Charities are warning of “another fresh hell” for animals in the coming days, fearing millions could suffer and perish in the heatwave.
Experts are calling on the government to crack down on intensive chicken farms that last month let millions of birds be “cooked alive” in the record UK temperatures.
They also want ministers to suspend journeys of chickens and cattle while the extreme weather persists.
And at the same time, badger advocates warned the mammals would suffer cruel, prolonged deaths unless the cull was postponed.
Last month, whistleblowers revealed how little was done on factory farms to protect chickens from the intense heat in industrial sheds that reached up to 45C and left many suffering heat distress, flapping and panting as they died.
Animal-welfare organisations have told ministers that with temperatures set to reach up to 34C in the next 72 hours and heatwaves worsening in future years, the disaster will be repeated without urgent action.
They are calling for new laws on better ventilation, lower stocking densities – fewer birds crammed into the sheds – and the use of hardier slower-growing breeds that cope better with extreme heat to be made compulsory.
Graphic reports from whistleblowers include one who described seeing “an ocean of green, rotting mush” on a farm after last month’s mass disaster.
Legislation requires ventilation to be efficient enough to save chickens from overheating, but apparently is not always enforced.
The letter to environment secretary George Eustice, seen by The Independent, highlights how last year the Met Office warned of climate change causing heat stress in farmed animals.
It tells Mr Eustice: “With no way to escape the heat and lack of oxygen, we believe it is harder to imagine a more horrific death. Given the number of animals involved, the severity of the suffering, and the poor record of the broiler industry to regulate itself, we believe it is crucial that significant, bold legislative changes are prioritised.”
The letter, from the Humane League UK, Open Cages and Animal Equality, asks for an urgent meeting with the minister.
Cordelia Britton, of the Humane League UK, said: "Another heatwave is coming and we risk another fresh hell for animals - if we don’t act now chickens will die again and again.
"It’s a national disgrace.
"We need the Better Chicken Commitment to be made the minimum legal standard, and for existing laws designed to protect animals from high temperatures to be enforced. The government must not shrug its shoulders and wait for the next catastrophe to happen.”
The Better Chicken Commitment (BCC) involves farming breeds of chickens that grow more slowly than most birds on UK factory farms, which are deliberately reared for rapid and unhealthy weight gain.
Welfare experts say fast growth increases body heat production, making the "Frankenchickens" susceptible to heat stress which in turn raises birds’ already heightened blood pressure.
This, together with high body temperatures, causes heart failure, hyperventilation, dizziness, diarrhoea and death.
But the animal-welfare organisations say slower-growing breeds are less susceptible to extreme heat as well as lameness, impaired breathing and organ failure.
In 2005 the government published a guide on heat stress. And thousands of chickens died in a heatwave in 2019, prompting questions over why the sector was unprepared.
Connor Jackson, head of Open Cages, said: “Most of these chickens that were cooked alive were destined for the shelves of supermarkets. But if the UK government were to step in they could help ensure tragedies like this never happen again.”
He said fast-growing “Frankenchickens”, selectively bred to maximise profits, account for nine in 10 of the 1.16 billion chickens reared each year in the UK.
More than 330 companies have signed the BCC, including Greggs and Nestlé.
At the same time, Compassion in World Farming is calling on the government to suspend journeys for farmed animals during the extreme heat unless absolutely necessary.
The heat inside trucks can be unbearable, with animals desperately panting for air— Phil Brook
Phil Brook, of the charity, said: “The heat inside trucks can be unbearable with animals desperately panting for air.
“Long journeys should be suspended and short journeys should only take place if absolutely necessary and at night when it’s cooler. Sufficient water must also always be within reach.”
It’s impossible to ventilate lorries so that temperatures inside remain below 30 degrees as required by law, he said.
The Badger Trust says it is pleading with Natural England to suspend all badger cull licences during the heatwave, warning that animals left in cages before being shot cannot dig for worms due to the hard ground or quench their thirst, so risk dying from dehydration and heat exhaustion.
On live animal journeys, The Independent understands that the Animal and Plant Health Agency (APHA) has texted and written to livestock keepers and animal transporters with guidance on ensuring animals’ welfare in hot weather.
On chickens, a Department for Environment, Food and Rural Affairs spokesperson said: “It is vital the health and welfare of animals are protected, and we are deeply concerned about recent chicken mortalities.
“The APHA is working to support local authorities in investigating what took place and in taking any appropriate further action.”