeed, because dogs share the human home, this could suggest that they might be a useful model species to detect possible threats to male reproductive health.
‘From these results alone, we cannot determine any impact these results may have on human public health.
‘This data must therefore be interpreted with caution and used to guide further studies.’
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