Doctoral Dissertations
Date of Award
5-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Animal Science
Major Professor
Yang Zhao
Committee Members
Jun Lin, Hao Gan, Tom Tabler, Maria Prado
Abstract
The U.S. broiler industry is a cornerstone of the nation’s food system and economy, leading global production and delivering affordable, high-quality protein. However, its rapid growth presents challenges, particularly regarding animal welfare. Key gaps include the economic and resource impacts of slower-growing strains, inconsistent research on stocking density and lighting effects, and limited adoption of advanced welfare technologies due to high costs. Addressing these challenges requires collaboration, targeted research, and sustainable solutions.
This dissertation examines the effects of growth rate, stocking density, and lighting intensity on broiler welfare and behavior, offering strain-specific management strategies to enhance production performance and welfare in the poultry industry.
Chapter one reviews gaps in balancing productivity and animal welfare. While slower-growing strains improve welfare, they increase costs and resource use, raising food security concerns. Research on stocking density reveals strain-specific responses but emphasizes environmental management’s role over density effects. Similarly, lighting intensity studies show inconsistent results. Emerging technologies like computer vision show potential for welfare assessment but face adoption barriers due to cost. Bridging these gaps demands rigorous research and practical, economically viable solutions.
Chapter two explores how growth rate and stocking density impact welfare. Reduced densities improve feather coverage, gait scores, and activity but may compromise feed conversion ratio (FCR) and lengthen production cycles.
Chapter three compares Ross 708 and Cobb 700 broilers under varying stocking densities. Lower densities improve feather cleanliness and footpad health but show minimal effects on production and welfare, supporting current stocking density standards (44 kg/m²).
Chapter four analyzes density and age effects on activity. High density increases early activity but reduces mobility by 56 days, with strain-specific behavioral responses.
Chapter five investigates lighting intensity. Higher light intensity improves activity, gait scores, and thermal regulation but increases feather loss, while lower intensity preserves feather coverage and reduces dermatitis but limits activity.
Chapter six highlights strain-specific lighting strategies. Ross broilers benefit from 20 lux, enhancing behaviors like stretching and preening, while Cobb 700 broilers adapt better to 5 lux, particularly during later growth stages. These findings emphasize tailored management strategies to optimize broiler welfare.
Recommended Citation
Zhou, Shengyu, "Broiler welfare and behavior as affected by management practices. " PhD diss., University of Tennessee, 2025.
https://trace.tennessee.edu/utk_graddiss/12327