Colchester Zoo in Essex plans to make a �1 donation to Save the Rhinos for every pot of the excrement sold.

A zoo spokeswoman said: "We have four white rhinos which produce up to 20 wheel barrows of poo each day which is then freshly potted ready for sale."

The zoo has an endless supply of the environmentally friendly poo which is a good garden fertiliser, she added.

The rhino excrement looked and smelt very similar to hay, the spokeswoman said.

"Because rhinos are herbivores their faeces' smell's musty, a bit like hay, and isn't as offensive as carnivore faeces," she added.

Poaching and habitat loss has reduced the total world's rhino population from about 70,000, 30 years ago, to less than 18,000, according to the World Conservation Union.

The zoo's campaign will run until September.