How does stocking density affect pullet welfare?

Research was performed to understand detection of pullet welfare, which could allow for producers and researchers to develop practical and measurable stress markers in cage-free systems.

Meredith Johnson Headshot
Courtesy Big Dutchman
Courtesy Big Dutchman

Pullets appear to be unaffected by stocking density, according to the initial findings of a study conducted by Purdue University.

The research was performed to understand detection of pullet welfare, which could allow for producers and researchers to develop practical and measurable stress markers in cage-free systems. Higher stocking densities can potentially affect birds’ abilities to exhibit natural behaviors and easily access feed and water, as well as negatively impact health and production. Currently, there is no stocking density established for cage-free housed pullets in the U.S.

The experiment

Two strains of pullets, Lohman LSL-Lite and Lohman Brown-Lite, were housed at high (436.6 cmper chick) and low (1,059.16 cmper chick) stocking densities and evaluated for metabolic changes, immune function and production welfare measurements. 

To further support the college’s research and gauge the practicality of measuring potential stress markers on farms, a survey was created to evaluate producers’ opinions of pullet welfare and the use of welfare parameters in real-time. The survey aims to identify what producers find manageable on commercial farms and how viewpoints could differ depending on demographics. 

To take the survey, click here.

The survey was created by researchers at the Purdue University Animal Science department and is anonymous and confidential (IRB# 2021-1472). Please contact Meagan Abraham DVM, Purdue University PhD candidate, at [email protected] with questions. The deadline to complete the survey is March 31, 2022.

Additional studies

The findings in the initial study created two questions for Abraham: would adding an additional stressor elicit a measurable stress response in pullets and would the stress response differ in pullets and adult hens? 

In a second study, extreme stressors were applied in hopes of detecting a stress response through measurable differences in physiology, immunology, production, bird condition and behavior. The same two pullet strains used in the initial study were utilized and a third, higher, stocking density was added. Additionally, one half of each treatment had reduced feeder space. 

In a third study, stress levels were induced in pullets by injecting the hormone ACTH at 6, 17, and 25 weeks of age to activate an HPA stress pathway. Dr. Darrin Karcher, Purdue University Associate Professor and Poultry Specialist, hopes this study will help identify if pullets are resistant to stress and if the stress response is altered in birds depending on age.

The second and third studies have concluded and the data is being analyzed.

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