Welfare of broilers: a review

Abstract

Selection for fast early growth rate and feeding and management procedures which support growth have lead to various welfare problems in modern broiler strains. Problems which are directly linked to growth rate are metabolic disorders causing mortality by the Sudden Death Syndrome and ascites. Fast growth rate is generally accompanied by decreased locomotor activity and extended time spent sitting or lying. The lack of exercise is considered a main cause of leg weakness, and extreme durations of sitting on poor quality litter produces skin lesions at the breast and the legs. Management factors which slow down early growth alleviate many welfare problems. Alternatively it may be considered to use slow growing strains which do not have the above mentioned welfare problems. Since growth is a main economical factor, there are problems of acceptability of these measures in the commercial broiler production. Stocking density is a central issue of broiler welfare. It is evident, that the influence of stocking density on growth rate and leg problems acts through its influence on litter and air quality. High moisture content of the litter enhances microbial activity, which in turn leads to increase of temperature and ammonia in broiler houses, and thus, high incidence of contact dermatitis. High stocking density impedes heat transfer from the litter surface to the ventilated room. This restricts the efficacy of conventional ventilation systems in alleviating heat stress. Lighting programmes with reduced photoperiods are considered essential for the stimulation of locomotor activity and the development of a circadian rhythm in the birds. Extended dark periods, however, reduce growth when applied in the first weeks of age. Compensation occurs when the time of the production cycle is substantially increased. Various methods to enrich the environment have shown only moderate effects on the behaviour and physical conditions of broilers.

Welfare of broiler chickens

“…Secondary infections may further worsen the conditions of the birds. There is evidence that the contact dermatitis causes pain and thus is a matter of welfare (Bessei, 2006). Several risk factors are responsible for the onset of foot dermatitis including type, depth and condition of litter, stocking density, feed composition, light and climate.…”

Evaluation of Free-Range broilers using the welfare quality® protocol

“…Continuous exercise contributes to increase bone strength in poultry (Bizeray et al, 2000) and rapid growth rate is the main cause of locomotion problems (Bessei, 2006). The observed low number of birds panting or huddling and presenting lameness indicates good AW of the evaluated broilers.…”

“…Many AW critical points have been identified in industrial broiler production systems, such as skeletal disorders, locomotion problems, high stocking densities, and poor litter quality (Bessei, 2006). On the other hand, alternative production systems, such as free-range poultry production, may potentially improve bird welfare.…”

Animal health aspects of adaptation to climate change: beating the heat and parasites in a warming Europe

“…a broiler production shed) by a 'heat wave' or long-term increase in maximum temperature exceed the ventilation capacity, then, in addition to potential heat stress on the birds, other variables will be affected. Water usage by the stressed birds will increase (May and Lott, 1992;Belay and Teeter, 1993), litter quality may deteriorate, this will result in increased incidence of pathology and losses (Bessai, 2006;Manning et al, 2007;Meluzzi et al, 2008;Alain et al, 2009;Kyvsgaard et al, 2013) and the final wet litter will present problems of emissions and disposal (Topper et al, 2008;Singh et al, 2009). Obviously, during animal transport (catching/handling/ loading/in transit) and the associated procedures, similar factors will determine the on-board environment for the animals and their effects.…”