The physiological and economical effect of density and cage size on two genetically different strains of commercial layers

Abstract

A series of studies was designed to determine the effect of bird numbers per cage and floor area per bird on laying performance. Adrenal weights were also measured on selected treatments. Two strains of commercially available birds, an incrossbred strain and a California Gray x White Leghorn cross, with body weights at housing time of about 1,400 and 1,650 grams, respectively, were used. A total of 1,134 birds of each strain were randomly assigned to three different cage sizes and three densities within each cage size. A general decline in final average body weight and average hen-day egg production occurred as bird density per cage increased. The bird number per cage and floor area per bird had a significant affect on the average egg size, percent large eggs, and feed efficiency. For the strain of incrossbred birds used for this study, three 2 or four birds per cage allowing a minimum of 464 cm of floor space per bird appeared to be the optimum social arrangement for minimum stress and maximum performance. For the California Gray x White Leghorn cross the optimum number of birds appeared to be two or three birds per cage if allowed at least 580 cm of floor space. Floor area per bird appeared to be regulated to some degree by the total body mass within a cage. The adrenal weights based on milligrams of gland per gram of body weight increased as the bird densities per cage increased.