The Effects of Heat Stress on the Physiology, Immunity, and Behavior of Livestock and Poultry

Dear Colleagues,

Heat stress refers to the non-specific physiological responses in livestock and poultry triggered by impaired thermoregulation under high-temperature environments. Physiological effects include reduced feed intake, slowed growth, decreased reproductive performance (e.g., lower egg production, reduced sperm viability), metabolic disorders (e.g., blood glucose fluctuations, electrolyte imbalances), and organ damage (e.g., hepatic lipid accumulation, alveolar destruction). Immunologically, heat stress suppresses immune organ development, lowers antibody levels, and increases disease susceptibility. Behavioral abnormalities such as open-mouth breathing, reduced activity, and increased water intake are commonly observed. Prolonged heat stress further leads to endocrine disruption (e.g., elevated cortisol, abnormal thyroid hormones) and elevated mortality, severely impacting farming efficiency.

(1) Special Issue Overview

Focus: Multidimensional mechanisms of heat stress on physiological, immunological, and behavioral responses in livestock and poultry, with a focus on species-specific THI thresholds and newly established indices for diverse species.

Scope: This Special Issue will cover major species (pigs, chickens, cattle, buffaloes, sheep, goats) under acute/chronic heat stress. Key areas include the following:

THI diversity: over 20 THI variants exist globally, tailored to species’ thermoregulatory capacities (e.g., cattle tolerate THI up to 86, while pigs exhibit stress at THI ≥75 due to lack of sweat glands);

Comfort zones;

Dairy cattle: THI <68 (comfort), 68-72 (mild stress), 72-79 (moderate), ≥80 (severe);

Beef cattle: breed-specific thresholds (e.g., Angus at THI 86, Brahman at 96);

Poultry: THI ≥70 triggers stress (due to feather insulation);

Buffaloes: THI 65-80 with species-specific mild/moderate/severe ranges [1];

Mitigation strategies: environmental control (shade, cooling), nutritional interventions, and heat-tolerant breed selection;

Purpose: to systematically synthesize heat stress impacts, evaluate mitigation efficacy, and provide evidence-based solutions for farming efficiency and animal welfare;

(2) Literature Contribution

This Special Issue bridges gaps in fragmented research by integrating cross-species THI analyses and 2025-2026 advancements (e.g., molecular mechanisms, climate change adaptations). It elucidates interconnections between heat stress-induced immunosuppression, reproductive failure, and metabolic dysfunction, while coupling these with practical interventions (nutritional optimization, precision cooling). Key contributions include the following:

New THI indices: species-specific indices for buffaloes (THI 65-80), sheep (THI 56-84 in Amazonian climates), and poultry (THI ≥70).

Climate resilience: THI forecasts using CMIP6 models to predict extreme heat stress risks in livestock by 2050 [2].

Mechanistic insights: linking THI thresholds to gene expression (e.g., heat shock proteins in buffaloes) and endocrine disruptions.

Applied solutions: smart climate control technologies (e.g., automated cooling systems) and breed selection for heat tolerance.

By linking mechanistic insights to applied solutions, this work advances heat stress research from empirical to scientific frameworks, guiding future directions in heat-tolerant breed development and precision livestock farming.

References

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC8275759/

[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC9292043/

Dr. Shu Tang
Guest Editor

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• heat stress
• livestock
• species-specific thresholds
• physiological well-being
• immunosuppression
• behavioral abnormalities
• metabolic disorders
• reproductive performance
• nutritional intervention
• temperature–humidity index (THI)
• precision livestock farming