Two sealed cardboard boxes rammed full of hens were left without air holes outside an animal rescue centre.
Seven of the 30 hens were found dead, the rest almost dead, squashed together in sweltering heat.
Irene Clarke, who runs The Old Gardens Animal Rescue Centre in Sidlesham, near Chichester, said: ‘My 13-year-old daughter was with me when we found them, it broke her heart when she opened the boxes.
‘They were left outside the centre in two TV boxes, big enough for three hens not 15.
‘They had no air to breath, they were rammed top of each other in such a state.’
Irene and her young daughter wrapped the barely alive chickens in cold wet towels and, though seven were already dead, they fortunately managed to revive the rest who are now being nursed back to health.
Irene said she had earlier taken a call from a man who said he had 30 hens to drop off at around 4pm on Tuesday, August 15.
She told him she wasn’t at the centre and the latest he could bring them was 5.30pm, but to ring first.
She said: ‘There was no call but luckily we decided to come back at about 5.10pm. We found them stuffed in the boxes, it was so hot, he could have cut air holes at least.
‘It was heartless. He obviously bred them because there was young ones in there.’
Irene said the rescue centre is currently ‘completely overrun’ with animals after she rescued 100 ‘lovely white ducks’ and another 200 hens set for slaughter at local battery farms.
Irene said the birds would come back into lay again and anyone interested in taking some for domestic use should get in touch.
The centre relies on donations and anyone who can help should ring Irene on 0777 567 0819.