Effect of stocking density and dietary antimicrobial inclusion of male broilers grown to 35 days of age1 Part 2: Blood physiological variables

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

Submitted to: International Journal of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2020
Publication Date: 9/10/2020
Citation: Olanrewaju, H.A., Purswell, J.L., Collier, S.D., Branton, S.L. 2020. Effect of stocking density and dietary antimicrobial inclusion of male broilers grown to 35 days of age1 Part 2: Blood physiological variables. International Journal of Poultry Science. 19:447-454.
DOI: https://doi.org/10.3923/ijps.2020.447.454

Interpretive Summary: Stocking Density (SD) high SD may restrict bird movement, increase litter moisture, microbial growth, and impede air flow among others, thereby affecting production performance and welfare. Currently, consumers perceive stocking density to be one of the most important factors that influence animal welfare and the application of optimal welfare standards where low stocking density is believed to result in a higher product quality. Furthermore, antimicrobials have been added in animal feed to improve growth, feed conversion ef'ciency and to prevent diseases. However, there are concerns that the use of antibiotics leads to development of antimicrobials resistance that posing a potential threat to human health. Therefore, a significant expansion of antibiotic-free (ABF) broiler production is expected to continue as demand for poultry products continues to increase. In each trial of 2 trials, we evaluated the effects of stocking density, dietary antimicrobial inclusion and their interaction if any on selected whole blood physiological variables of male broilers grown to 35 days of age to ensure the health and welfare of broilers. Results show there was no effect of stocking density on any of the selected physiological variables. However, in comparison to broilers fed with ABF diet, broilers with AGP+ had levels of pO2, sO2, SaO2, Ca2+, and K+ which were within physiological ranges. In addition, blood glucose and plasma corticosterone concentrations were not affected by treatments, suggesting an absence of physiological stress. In conclusion, stocking densities up to 39 kg/m2 with appropriate environmental management regardless of antimicrobial addition in the diets may be suitable for both poultry integrators and contract growers to enhance broilers production efficiency without compromising the welfare of broilers grown to 35 days of age.

Technical Abstract: This study investigated the effects of recommended stocking densities and dietary antimicrobial inclusion of male broilers grown to 35 days of age on selected blood physiological variables. Materials and Methods: In each study, a total of 1024 1-d- old Ross x Ross 708 male chicks were randomly distributed into 32 pens based on 4 assigned stocking density treatments. The treatments consisted of 4 densities (27, 29, 33, 39 kg/m2) and 2 diets (AGP+, ABF) arranged in a 4 × 2 factorial with eight replicates. Conventional (antimicrobial-growth-promoters, AGP+) and antibiotic free (ABF) diets were equally assigned to each pen with feed and water provided ad libitum. Blood samples were collected from the brachial wing vein of 3 birds per pen on d 15, 28, and 35, which were then analyzed immediately for whole blood physiological variables. Blood plasma samples were analyzed for T3, T4, and corticosterone. Results: Results show there was no effect of stocking density on any of the selected physiological variables. However, in comparison to broilers fed with ABF diet, broilers with AGP+ had significant higher levels of pO2, sO2, SaO2, Ca2+, and K+ which were within physiological ranges. In addition, blood glucose and plasma corticosterone concentrations were not affected by treatments, suggesting an absence of physiological stress. In conclusion, stocking densities up to 39 kg/m2 with appropriate environmental management regardless of antimicrobial addition in the diets may be suitable for both poultry integrators and contract growers to enhance broilers production efficiency without compromising the welfare of broilers grown to 35 days of age.