Heat Stress in Laying Hens: Effects and Mitigation
Poultry industry is an important sector of livestock production and plays an important role in economic growth. Rising consumption and production of poultry products, can have negative impacts on the productivity and health of chickens thereby affecting nutrition of humans due to various stressors which also includes abiotic factors. Over the years, long term single-trait selection for yields has resulted in modern poultry genotypes with greater metabolic activity, producing more body heat and lower heat tolerance. The birds when exposed to heat stress leads to alteration in behavioural, physiological and immunological responses which causes unfavourable effect on their overall productivity, and is much more pronounced during hot seasons. The losses due to heat stress in broilers include high mortality, diminished growth, reduced egg production, deterioration in meat and egg quality and safety.
Heat stress impairs the performance, productivity and health of the birds by reducing feed intake, decreasing nutrient utilization, disrupting intestinal structure and compromising the immune systems. It results from a negative balance between the net amount of energy flowing from the bird’s body to its surrounding environment and the amount of heat energy produced by the bird. The issue of environmental stress is now quickly becoming a great point of interest in animal agriculture, particularly due to public awareness and concerns.
Heat stress can have a significant influence on laying hens, so it’s critical to understand what it does and how to avoid it. The poultry sector has grown quickly during the past few decades. Improvements in the genetic selection of the many breeds of laying hens have supported this evolution. Additionally, there have been notable advancements in management, management welfare, and nutrition. In order to meet the significant feed demand around the world, poultry farming has been able to combine all of these operations and optimize them. Due to the warm weather, poultry is vulnerable to heat stress, also known as summer stress, throughout the summer. This happens when the body’s heat production and loss are out of balance. In addition to affecting bird performance, this condition causes significant economic losses due to poor growth, decreased production and an increase in mortality. To prevent heat exhaustion in laying hens There are many ways to manage heat stress in hens, including appropriate curtain management, modifying the water and feed offered and modifying the ventilation system. To prevent heat stress and strengthen chickens’ immune systems, some solutions also provide vitamins, minerals and immunostimulants.
Importance of heat stress in poultry farming
The rate of development of producing poultry has accelerated both throughout the juvenile and production stages. The physiology of this poultry has changed as a result of an increase in metabolic rate necessary for quick development and a more productive stage. A quick metabolism, on the other hand, suggests that nutrients are quickly metabolized. These metabolic activities produce heat, which the chickens are unable to effectively expel. The first is radiation, where the body radiates heat into the environment, but the feather covering reduces this. There are also less effective ways for the poultry to shed heat. Second, by conduction when coming into contact with cool surfaces, however confined laying hens lack this effective route of heat removal. Thirdly, using convection, which relies on a productive ventilation system in the home, heat is transferred to the air that is flowing. The efficiency of evaporation by respiration, our final option, relies on the humidity of the surrounding air. These factors make chickens prone to heat stress, which is bad for the wellbeing of the animals.
Heat stress effects on laying hens
According to their degree and duration, acute and chronic heat stress that affects production poultry can be broadly categorized into two categories. Acute heat stress is characterized by a rapid increase in temperature, which causes the fowl to exhibit acute symptoms. On the other hand, chronic heat stress is defined as a continuous and sustained state of heat stress that affects chickens with varying degrees of severity. This poultry issue affects chicken functionality and physiology in a number of ways, as discussed below.
Performance and nutrition for productivity
According to studies on chicken husbandry, heat stress in laying hens reduces body weight, egg production, egg weight, and eggshell quality. Additionally, poultry under heat stress consumes less feed. Chronic heat stress has been reported to dramatically lower dietary protein intake and have an impact on feed digestion, particularly for lipids and proteins. The health and productivity of the chickens are subsequently impaired.
Mineral homeostasis
Animals like laying chickens need the right mineral balance to ensure the laying stage, particularly minerals like calcium. However, it is noted that the acid-base balance is disturbed during acute heat stress, which hinders calcium absorption at the duodenum level. Heat speeds up the poultry’s respiratory rate, which causes a significant CO2 exhalation and causes respiratory alkalosis. According to reports, in this condition, the amount of plasma-available ionic calcium, which is necessary for the production of the eggshell and affects both its quality and thickness, is decreased. This ionic imbalance also increases the risk of skeletal system degradation.
System of defense
The immune system is impacted by heat stress in chicken husbandry, according to research. It has been discovered that this issue has an impact on young poultry’s particular immunity, suppressing white blood cells and elevating the heterophile/lymphocyte ratio (stress indicator). In addition, it has been discovered that under specific circumstances, heat stress in laying hens might lower the quantity of antibodies generated. Production poultry are more likely to have significant morbidity and mortality rates in cases of infectious diseases due to their decreased immunity. Since effective immunization is not obtained, it may even disrupt the vaccination process.
Mortality
According to studies on heat stress in poultry, this condition greatly raises the percentage of deaths from acute asphyxia and chronic immunosuppression in the species.
Physiology of reproduction
The system in charge of egg development in chickens is the reproductive system. Due to the oxidative stress that heat stress puts the ovarian follicles under, its functionality is affected. On the other hand, it has been discovered to enhance chemicals that cause liver cells to apoptose with severity comparable to mycotoxins.
Control measures for heat stress
Poultry houses are distinguished by a high animal density inside the building. If adequate management conditions are not established, this large number of animals raises the temperature within the house. To combat heat stress in poultry, there are methods on many fronts.
Curtain Regulation
By managing the curtains, poultry houses may improve the temperature and humidity levels. The chicken house’s inside is cooled and made less warm by outside air in this manner. To properly balance these elements, however, temperature and humidity metres should be present. Animal welfare and productivity are enhanced when chickens are kept in a safe and comfortable setting.
Ventilation Strategies
Poultry buildings that are large or have a lot of birds inside need have a reliable ventilation system to maintain a controlled environment. Additionally, they lessen the likelihood of issues caused by humidity, ammonia, and heat stress. To consistently assure their operation, it is advised to examine the effectiveness of exhaust fans and fans on a regular basis.
Food and Water
If the poultry coop is generating heat, the temperature of the water that is available for consumption may rise. Because it causes them to drink less water and experience more stress, this has a negative impact on the health of the fowl. As a result, the water temperature should be kept cool and regularly checked in relation to the outside temperature. On the other hand, the feed ratio can be altered in tropical regions or places with high ambient temperatures. To lower the poultry’s metabolic rate and prevent a state of heat stress, the diet’s protein, carbohydrate, and fat content can be changed.
Supplementing with vitamins and minerals
Supplements for vitamins and minerals can be given to poultry, such as Alquerfeed Ovoponedoras, which improves the quality of the eggshell. This product helps laying hens produce eggs more efficiently, particularly when they are under heat stress. As a result, it reduces the availability of calcium for ideal physiology and inhibits bone demineralization.
Immunostimulants
Immunosuppressive conditions brought on by heat stress can be avoided thanks to the immunostimulants included in the diet. Both in young and adult poultry, Alquernat Inmuplus improves both the specific and non-specific immune system. As a result, the reaction to vaccination is improved, which also helps to improve the poultry house’s immunity to infectious diseases. Conclusion Genetic selection has been used to improve the productivity and efficiency of laying hens. In addition, their production has benefited from notable advancements in nutrition and welfare. The physiology of chickens, however, poses challenges to managing excessive heat. The high metabolic rate and inability to expel heat produced by poultry define them. Therefore, poultry farming experiences heat stress. Heat stress causes a variety of pathological changes in poultry, including decreased productivity in laying hens, which has an impact on the quality of their eggs. The mineral balance is also changed, and feed intake is decreased. The physiology of the reproductive system is impacted as well as the immunological system. There are multiple strategies to deal with heat stress in chickens, including proper curtain management, ventilation system adaptation and modification of the water and feed supplied. Finally, some solutions offer vitamins, minerals and immunostimulants to help chickens avoid heat stress and build their immune systems.
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
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HEAT STRESS IN COMMERCIAL POULTRY: SIGNS, EFFECTS AND MITIGATION STRATEGIES
