How to Handle Heat Stress in Chickens? Detailed Relief Measures for Summer and Autumn

Effects of Heat Stress on Broiler Chickens

1. Physiological and biochemical changes in broiler chickens under heat stress. When the ambient temperature rises, the body temperature of chickens rises along with the ambient temperature; at this point the heart rate speeds up, blood pressure drops, breathing accelerates and panting occurs, and in severe cases respiratory alkalosis develops. In addition, heat stress can also cause endocrine disorders: the adrenal corticosterone concentration increases significantly in the early stage of heat stress, but gradually declines as the stress period is prolonged; thyroxine secretion decreases, and the decline in its activity leads to a lower metabolic rate.

2. Effects of heat stress on the growth rate and feed intake of broiler chickens. Generally, broiler chickens raised at an ambient temperature of 18-24°C can achieve a better growth rate and better feed conversion ratio; when the ambient temperature exceeds 26°C, the feed intake of broiler chickens decreases and the growth rate begins to slow down. Experiments have shown that at an ambient temperature of 21-30°C, feed intake drops by 1.5% for every 1°C increase; within the range of 32-38°C, feed intake drops by 4.6% for every 1°C increase in ambient temperature.

3. Effects of heat stress on the disease resistance of broiler chickens. High temperature and high humidity are the main conditions that cause the massive proliferation of various parasites and pathogenic bacteria. Under heat stress, the immune capacity of broiler chickens is suppressed, and the chicken body is prone to respiratory diseases, ulcerative enteritis, etc., and is susceptible to invasion by Staphylococcus, Escherichia coli and Pseudomonas aeruginosa, with increased susceptibility to Newcastle disease, infectious laryngotracheitis and fowl cholera.

Measures to Relieve Heat Stress

1. Install ventilation and cooling equipment. Generally, the suitable temperature for broiler chickens is 18-24°C. Since chickens have no sweat glands and have feathers on the body surface, they mainly rely on breathing to lower their body temperature. Install exhaust fans and ceiling fans in the chicken house to lower the body temperature. If conditions permit, it is best to use floor fans, because floor fans can make the air flow horizontally, carrying away hot air and lowering the temperature, which can reduce stress to a certain extent.

2. Spray water for cooling. At the hot noon, use a spray system to spray clean water directly on the chicken bodies, around the chicken house and on the roof, relying on water evaporation to carry away part of the heat.

3. Install a water curtain. Install a water curtain at one end of the chicken house and an exhaust fan at the other end, then seal the windows, and rely on the water curtain to create longitudinal ventilation, so that cool air flows through the chicken house, thereby lowering the temperature inside the house.

4. Provide enough fresh cool water. In most farms, there is usually a water storage tank and buckets. To ensure the quality and coolness of the water, it is best to pump it just before use; do not pump too much at one time. Try to let the chickens finish drinking it in the shortest possible time, then pump again, and there must also be sufficient drinking water utensils.

5. Plant trees for shade. The chicken house should not be built too low, and should face south as much as possible; plant trees appropriately in front of and behind the chicken house to avoid direct sunlight on the chicken house. Alternatively, provide shade in front of the chicken house to lower the temperature.

6. Reduce stocking density. Before midsummer arrives, according to the rearing method, carry out a thinning of the flock in combination with regrouping, merging groups and culling. Excessive density is not conducive to the dissipation of body heat and easily causes exhaustion.

7. Reduce extra stress. In the hot summer, it is best to avoid carrying out regrouping, flock expansion and immunization at noon, and the feeding time should be adjusted to early morning, dusk or night for the best results. If conditions permit, chicken farms should try to set up several small pens within the whole chicken house to limit their range of activity and reduce stress.

8. Paint the roof and south wall white with cement and lime milk to reduce heat absorption.

9. Install sprinkler belts or steel pipes in the chicken house and circulate fresh cool water through them, letting the chickens lie on them to lower their body temperature.

10. Moisten the feed with fresh well water and let the chickens eat freely.

11. Adjust the feed formula. In the currently common feed, appropriately increase the proportions of protein, vitamins and minerals, and feed an easily digestible complete feed with high energy and high amino acids. For example: supplement the diet with VC, VE, lysine, methionine, etc., and also reduce the energy content in the feed to play an anti-stress role.

12. Use anti-stress drugs. In summer, the vitamins and minerals in feed are very easily oxidized, denatured and invalidated. To reduce heat stress, chickens can be given some stress-prevention drugs and additives that alleviate heat stress for adjustment. (1) Supplement VC in the diet. Under heat stress, the body's ability to synthesize VC declines, while the requirement for VC increases at this time. Generally, add 0.02-0.04% VC to the diet, that is, add 2-4 grams to 10 kg of feed. (2) Supplementing oral rehydration salts can also play an anti-heat-stress role. (3) Add ammonium chloride to the diet or drinking water. When chickens suffer heat stress, respiratory alkalosis occurs; adding ammonium chloride at this time neutralizes the alkali and can significantly lower blood pH. (4) Add sodium bicarbonate to the diet or drinking water. Since under heat stress the bicarbonate ions in chicken blood decrease, sodium bicarbonate is added to the diet. Generally, supplement 0.5% in the feed. (Mixing into feed works better than adding to drinking water.) (5) Supplementing the diet with citric acid, aspirin, potassium chloride, etc. can also play a role in reducing heat stress.