According to iAfrica, this came after years of battling "inhumane and cruel" practices in the industry, it said.

"The NSPCA has grown and developed since the code was established. Science, technology and awareness of the treatment of animals have evolved in the interim," said spokesperson, Grace De Lange.

The NSPCA had, in the past, offered its "qualified support" for the code even though it disagreed with some of the practices.

CEO of the SA Poultry Association (Sapa), Kevin Lovell, said the association was currently writing up a new code of practice and this would be implemented in the middle of the year.

"We've been speaking to the NSPCA with regards to reviewing the code and it's disappointing that they've decided to withdraw from the process," he said.

"They [NSPCA] offered suggestions and we have adopted some of them... but they still pulled out."

Ms De Lange described the industry's practice of freezing unhatched eggs as "a practice we oppose and which has humane alternatives".

The organisation had also disagreed with cage sizes at chicken farms. "An example is putting laying hens in a cage that is the size of an A4 page. They have to sit there for approximately 350 days," Ms De Lange added.

Mr Lovell confirmed the cage sizes, saying: "The chickens are smaller than an A4 page so they can actually move around."

Ms De Lange also referred to three incidents where live chicks and unhatched eggs were dumped in 2010 and early this year. "There were two dumpings at rubbish dumps in Lichtenberg and Standerton and another dumping at a hatchery in Potchefstroom," she alleged.

Mr Lovell said Sapa was "completely against the dumpings" and but could not confirm if the incidents involved Sapa members.

iAfrica reports that the NSPCA was calling for the code to be re-written by an independent body like the SA Bureau of Standards (SABS) with input from other animal welfare organisations.

Mr Lovell said working with the SABS was "not necessary". He said: "Our [code] is an international best practice model... we already comply with the animal protection act."

The NSPCA said it "works towards humane methods, animal-friendly production and a better life for animals". "We cannot have our name associated in any way with a code or industry that works in the opposite direction to the detriment of animals," Ms De Lange added.