Heat stress and its mitigation measures in summer and autumn chickens

Effect of heat stress on broilers

1. Physiological and biochemical changes of broilers under heat stress. When the external ambient temperature increases, the chicken body temperature will increase with the increase of ambient temperature, when the heart rate increases, blood pressure decreases, breathing accelerates wheezing, and respiratory alkalosis occurs in severe cases. In addition, heat stress can also lead to endocrine disorders, adrenal corticosterone concentration significantly increased in the early stage of heat stress, but the prolonged stress time gradually decreased thyroxine secretion, decreased activity led to a decrease in metabolic rate.

2. Effect of heat stress on growth rate and feed intake of broilers. Generally, broilers can achieve better growth rate and feed conversion rate at the ambient temperature of 18 ℃ and 24 ℃. When the ambient temperature exceeds 26 ℃, the feed intake decreases and the growth rate begins to slow down. The experimental results show that when the ambient temperature is 21: 30 ℃, the feed intake decreases by 1.5% for every 1 ℃ increase; in the range of 32-38 ℃, when the ambient temperature increases by 1 ℃, the feed intake decreases by 4.6%.

3. Effect of heat stress on disease resistance of broilers. High temperature and humidity is the main condition for the mass reproduction of a variety of parasitic pathogens. Under heat stress, the immunity of broilers is suppressed, and chickens are easy to stimulate respiratory diseases and ulcerative enteritis, and are vulnerable to staphylococci, Escherichia coli and Pseudomonas aeruginosa, and are more susceptible to Newcastle disease, infectious laryngotracheitis and poultry.

Measures to relieve heat stress

1. Installation of ventilation and cooling equipment the suitable temperature for broilers is 18-24 ℃. Because the chicken has no sweat glands and feathers on the body surface, it mainly depends on breathing to reduce the temperature in the body. Install exhaust fans and ceiling fans in the chicken coop to lower the temperature in the body. It is best to use the pedestal floor fan if possible, because the pedestal ground fan can make the wind flow horizontally, take away the hot air and lower the temperature, which can reduce certain stress.

2. spray water to cool down in the hot noon, use the spray system to spray water directly around the chicken body and chicken house and on the roof, and take away part of the heat by evaporating water.

Install a water curtain install a water curtain at one end of the chicken house, install an exhaust fan at the other end, and then seal the window and rely on the water curtain to make it longitudinally ventilated, so as to make the cool air flow in the chicken house, thus reducing the temperature in the house.

4. Drink enough fresh cold water in general farms, most of which have a storage tank and bucket. In order to ensure the quality and coolness of the water, it is best to pump it now, not to draw too much at once, and try to let it finish in the shortest time, and then smoke it again. And there are plenty of drinking utensils.

5. plant trees to shade the chicken coop, do not build it too low, and sit north and face south as far as possible, plant trees properly before and after the henhouse to avoid direct sunlight on the henhouse. Or shade in front of the chicken coop to lower the temperature.

6. reduce the feeding density before the advent of summer, according to the feeding mode, combined with the transformation, merging and elimination of the group can be carried out once. Excessive density is not conducive to the emission of body heat and is easy to cause exhaustion.

7. To reduce extra stress in the hot summer, it is best to avoid the work of group conversion, group expansion and immunization at noon, and the feeding time should be adjusted to early morning, dusk and night. Conditional chicken farms had better try to limit their range of activities in a few small columns on the fence of the whole chicken house to reduce stress.

8. The roof and south wall are painted white with cement and lime milk to reduce heat absorption.

9. Install sprinkler belt or steel pipe in the chicken house and circulate with fresh cold water to lower the body temperature of the chicken.

10. Wet the feed with fresh well water and let it eat freely.

11. Adjust the feed formula. In the current common feed, the contents of protein, vitamins and minerals should be increased in proportion, and the full price feed with high energy and high amino acids which is easy to digest should be fed. For example, adding VC, VE, lysine and methionine to the diet, but also reducing the energy content in the feed to play the role of anti-stress.

12. Use anti-stress drugs. In summer, vitamins and minerals in feed are easily oxidized and denatured. In order to reduce heat stress, some stress prevention drugs and additives can be used to reduce heat stress. The main results are as follows: (1) when the body was supplemented with VC and heat stress, the synthesis ability of VC decreased, but the requirement of VC increased at this time. 0.02~0.04%VC was generally added to the diet, that is, 2kg / 10kg feed. (2) supplementation of oral rehydration salts can also play a role in anti-heat stress. (3) add ammonium chloride to diet or drinking water. Respiratory alkalosis occurs during heat stress in chickens, and the addition of ammonium chloride and its alkali neutralization can significantly reduce the blood PH value. (4) Sodium bicarbonate was added to the diet or drinking water, so sodium bicarbonate was added to the diet because the bicarbonate ion in chicken blood decreased during heat stress. Generally, 0.5% is added to the feed. Mixing ingredients is better than drinking water. (5) dietary supplementation of citric acid, aspirin and potassium chloride can also reduce heat stress.