Different densities and group size in commercial [hen] layers. Comparisons between two housing systems

agricultura agriculture alojamiento de animales animal animal domestique animal housing animal production animales animals aves de corral aves domesticas birds buildings cage cages chickens consommation consommation alimentaire construcciones consumo consumo de alimentos consumption densidad density domestic animals domesticated birds egg production food consumption galliformes housing jaulas laying performance logement logement des animaux oiseau oiseau domestique performance de ponte pollo poulet poultry production production animale production d'oeufs rendimiento en la postura vertebrados vertebrates vertebre vivienda volaille zootechnie zootechny zootecnia