A major fertility survey being carried out by researchers in Edinburgh will see 1,000 young Scots men agreeing to send sending samples of their sperm through the post.

The study - which is receiving almost £500,000 pounds from the government - begins next week and follows fears that western sperm counts are falling.

Scottish men, aged between 20 and 30, who have been selected at random from National Health Service lists, will provide samples at home.

Scientists will give the men specially developed liquid - which will keep the sperm alive for 48 hours - to mix with their samples.

They will then use special packs to post the sperm to the Medical Research Council's reproductive biology unit in Edinburgh.

Dr Stewart Irvine, head of the research project, said the postal method had been chosen in order to gain a nationwide census of men's sperm.

He said: "We can ask people to come into the unit and give a sample but then you will generally only get men from the Edinburgh area and we wanted a truly national survey.

"Normally you would have to analyse the sperm within 60 minutes of it being given but with the preservative chemical we are sending out in the packs the sperm will be kept alive for 48 hours so that gives us time to receive it and analyse it.

"It is the first time a study has been done like this and I am really pleased with the response so far from the men selected."

They were initially sent out a detailed health and lifestyle questionnaire.

In addition their mothers were asked to provide details about her lifestyle when she was carrying the child and during his early years.

Dr Irvine said: "The General Register Office for Scotland pulled up about 10,000 names for us from NHS lists and with the help of GPs we constructed a mailing list and asked if they wanted to participate.

Good response needed

"We then sent out the questionnaires and will this week send out the first batch of the special packs for samples to those who responded.

"For a meaningful result we need to get about 1,000 responses and I am confident we will get that.

"We will then examine the sperm at body temperature and see what percentage are motile - that is swimming around - or not."

Dr Irvine said the team were keen to identify any factors which may be affecting sperm quality.

He added: "What we want to find out is where we are in terms of sperm quality today because there are a lot of fears about whether it is getting worse.

"We also want to look at the true relationship between health and lifestyle issues and see what sort of thing affects the quality."

The results of the study should be published by the end of this year.