layer farming

Heat Stress Treatment in Poultry by Common Kitchen Herbal Ingredients

May 20, 2023

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Heat Stress Treatment in Poultry by Common Kitchen Herbal Ingredients

Heat stress is of great concern in all types of poultry production. Poultry production is associated with a range of stressors including environmental, nutritional, and biological, and such stress factors inevitably influence the animal’s physiology and performance with varying degrees.

HEAT STRESS
High ambient temperature is one of the most common stressors in commercial poultry production, resulting in reduced feed intake and body weight gain, and increased mortality. Because of their physiological state and greater metabolic activity, broilers are more susceptible to temperature-associated environmental challenges.

It also causes alterations in intestinal nutrient transporters, gut permeability and function, immune response and the endocrine system including cortisol and thyroid hormones. Moreover, elevated ambient temperatures have been reported to cause undesirable changes in carcass characteristics, bone mineralization, and meat quality.

Exposure to high ambient temperature elevates the level of reactive oxygen species (ROS) and causes biological and physiological disturbances in cellular functions. An uncontrolled increase in ROS level leads to free radical mediated chain reactions, which further causes lipid peroxidation and oxidative damage to proteins, DNA, and RNA. Birds respond to such conditions by reprograming several defense mechanisms including antioxidant enzymes, heat-shock proteins, and cytokines to alleviate or reduce the negative effects of Heat Stress.

Environmental and nutritional strategies are available to improve the efficiency of these defense mechanisms. Among the strategies for coping with the impact of HS in animals, dietary interventions through supplementation of several feed additives including vitamins (e.g. A, E and C) and minerals (e.g. zinc, selenium) can be utilized to improve the host’s antioxidant defense mechanism.

Vitamin E is a biological antioxidant and a free radical scavenger that protects the cells and lipid rich-membranes from oxidative damage and is considered as the core of the antioxidant system. Among the four tocopherols and four tocotrienols (designated as α-, β-, γ-, and δ-), only the α-tocopherol form has the biological activity to meet the animal’s Vit E requirements. Dietary supplementation of various levels of Vit E can improve broiler performance and reduce the oxidative stress experienced under high environmental temperatures.

Several studies have shown a positive effect of n-3 on bone mineral density (BMD) and bone mineral content (BMC) in animals.

Zinc is used in poultry diets because of its antistress effects. Moreover, its requirement increases and its retention decreases during stress. Zinc deficiency also causes shortness and thickness in long bones of legs and wings. There is also some evidence suggesting supplemental Zinc can alleviate negative effects of heat stress in broiler chickens.

Bone breaking strength is measured by evaluating the reaction of the bone to stress and force. An increase in bone mineralization is accompanied by an increase in bone stress and bending moment values. Bone mechanical strength is affected by nutrition, genes, age, sex, environment and etc., for the expression of collagen and proteins, quantity and quality of the organic and inorganic material, content and size of the mineral material, and design and structure of the bone (Boskey et al., 1999). Velleman (2000) explained the structural complexity and composition of bone associated with strength, which varied according to the age and nutritional status of the bird: femur compression strength = 11.9 + 0.0141 (bird BW).

However, contradictory data regarding the effect of vitamin E on collagen synthesis exists, and few studies have reported its influence on cartilage development. In fact, increasing in thickness of the growth plate was proportional to DL-α-tocopheryl acetate dose. The effect of vitamin E on chondrocytes was observed by Xu et al. (1995) in chicks fed by two levels of DL-α-tocopheryl acetate and two dietary lipids. The thickness of the entire growth plate cartilage and of the lower hypertrophic chondrocyte (mineralized) zone was significantly wider in animals fed the greater level of vitamin E. α-tocopherol protects PUFA from lipid oxidation. However, the effect of α-tocopherol and zinc supplementation on bone strengthen in poultry has rarely been studied and is rather controversial. The relation between dietary fat, zinc and vitamin E with heat stress on femur breaking strength has been studied separately.

Heat stress is a condition in chickens caused by high temperatures, especially when combined with high relative humidity and low airspeed. Heat stress occurs when the bird’s core body temperature increases to fatal temperatures because of poor heat loss and limited coping means. Older birds, heavy breeds, and broilers are often more susceptible to heat stress. It is the most important cause of mortality in summers leading to a huge economic loss.

Studies indicate that heat stress begins when the ambient temperature rises above 26.7°C and becomes very apparent above 29.4°C. Above 43.3°C , the bird is in danger of death.

Mechanism of heat dissipation/Thermoregulation

Since birds lack sweat glands and have a thick layer of feathers, it is difficult for them to regulate their body temperature.

The main process for birds to thermo-regulate when subjected to high temperatures is panting.

Panting is the first sign of increasing temperatures, birds begin to cool their air sacs by contact with the air and the humidity in the bags. As the frequency of panting increases, chances of dehydration increase too. Other methods to dissipate heat are opening of feathers to expose more skin surface and increased water consumption to increase the moisture content in the feces.

Effects of Heat Stress on Poultry

Severe heat stress can cause declines in egg production and growth rate. As high ambient temperature induces stress in birds, there is an expenditure of energy, which results in a reduction in the productive efficiency of the bird.
Decreased hatchability
Change in the quality of the egg: You may notice smaller eggs, thinner layers, and generally poor internal egg quality. Panting leads to decreased blood carbon dioxide (CO2) levels and increased blood pH, which hampers blood bicarbonate (HCO3-) and calcium (Ca) availability for eggshell mineralization. Also due to reduced feed intake, the hens consume less calcium and the levels of calcium in the blood drop; therefore the calcification of the egg is lower.

Heat stress also leads to decreased resistance and increases the risks of infectious diseases
Higher mortality rates in the flock

Heat stress is best diagnosed by Post Mortem findings which will reveal “slow-cooked meat” appearance or change in the muscles to pale or white colour.

Simple Management Solutions to Heat Stress Problem

Here are some tips on how to manage heat stress in chickens in the hot season:

External provisions such as fans, mist fans , sprinklers, housing with proper ventilation and appropriate ceiling height.
Managing Feeding: Most often, birds are hungriest in the morning and will tend to fill up. This will make them more prone to heat stress in the afternoon. Withdrawing feed birds six hours before peak warm temperatures in the afternoon can lower the risk of heat stress. Birds can then feed during night time hours when we expect cooler temperatures to occur. You can use lighting during night time (midnight) feeding to allow intake.
Reduce the dietary energy level in feed. Reduced protein:energy ratio.
Vitamin C supplementation: Ascorbic Acid (Vit. C) is one of the most important vitamins in heat stress. It inhibits the increase in the body temperature of birds, increases food intake, and promotes the recovery of damaged tissue cells. The high temperature inhibits the synthesis of vitamin C in layers and requires additional compensation.
Electrolyte therapy: Birds do not have sweat glands, so they cool off by panting. Panting can be a sign of heat stress and the act of panting can upset the electrolyte balance of birds. Electrolytes such as K, Na , P , Mg and Zn should be used to correct electrolyte imbalance due to heat stress
Prevent overcrowding: One of the best ways to prevent heat stress is to avoid overpopulation. To instantly reduce heat, reduce the number of birds in the house.
Avoid unnecessary activity: The summer heat puts enough stress on the birds. Be careful not to disturb them during the hottest time of the day.
Sodium bicarbonate supplementation: Soda bicarb in the feed is especially useful for hens in egg production. Due to panting, there is excessive loss of CO2. This release of CO2 changes the acid-base balance in poultry due to which there is reduction in availability of Bicarbonate (HCO3-) for egg shell formation. Thus supplementation of sodium bicarbonate can help lessen these changes.
Managing water: During heat stress, birds will increase their water intake by 2 to 4 times their normal intake. Sufficient water space, operating waterers and cool water temperatures will encourage the birds to drink. Flush water lines and waterers routinely to keep the water fresh and cool.
Use of Osmolytes: Addition of osmolytes like betaine in feed increase water holding capacity of cells in the body which prevents dehydration and improves water intake.