Hunger in farm animals
Most adult captive animals need to have their energy intake rationed to avoid obesity, but this occurs to a greater extent in some farm animals. The generation of animals destined for slaughter (broiler chickens, finisher pigs) have been genetically selected for rapid growth and are generously fed to maximise growth during the juvenile phase before being slaughtered prior to adulthood. The parents of this slaughter generation (broiler breeder chickens, sows) share a good deal of their offspring’s genetic potential for rapid growth, so must be food restricted to avoid obesity and ensure good physical and reproductive health and function. This food restriction results in the welfare problem of hunger, especially evident in behaviour signs such as increased foraging and activity which can become stereotypic. Dawkins (2003) argued that good animal welfare means animals that are healthy and have what they want. In feeding parent animals, it seems we have to make a choice between these as both aren’t currently possible. One solution might be changes to genetic breeding goals. In poultry, slower-growing or specialised breeds including dwarf breeds can be reared without feed restriction. Selection for juvenile rapid growth separately from adult growth potential might be another solution although the genetic correlation between these traits is large. Another possible solution is to reduce energy density of the diet (qualitative restriction), for example by adding fibre. EU rules require that sows have access to fibre in their diet or environment (e.g. straw), and broiler breeder diets have been reduced in energy density. But if energy restriction is the same, is welfare improved? Or does ‘metabolic hunger’ remain? There are difficulties in interpreting many existing measures of hunger/satiety. We are developing and investigating new behavioural and physiological measures of hunger to shed new light on this difficult area.
Other Titles/Title of Conference
International Society for Applied Ethology: UK & Ireland Regional Meeting, Edinburgh, UK