Impact of Heat Stress on Growth Performance and Reproductive Efficiency in Broiler Chickens

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

Poultry production remains a cornerstone of food security and rural livelihoods in many parts of the world. In developing countries such as Nigeria, broiler chicken farming has become a major source of animal protein, income, and employment. The poultry industry contributes significantly to the agricultural sector by supplying meat and eggs that meet the nutritional needs of a growing population. Despite these benefits, environmental factors such as heat stress continue to limit the full potential of broiler production (Aengwanich, 2017).

Heat stress occurs when birds are exposed to high ambient temperatures that exceed their ability to maintain normal body temperature. In tropical and subtropical regions, temperature levels often rise above 30°C, creating thermal discomfort for broilers. As a result, birds respond by reducing feed intake, increasing water consumption, and altering physiological functions to maintain balance (Attia et al., 2018). Unfortunately, these adjustments often lead to decreased growth performance, reduced feed efficiency, and higher mortality rates.

Moreover, heat stress affects reproductive performance by interfering with hormonal balance and reducing fertility in breeding flocks. According to Lara and Rostagno (2013), elevated temperatures disrupt reproductive hormones such as luteinizing hormone and follicle-stimulating hormone, which are essential for egg production and sperm viability. Over time, this leads to lower hatchability and poor reproductive success.

The growing impact of global climate change has intensified the challenge of heat stress in poultry production systems. The Intergovernmental Panel on Climate Change (IPCC, 2021) reported a steady rise in global average temperatures, particularly in tropical regions. Consequently, poultry producers now face the dual challenge of maintaining high productivity while minimizing the physiological and economic effects of heat exposure.

To adapt, farmers are exploring several strategies such as improving housing ventilation, using heat-tolerant breeds, adjusting feeding schedules, and supplementing diets with antioxidants. These interventions aim to mitigate the negative effects of heat stress on performance and welfare. However, the level of adoption and effectiveness of these measures vary widely across production systems.

Therefore, this study investigates the impact of heat stress on the growth performance and reproductive efficiency of broiler chickens, with the goal of identifying effective strategies for adaptation and management in hot environments.

1.2 Statement of the Problem

In recent years, poultry farmers have reported significant declines in broiler performance during periods of high temperature. Reduced feed intake, stunted growth, poor carcass quality, and low fertility rates have become common challenges. These problems are more pronounced in regions where electricity and cooling systems are inadequate.

Despite numerous studies on poultry management, limited research has focused on the combined effects of heat stress on both growth and reproduction under local tropical conditions. As a result, farmers often rely on trial-and-error methods rather than evidence-based strategies to mitigate heat-related losses. This knowledge gap has led to reduced productivity, higher operational costs, and economic instability in the poultry industry.

Hence, there is a need to conduct a systematic assessment of how heat stress influences the physiological, productive, and reproductive responses of broiler chickens. The findings will provide practical solutions for improving poultry resilience and performance in hot climates.

1.3 Objectives of the Study

The main objective of this study is to assess the impact of heat stress on the growth performance and reproductive efficiency of broiler chickens.

The specific objectives are to:

1. Determine the effect of heat stress on feed intake, weight gain, and feed conversion ratio in broilers.

2. Examine the influence of high temperature on fertility, hatchability, and reproductive hormones in broiler chickens.

3. Identify management strategies that can mitigate the adverse effects of heat stress on broiler performance.

1.4 Research Questions

The study will be guided by the following research questions:

1. How does heat stress affect the growth performance of broiler chickens?

2. What are the effects of elevated temperature on the reproductive efficiency of broilers?

3. Which adaptive or management strategies can reduce the impact of heat stress in poultry production?

1.5 Research Hypotheses

The study will test the following null hypotheses:

H₀₁: Heat stress has no significant effect on the growth performance of broiler chickens.
H₀₂: Heat stress does not significantly influence the reproductive efficiency of broiler chickens.

1.6 Significance of the Study

This study is significant because it contributes to the growing body of knowledge on poultry physiology and environmental adaptation. The results will help poultry farmers understand how temperature variations affect broiler productivity. It will also assist in developing practical management strategies that minimize production losses during hot seasons.

For animal scientists and researchers, the findings will provide a scientific basis for breeding programs that focus on heat-tolerant poultry strains. Policymakers may also use the information to design agricultural policies that support sustainable poultry farming under changing climate conditions.

1.7 Scope of the Study

The study focuses on evaluating the effects of heat stress on the growth and reproductive performance of broiler chickens. It will involve monitoring physiological responses such as feed intake, weight gain, and fertility rate under controlled environmental conditions. The study will be conducted in a tropical region where high ambient temperatures are common throughout the year.

1.8 Definition of Terms

• Heat Stress: A physiological condition that occurs when an animal’s heat load exceeds its capacity to dissipate heat.

• Growth Performance: Refers to measurable parameters such as feed intake, body weight gain, and feed conversion efficiency.

• Reproductive Efficiency: The ability of animals to reproduce successfully, including fertility, hatchability, and reproductive hormone balance.

• Broiler Chickens: A type of poultry breed specifically raised for meat production.