Paul has confessed he is embarrassed when visitors see the state of his sheep - because they live to be so old on his farm.The vegetarian musician keeps a flock at his property, but as he refuses to send them to an abattoir they are there until they die of old age,
In an interview for Radio 4's The Food Programme to be broadcast on Sunday, he points out that few people ever see elderly sheep and are surprised by their appearance.
"I live on a sheep farm so we shear the sheep, but they die of old age - and you know what, it's kind of embarrassing, because none of the other farms have got old sheep," he said.
"They're all gone before they're old - they just die like we do. It's life, it's death, it's what happens.
"We just give them a good life and I take the wool from them. but it can be embarrassing. you know, people say 'look at the state of your sheep' and I say yes they're very old and you know there is only one alternative - send them to the knacker's."
In an interview with presenter Sheila Dillon, Paul talks about his vegetarian lifestyle and his desire to encourage more people to try eating less meat. It comes as his late wife Linda's veggie food range is given a new push, with a TV ad campaign and new products. The ex-Beatle is also publicising the idea of taking a break from animal products with "meat-free Mondays".
In the programme, to be broadcast on Sunday at 12.30pm, he explains: "Basically what we're saying with the meat-free Monday campaign is that out of your seven days, you might think of one day being meat-free. we're not really pushing it too heavily. we're not saying you should go veggie, it's good for you.
"We're saying 'just try one day', and a lot of people say that's very do-able, a very accessible idea, and they enjoy it.
"There's all sorts of economic arguments that in a recession, meat tends to be the expensive bit of what you buy, so generally speaking, I think it's a good idea."
Sheila Dillon with an exclusive food interview with Paul. More than thirty years since becoming a vegetarian he reflects on his life through food.
He describes his early life in the terraced council house, 20 Forthlin Road, now owned by the National Trust and where the McCartney kitchen, circa 1955, has been restored. Paul recalls meals of pork chops, liver and tongue , the latter proving to be one of the biggest food challenges of his childhood.
He recounts stories on the road with The Beatles and seeing huge steaks drooping over the plate on their American tour, and then the 1960 trip to India and facing a strict vegetarian diet. Several years later, after spending time on his farm, and influenced by his wife Linda, he stopped eating meat.
So how, from a personal decision based on compassion for animals, did he decide to shift to a more political and campaigning stance on food and farming? Sheila Dillon finds out how he took a fame based on the stage, into arenas like the European Parliament and The White House.