Cage-free Pullet Density: Production and Welfare Outcomes

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Institution: Purdue University

Principal Investigator:
Darrin M. Karcher, Ph.D.
Assistant Professor, Extension Poultry Scientist
Purdue University
3034 Creighton Hall of Animal Sciences
270 South Russell Street
West Lafayette, IN 47907

The environment and experiences that a pullet goes through in the first 16 weeks of life can have lasting impacts on behavior, welfare, health and productivity of the bird as an adult. There is limited information to guide management during the pullet phase, including guidelines on stocking density. Additionally, more information is needed on stress and welfare during the pullet phase, and currently there are few validated ways to measure these aspects of the pullet’s experience. Historically, research has focused on resource-based measures of welfare, which do not provide information about the pullet’s response to her environment but instead provides an outline of resource standards prior to bird placement. Animal-based welfare measures can provide insight into how the bird is feeling and how she has responded to her environment. This project sought to improve pullet welfare in cage-free rearing systems through two objectives: 1) develop outcome-based (animal-based) welfare measures for pullets reared at different densities in a research setting, and 2) field test outcome-based measures with commercial pullet growers.

Two studies of external stressors were applied to white and brown strains of Lohmann pullets. Bird-based welfare parameters were assessed, including evaluation of bird appearance through feather coverage, foot condition and keel condition. Body weight, uniformity, feed consumption and feed conversion ratio (FCR) were also analyzed.

In the first study, both strains were housed at high (670 cm2/bird) and low stocking densities (1352 cm2/bird). Stocking density affected only relative bursal weight (%), which was higher in the low stocking density. In the brown strain, high stocking densities resulted in decreased body weight uniformity and worse feather coverage, but low stocking density was associated with an improved FCR. In the white strain, higher density resulted in better uniformity and feather coverage but a worse FCR.

The second study used the two strains, two feeder space allocations and three stocking densities – high (154.45 cm2/bird), medium (518.76 cm2/bird) and low (1,247.38 cm2/bird). In this study, high stocking densities were associated with poorer feather condition but improved FCR. Reduced feeder space was associated with elevated or worse FCR and poorer IgG antibody titers.

There were strain and age differences detected in most parameters for both studies, indicating that the parameters were sensitive enough to detect differences but that few differences were due to either stocking density or feeder space stressors alone. The results of the two studies appear to illustrate a resilience to stress during the pullet phase. Researchers were unable to identify any outcome measures of stress and welfare during the pullet phase. As a result, the second objective was not achieved.

At all the densities and feeder spaces used, pullets appeared to thrive, meaning any of the densities or feeder spaces used is acceptable for use in the field.