MITIGATION OF HEAT STRESS IN BROILER CHICKENS USING DIETARY SUPPLEMENTATION OF MICROALGAE
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2023
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Abstract
Heat stress is a serious concern in the poultry industry, affecting their health and productivity. Prolonged exposure to high environmental temperatures can disrupt the basic cellular mechanisms, including the redox system, thereby impeding the production potential of broilers. This phenomenon can consequently lead to oxidative stress, predominantly resulting from the excessive formation of free radicals and reduced antioxidant enzymes. To effectively address the issue of heat stress, it is essential to include antioxidant-rich compounds in the poultry diet to ensure the proper functioning of the redox system. Microalgae (Spirulina platensis) are rich in antioxidants and have several health benefits in humans and animals. However, the effects of microalgae on the health and production in heat-stressed broilers, as well as the underlying mechanism, remains poorly understood. The primary objective of this study was to determine the effect of microalgae supplementation on the health and production of heat-stressed broilers. Cobb500 day-old chicks (N=144) were raised in litter floor pens (6 pens/treatment and 8 birds/pen). The chicks were divided into 3 treatment groups: a) no heat stress (NHS), b) heat stress (HS), and c) heat stress+3% microalgae (HS+MAG). The broilers in the HS+MAG group were fed a diet supplemented with 3% microalgae, whereas NHS and HS groups were fed a standard broiler diet. Broilers in the NHS were raised under standard temperature (20-24⁰C), while HS and HS+MAG broilers were subjected to cyclic heat stress from day 22-35 (32-33⁰C for 8 hours). All data are presented as mean ± SEM after performing one-way ANOVA Tukey’s post hoc test using GraphPad Prism. Microbial bioinformatics was performed in CLC Workbench and Spearman’s rank correlation was performed to establish correlations between microbiota and other parameters. The significance of the experiment was set at P<0.05. Heat stress significantly decreased the final body weight, whereas the supplementation of microalgae increased the final body weight of broilers (P<0.05). The expressions of ileal antioxidant (GPX3), immune-related (IL4), and tight-junction (CLDN2) genes were significantly increased in microalgae-supplemented broilers compared to heat-stressed broilers (P<0.05). The ileal villus height to crypt depth ratio was improved in microalgae-supplemented broilers (P<0.05). In addition, microbial alpha, and beta diversities were higher in the HS+MAG group compared to the HS group (P<0.05). The group that received microalgae supplementation exhibited an increase in volatile fatty acid-producing bacteria at the genus level, including Ruminococcus, Ocillospira, Lactobacillus, Oscillobacter, Flavonifractor, and Colidextribacter. In conclusion, dietary supplementation of microalgae improved the growth performances of heat-stressed broilers by improving their physiogenomics and gut microbiota composition. Thus, the dietary inclusion of microalgae can potentially mitigate heat stress in broilers.
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Agriculture, antioxidant, broiler, health, heat stress, microalgae, performance
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126 pages
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