Further Studies of Density and Group Size Effects in Caged Hens of Stocks Differing in Fearful Behavior: Productivity and Behavior ,

Abstract

Two experiments were done involving moderately inbred strains known to differ in escape and avoidance behavior. Hens of those strains and of a cross between them (second experiment only) were compared for fear-related behavior, feather damage and loss, and productivity traits when housed four or eight/cage at densities of 348 (high), 464 (medium), and 580 (low) cm2/bird. Hens that died were replaced. Strain cross hens did not differ from parental strain hens in nervousness, feathering scores, or survival, but exhibited hybrid vigor for rate of lay, egg weight, daily egg mass, and age at sexual maturity.Density, but not group size, affected rate of lay, daily egg mass, and percentage survival. Hens in high density cages were adversely affected but those in medium and low density cages did not differ from each other. Nervousness and feather loss were influenced adversely and stepwise by higher densities, and hens in cages of eight were more nervous and had greater feather loss and damage than those in low density cages.There were no interactions between stock and density or group size for any of the traits measured. However, there was an interaction of stock with age period for both egg weight and daily egg mass. Strain cross hens had an advantage over parental hens during the earlier part of the laying year because of their earlier maturity and relatively heavier egg weights during that period.There was an interaction between density and group size for rate of lay and egg mass during the second and larger scale experiment only; hens in eight-bird cages performed at lower levels than did hens in four-bird cages only when kept at high density. There was a strong interaction between density, but not group size, and age; adverse effects of the high-density cage environment became more evident as time passed.