Pre-hatch thermal manipulation of chicks’ embryo and post-hatch baicalein supplementations: A sustainable strategy to mitigate heat stress in broiler chickens

Abstract

Elevated environmental temperatures can cause heat stress in broiler chickens, impacting their health and production efficacy. Various dietary, managerial, and genetic strategies have been evaluated with some efficacy in alleviating heat stress (HS) in broilers. Therefore, it is essential to develop innovative strategies to mitigate HS for sustainable broiler production. This dissertation explores the effects of embryonic thermal manipulation and post-hatch baicalein supplementation on hatching performance, embryonic growth, metabolism, overall growth performance, gut health, muscle functional capacity, and immunity in broiler chickens. Six hundred fertile Cobb 500 eggs were incubated for 21 d. After candling on embryonic day (ED) 10, 238 eggs were thermally manipulated at 38.5 °C with 55% relative humidity (RH) from ED 12 to 18, then transferred to the hatcher (ED 19 to 21, standard temperature) and 236 eggs were incubated at a controlled temperature (37.5 °C) till hatch. After hatch, 180-day-old chicks from both groups were raised in 36 pens (n = 10 birds/pen, 6 replicates per treatment). The treatments were: 1) Control, 2) thermal manipulation (TM), 3) control heat stress (CHS), 4) thermal manipulation heat stress (TMHS), 5) control heat stress supplement (CHSS), and 6) thermal manipulation heat stress supplement (TMHSS). All birds were raised under the standard environment for 21 d, followed by chronic heat stress from d 22 to 35 (32–33 °C for 8 h) in the CHS, TMHS, CHSS, and TMHSS groups. A thermoneutral (22–24 °C) environment was maintained in the Control and TM groups. RH was constant (50% ± 5%) throughout the trial. All the data were analyzed using one-way and two-way ANOVA in R and GraphPad software at P < 0.05 and are presented as mean ± SEM. CLC Genomics Workbench 25.0.1 and the CLC Microbial Genomics module were utilized for bioinformatics analysis of microorganisms. In conclusion, Pre-hatch TM and post-hatch baicalein supplementation in heat-stressed birds mitigated the detrimental effects of heat stress on chickens' growth performance, increased hatchability, embryonic growth, and metabolism, as well as post-hatch VFA production, muscle cell proliferation capacity, and immunity. Additionally, it promoted gut health by increasing beneficial microbial communities. TM is essential for sustainability as it enhances feed conversion efficiency, reduces feed intake to reach comparable sizes at lower costs. Additionally, TM contributes to improved animal welfare, enhancing heat tolerance and promoting better health. It also reduces incubation time by 6 hours, which lowers energy consumption and production costs, making poultry products more economically viable. TM is crucial in establishing a more sustainable food production system while ensuring animal welfare. This research is crucial for addressing food insecurity in the era of global warming. TM has significant potential in alleviating heat stress and protecting the poultry industry in the United States and beyond. Ultimately, it aims to have a significant impact on the poultry industry.