Dogs in the UK are less fertile than they were 26 years ago according to a new study and this could reveal some interesting findings about male, human fertility.
Changes in environment are thought to be the main cause of the fertility drop.
The study, led by researchers at The University of Nottingham, has discovered that the fertility of dogs may have suffered a sharp decline over the past three decades.
The research, published in the academic journal Scientific Reports, found that sperm quality in a population of stud dogs studied over a 26-year period had fallen significantly.
The work has highlighted a potential link to environmental contaminants, after they were able to demonstrate that chemicals found in the sperm and testes of adult dogs – and in some commercially available pet foods – had a detrimental effect on sperm function at the concentrations detected.
The Guardian reports:
Richard Lea, of Nottingham University’s school of veterinary medicine and science, and colleagues collected samples of semen from a carefully monitored population of Labradors, Border Collies, German shepherds and Golden Retrievers used as stud to breed dogs intended to help the disabled. They tested 1,925 samples of ejaculate from a total of 232 different dogs at the rate of between 42 and 97 dogs every year.
And they found a drop in sperm motility – the ability to swim in a straight line – of 2.4% per year from 1988 to 1998. Even once some dogs were excluded from the study because their fertility was in some way in question, from 2002 to 2014 the scientists still measured a decline of 1.2% per year.
“Why the dog?” said Dr Lea. “Apart from the fact that it is a great population of animals to work with, dogs live in our homes, they sometimes eat the same food, they are exposed to the same environmental contaminants that we are, so the underlying hypothesis is that the dog is really a type of sentinel for human exposure.”
The decline in canine sperm quality does not, for the moment, augur the end of the dog as a species. “It’s very unlikely” Dr Lea said. “It’s very difficult to say at what point this becomes a problem.”
The researchers saw increases in cryptorchidism in the study dogs’ pups over the years. They also saw a clear connection between environmental chemicals and declining fertility. How this might work, however, is not so clear.
“If you think about it, we are exposed to a cocktail. Who knows how many chemicals are out there and what they are doing? It gets even more complicated when you start to look at the effects of mixtures of chemicals,” Dr Lea said.