Document Type : Research Paper
Extended Abstract
Introduction
Heat stress is one of the most persistent challenges in poultry production, particularly in tropical and subtropical regions where elevated ambient temperatures impair feed intake, metabolic balance, endocrine activity, immune function, and growth performance. Broiler chickens are highly susceptible to thermal stress because of their rapid growth rate and high metabolic heat production, making them a critical model for interventions aimed at mitigating stress-related performance decline. Nutritional strategies, especially the use of anti-stress supplements containing vitamins, electrolytes, antioxidants, or herbal components, have drawn considerable attention for their potential to stabilize physiological responses under heat stress and improve overall productivity. Among commercial supplements, “Stress Calm” has been formulated to reduce physiological stress and support metabolic and endocrine stability. Despite promising claims, scientific evidence evaluating its efficacy under both normal and heat-stress conditions remains limited.
The present study was designed to investigate the effect of different dietary inclusion levels of anti-stress on growth performance, feed efficiency, carcass characteristics, and selected blood parameters of broiler chickens reared under normal temperature and heat-stress conditions. The study aimed to determine whether anti-stress supplementation improves performance and physiological responses beyond those of birds receiving a basal diet alone, and whether its effects differ across varying environmental temperatures. Based on previous literature, we hypothesized that anti-stress would (a) enhance weight gain and feed efficiency, (b) improve carcass yield, and © modulate key blood biomarkers such as thyroid hormones, oxidative stress indicators, and immune parameters. Identifying effective nutritional interventions for mitigating heat stress is essential for poultry producers, veterinarians, nutritionists, and feed formulation specialists. This research employs an explanatory experimental design aligned with a postpositivist approach, enabling objective evaluation of treatment effects and interaction patterns under controlled environmental conditions.
Materials and methods
A controlled experimental study was conducted using 240 one-day-old male Ross broiler chickens over a 42‑day period. Birds were randomly assigned to four dietary treatments containing 0, 1.5, 3, and 5 g/kg of the anti-stress commercial anti-stress supplement. Each treatment was evaluated under two environmental conditions: normal temperature and heat stress. Each of the eight treatment combinations included six replicates. All birds were housed in identical cages with ad libitum access to feed and water. Diets were formulated based on standard recommendations and provided in four phases: starter (0–10 days), grower (11–24 days), finisher 1 (25–35 days), and finisher 2 (36–42 days).
Outcome measurements included average daily weight gain, feed intake, feed conversion ratio (FCR), live body weight, and European Production Efficiency Index (EPEI). At day 43, birds were slaughtered to determine carcass yield and relative organ weights (breast, thigh, liver, gizzard, heart, abdominal fat). At 42 days of age, blood samples were collected from the wing vein for analysis of glucose, cortisol, GPX, malondialdehyde, T3, T4, white blood cell counts, heterophil-to-lymphocyte ratio (H/L), and ND antibody titer. Serum was separated by centrifugation and used for biochemical and hormonal assays.
All procedures adhered to ethical guidelines for the care and use of animals in research. Collected data were analyzed using the SAS software package. Mean comparisons were performed using Duncan’s multiple range test, and significance was declared at P<0.05.
Results and Discussion
Supplementation with anti-stress significantly improved several key performance indicators. Birds receiving 1.5, 3, or 5 g/kg anti-stress exhibited higher average daily weight gain and greater final live body weight compared with the control group (P<0.05). Feed conversion ratio improved notably in the 1.5 and 5 g/kg groups, indicating enhanced feed efficiency. The EPEI also increased in all anti-stress –supplemented treatments, with the highest values observed in the 5 g/kg group.
Environmental temperature significantly influenced performance. Birds reared under normal temperature had higher weight gain and final body weight than those exposed to heat stress (P<0.05). Nonetheless, anti-stress supplementation partially mitigated the negative effects of heat stress, as supplemented birds showed better performance than heat‑stressed birds in the control treatment.
Carcass evaluation demonstrated that anti-stress significantly increased carcass weight across all supplemented groups (P<0.05), while relative percentages of major carcass components (breast, thigh, abdominal fat) were not significantly altered. Environmental temperature influenced thigh percentage and heart relative weight, with heat‑stressed birds presenting slightly higher values.
Blood analysis revealed that T3 concentrations were significantly higher in all anti-stress–supplemented birds compared to controls (P<0.05), suggesting improved thyroid activity and metabolic regulation. Other blood metabolites such as glucose, MDA, GPX, cortisol, and ND titer remained statistically similar among treatments, although heat-stressed birds showed higher WBC counts and a higher H/L ratio, consistent with physiological stress responses. Anti-stress did not significantly modify oxidative stress markers but contributed to hormonal stabilization.
Economic analysis indicated that the 1.5 g/kg anti-stress treatment generated the highest net profit and profit percentage, outperforming all other treatments due to a favorable balance of improved FCR, higher final body weight, and reasonable supplement cost.
Conclusion
This study demonstrates that supplementation with the commercial anti‑stress product anti-stress improves growth performance, carcass yield, and thyroid hormone levels in broiler chickens, both under normal and heat‑stress conditions. The supplement enhanced weight gain and feed efficiency while also increasing carcass weight without altering major carcass component ratios. Although heat stress impaired overall performance and altered hematological responses, anti-stress supplementation reduced the severity of performance losses and supported better metabolic regulation.
The findings highlight the practical significance of tailored nutritional strategies for mitigating heat-stress–induced performance decline in broiler production. From an industry perspective, using 1.5 g/kg anti-stress `appears to offer the best economic return, making it a promising option for poultry operations in warm climates. Future research should explore long-term physiological effects, potential synergistic interactions with antioxidants or electrolytes, and the mechanisms through which anti-stress modulates endocrine and metabolic pathways.
Author Contributions
Behzad Sadighi and Hossein Moravej, contributed to conception, design, data collection, statistical analysis, and drafting of the manuscript. All authors approved the final version for submission.
Data Availability Statement
This article contains all the data that were created or evaluated during the research.
Acknowledgements
The authors would like to sincerely thank the members of Department of Animal Science, College of Agriculture & Natural Resources, University of Tehran, Karaj, Iran for the approval and support of this research.
Ethical considerations
All experimental procedures involving animals were reviewed and approved by the Committee on the Ethics of Animal Experiments of the Faculty of Agricultural Sciences and Natural Resources, University of Tehran (Karaj). All protocols complied with institutional guidelines for the care and use of animals in research.
Conflict of interest
The author declares no conflict of interest.
