Welfare of broiler chickens

Selection for fast early growth-rate, and feeding and management procedures to support such growth, have led to various welfare problems in modern broiler strains.

Affected birds suddenly start to flap their wings, lose their balance, sometimes cry out and then fall on their backs or sides and die, usually all within a minute.

[3] Ascites is characterised by hypertrophy and dilatation of the heart, changes in liver function, pulmonary insufficiency, hypoxaemia and accumulation of large amounts of fluid in the abdominal cavity.

[3] There is a high frequency of skeletal problems in broilers, mainly in the locomotory system, including varus and valgus deformities, osteodystrophy, dyschondroplasia and femoral head necrosis.

Several research groups have developed "gait scores" (GS) to objectively rank the walking ability and lameness of broilers.

This contact dermatitis is characterised by hyperkeratosis and necrosis of the epidermis at the affected sites; it can take forms such as hock burns, breast blisters and foot pad lesions.

[3] There is a reduction of feed intake and reduced growth rate when stocking density exceeds approximately 30 kg/m2 (6 lb/sq ft) under deep litter conditions.

[1] In a large-scale experiment with commercial farms, it was shown that the management conditions (litter quality, temperature and humidity) were more important than stocking density.

[citation needed] Once the broilers have reached the target live-weight, they are caught, usually by hand, and packed live into crates for transport to the slaughterhouse.

In the UK, of broilers that were found to be 'dead on arrival' at the slaughterhouse in 2005, it was estimated that up to 40% may have died from thermal stress or suffocation due to crowding on the transporter.

[3] Slaughter is done by hanging the birds, fully conscious, by their feet upside-down in shackles on a moving chain, stunning them by automatically immersing them in an electrified water bath and exsanguination by cutting their throats.

Meat broilers have been artificially selected for an extremely high feeding motivation, but are not usually feed-restricted, as this would delay the time taken for them to reach slaughter-weight.

An experiment on broilers' food intake found that 20% of birds allowed to eat as much as they wanted either died or had to be killed because of severe illness between 11 and 20 weeks of age – either they became so lame they could not stand, or they developed cardiovascular problems.