In 2005, the European Commission published a draft law setting out hygiene standards for the ammonia-ridden litter produced by the industry, rules for ventilation inside mostly windowless sheds and even lighting regulations for the sector.

Since then, the main problem for EU governments has been the sensitive point of how many birds may be packed into a specific area: a density level key to the profits of broiler farmers.

Two years ago, the Commission said 30 kg should be a base standard, but with leeway for intensive-rearing operations to raise this to 38 kg if welfare standards were met in areas like litter and ventilation. Several countries said this was too low.

The final compromise reached by ministers was for a maximum stocking density of 33 kg of broilers by weight per square metre, with an option to go to 39 kg under certain conditions.

"We have a deal, it's a good compromise. We would have preferred the original proposal ... but this significantly improves the situation in the sector compared to what it is today," EU Health Commissioner Markos Kyprianou said.

Current stocking densities vary widely across the EU. The European average is 40 kg of bird weight per square metre, and slightly higher in some countries like France and the Netherlands.

Until now, Europe has had no specific laws to control the broiler trade. A few countries, like Sweden and Denmark, do have strict laws in place but most have none.

Under even stricter criteria, such as not exceeding maximum mortality rates over a specified period of time, EU countries can allow their broiler industries to use a density of as much as 42 kg per square metre.

"It (42 kg) is conditional and it's not the rule. To reach that high (level), you have to fulfil a lot of other criteria," Kyprianou told reporters after a meeting of EU farm ministers.

Nearly 46 billion such chickens are reared worldwide every year, more than 5 billion of them in the European Union.