Age-related effects of feeder space availability on welfare of broilers reared to 56 days of age1 Part 2: Blood physiological variables

Authors: Olanrewaju, Hammed; Purswell, Joseph - Jody; Collier, Stephanie; BRANTON, SCOTT - Retired ARS Employee

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2021
Publication Date: 3/2/2022
Publication URL: https://handle.nal.usda.gov/10113/7622205
Citation: Olanrewaju, H.A., Purswell, J.L., Collier, S.D., Branton, S.L. 2022. Age-related effects of feeder space availability on welfare of broilers reared to 56 days of age1 Part 2: Blood physiological variables. Poultry Science. 101:101698. https://doi.org/10.1016/j.psj.2022.101698.
DOI: https://doi.org/10.1016/j.psj.2022.101698

Interpretive Summary: In adequate feeder space availability for potentially have an adverse impact on blood homeostasis and welfare of birds, which can result in production inefficiencies, compromised animal well-being and increased animal morbidity and mortality. Currently, consumers perceive feeder space availability to be an important factor that affect animal welfare and the application of optimal welfare standards with adequate feeder space availability is believed to result in a higher product quality. In each trial of 2 trials, the effects of four different feeder space treatments on welfare of broiler chickens reared to 56 days of age on blood physiological variables were evaluated. Results show there was no effect of feeder space on most of the selected physiological variables. However, all observed changes were within physiological ranges of broilers. Plasma corticosterone and glucose concentrations were not affected by feeder space and age, indicating absence of physiological stress. The results are in broad agreement with those reported in the literature and on homeostatic variation of broilers grown to heavy weights. In conclusion, expanding feeder space does not improve the welfare of broilers grown to heavy weights.

Technical Abstract: Consumption of poultry meat has increased dramatically and is expected to continue due to the relative price-competitiveness as compared to other meat products. However, the rapid growth and increased production efficiency of modern genetic strains is perceived to negatively impact the welfare of the animal. Hematological analyses including changes in acid-base balance provide a thorough evaluation of the welfare and systemic homeostasis in both animals and humans. This study investigated the effects of feeder space availability on welfare of broilers grown to heavy weights using blood physiological variables. In each study, a total of 1440 1-d-old chicks (straight-run) were obtained from a commercial hatchery. Chicks were equally and randomly allocated to 32 pens based on feeder space treatment. Treatments were four different feeder space allocations: 2.3 (Single feeder), 2.30, 4.60, and 6.90 cm/bird. To maintain uniform bird:feeder floor space, three feeders were installed in each pen, except for the single feeder pen. Blood samples (3 ml) were collected from the brachial wing vein of 3 birds per pen on d 27 and 55, which were then analyzed immediately for whole blood physiological variables. The remaining blood samples were centrifuged to collect plasma that was used for corticosterone and thyroid hormones analysis. Results show there was no effect of feeder space on most of the selected physiological variables, but age had significant effects on most of the examined variables. However, all observed changes were within physiological ranges. Plasma corticosterone was not affected by feeder space and age, indicating absence of physiological stress. The results are in broad agreement with those reported in the literature and on homeostatic variation of broilers grown to heavy weights. In conclusion, expanding feeder allowance does not enhance the welfare of broilers grown to heavy weights.