By Amitabha Bhattasali
BBC News, Calcutta
A leading animal rights group in the Indian state of West Bengal has released film clips which it says shows the appalling state of poultry farming.
Footage taken by the People for the Ethical Treatment of Animals [Peta] shows crowded, filthy and unhygienic conditions in chicken farms.
They say that their film shows that the conditions the chicken are kept in has led to the spread of the H5N1 virus.
Peta volunteers say the evidence has been compiled over a five year period.
Poultry farmers have denied the group's conclusions and criticised the report as "erroneous".
"These birds are crammed by the tens of thousands into dark, filthy sheds. They can't even move their wings. The chickens' accumulated waste actually burns their eyes," Peta spokesman G Jayasimha told the BBC.
Peta say the chickens are kept in cramped and filthy conditions
The report released by the group says that antibiotics are "routinely fed" to healthy livestock and poultry to make them gain weight faster and to compensate for unsanitary living conditions.
"Poultry sold under such unhygienic conditions is a serious health hazard," it says.
The report says that chickens are forced to reach their slaughter weight in just 40-42 days which means that their legs, heart and lungs cannot keep pace with the rapidly growing body weight.
It says this leads to various problems including congestive heart failure and ascites - a pooling of body fluids in the abdomen.
"For many birds, leg problems are so severe that they are unable to reach food and water. During transportation to slaughter - which involves long rides in all weather extremes - broken bones commonly occur.
"After they arrive at abattoirs, chickens are rapidly shackled and hung by their feet from conveyors in mechanised slaughterhouses. Many are often dumped into scalding hot de-feathering tanks while still conscious," the Peta report says.
Poultry farmers have rejected the allegations.
"The Indian poultry sector is one of the best managed ones in this region. Our practices are often compared to those in developed countries," said Madan Maity, chairman of the West Bengal chapter of National Egg Coordination Committee, an organisation of the poultry owners.
"We definitely maintain high standards of health and hygiene including vaccination," he said.