Abstract
Simple SummaryIn the tropical and subtropical regions, heat stress is the main limiting factor of poultry industries. In this context, broilers are more liable to thermal stress due to their fast growth, rapid metabolic rate, and high level of production. The aim of the current work was to analyze changes in the brain serotonin, energy metabolism, antioxidant biomarkers, and blood chemistry of broiler chickens subjected to chronic thermal stress. Thermal stress disturbed the antioxidant defense system and energy metabolism and exhausted ATP levels in the liver tissues of broiler chickens. Interestingly, chronic thermal stress reduced the level of brain serotonin and the activity of CoQ10 in liver tissues.The aim of this paper was to investigate the effects of chronic thermal stress on the performance, energy metabolism, liver CoQ10, brain serotonin, and blood parameters of broiler chickens. In total, 100 one-day-old chicks were divided into two equal groups of five replicates. At 22 days of age and thereafter, the first group (TN) was maintained at a thermoneutral condition (23 ± 1 °C), while the second group (TS) was subjected to 8 h of thermal stress (34 °C). The heat-stressed group showed significantly lower ADFI but higher FCR than the thermoneutral group (p = 0.030 and 0.041, respectively). The TS group showed significantly higher serum cholesterol, ALT, and AST (p = 0.033, 0.024, and 0.010, respectively). Meanwhile, the TS group showed lower serum total proteins, albumin, globulin, and Na+ than the TN group (p = 0.001, 0.025, 0.032, and 0.002, respectively). Furthermore, the TS group showed significantly lower SOD and catalase in heart tissues (p = 0.005 and 0.001, respectively). The TS group showed significantly lower liver ATP than the TN group (p = 0.005). Meanwhile, chronic thermal stress significantly increased the levels of ADP and AMP in the liver tissues of broiler chickens (p = 0.004 and 0.029, respectively). The TS group showed significantly lower brain serotonin (p = 0.004) and liver CoQ10 (p = 0.001) than the TN group. It could be concluded that thermal stress disturbed the antioxidant defense system and energy metabolism and exhausted ATP levels in the liver tissues of broiler chickens. Interestingly, chronic thermal stress reduced the level of brain serotonin and the activity of CoQ10 in liver tissues.
Highlights
Thermal stress has been considered the main limiting factor of the poultry industry in tropical and subtropical regions [1]
The aim of the current work is to analyze changes in the brain serotonin, liver CoQ10, energy metabolism, antioxidant biomarkers, and blood chemistry of broiler chickens subjected to chronic thermal stress
The current study demonstrated a significant reduction in the level of serum total antioxidant capacity (TAC) of heat-stressed broilers
Summary
Thermal stress has been considered the main limiting factor of the poultry industry in tropical and subtropical regions [1]. Increased global warming will exaggerate heat stress-related problems [2]. When housing temperatures surpass comfort level, birds try to minimize metabolic heat production through a reduction in feed consumption [3], which reduces growth rate and profitability [4]. In this context, broiler chickens are more susceptible to thermal stress due to their high growth rate and related high metabolic heat production [5]. Several parameters are traditionally measured as thermal stress biomarkers in broiler chickens, including plasma concentrations of corticosterone, cholesterol, protein fractions, electrolytes, and antioxidants [6]. Thermal stress adversely affects cellular organelles, impairing oxidative metabolism and the functional structures of membranes [7]
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