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.  Dr Lea said the slowing decline in recent years could be a result of environmental controls which have seen some of the hormone disrupting chemicals banned.

The research, published in the journal Scientific Reports, also found that male pups fathered by the dogs with declining semen quality were more prone to cryptorchidism - a condition in which the testes fail to correctly descend into the scrotum.

Experts said it was important to move to human studies to see if a chemical link could be responsible for male infertility.

Prof Darren Griffin, Professor of Genetics, University of Kent, said: “The association with environmental chemicals, while not causal at this stage is certainly one to put on the watch list.

“The study certainly paves the way for human studies of a similar type and for experimental studies of model systems on the effects of these chemicals.”

Professor Allan Pacey, spokesperson for the British Fertility Society (BFS), said: “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.”

Gudrun Ravetz, Junior Vice President, British Veterinary Association, said the BVA supported further research to identify if environmental causes were having a significant impact on dog fertility.

Source : www.telegraph.co.uk/

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