Mitigation measures of heat stress in farmed broilers

Pay attention to drinking water management during heat stress, the amount of chicken drinking is an extremely important factor. During heat stress, more than 80% of the heat production of chickens is emitted by evaporation. Studies have shown that the increase in the amount of drinking water is beneficial to the survival of chickens.

Increasing the intake of water containing sodium chloride or decreasing the water temperature can reduce the effect of heat stress. There is obvious complementarity between the addition of salt in drinking water and the temperature of drinking water. When the temperature of drinking water is lower than the body temperature of chickens, the addition of sodium chloride to drinking water can significantly increase the amount of drinking water and growth rate; when the water temperature is close to the body temperature of chickens, the addition of sodium chloride in drinking water has little effect on chickens. Lowering the water temperature without adding sodium chloride can also increase the amount of drinking water of chickens; if the water temperature is reduced while adding sodium chloride, it has a superposition effect on reducing the heat stress of broilers.

Before the advent of midsummer, the flock can be sparse according to the mode of feeding, combined with flock, elimination and so on, and the appropriate number of caged chickens and feeding density can be arranged. the flock of flat-raised chickens is not easy to be too large, and activities such as herding, beak breaking and transportation should be avoided as far as possible. If necessary, it should also be carried out on cloudy days or when the weather is cool in the morning and evening.

To increase ventilation in the house and reduce solar radiation on the buildings of the chicken house, it is necessary to consider using materials with good thermal insulation, which can be hung into ceilings with fibreboard, walls painted white, and trees and lawns planted around the chicken cottage. these measures are helpful to reduce the external radiation heat into the chicken house. The modern chicken farm is highly intensive. Ventilation and cooling in the house is an important part of preventing heat stress in broilers. The simplest way is to install fans in the chicken house. When the ambient temperature is lower than 40 ℃, increasing the wind speed is beneficial to the heat emission of chickens. In recent years, longitudinal ventilation has become an effective means to reduce heat stress, through continuous air exchange to keep the air fresh in the house. However, when the temperature is more than 30 ℃, the heat stress can not be controlled by longitudinal ventilation alone, and a wet curtain cooling device must be added to effectively reduce the heat stress. Recently, it is widely used to install a water curtain at the air entrance as a humidifier. In addition, using water or spray atomization devices on the roof of the chicken house can increase the evaporative heat dissipation of the roof and ease the heat transfer of the roof to the house.

Reasonable adjustment of nutrition level ⑴ dietary protein and amino acid content: reduce dietary protein content, but maintain the addition level of essential amino acids can improve the growth rate and survival rate of broilers. Corn-soybean-based diets need to be supplemented with methionine to obtain better broiler performance. Adjustment of ⑵ energy concentration: the adjustment of energy concentration in diet should be based on the principle of minimizing the production of increased heat consumption. Fat is a nutrient with the lowest heat consumption. Properly adjust the proportion of essential fatty acids in feed and use fat to replace part of carbohydrates in order to increase the energy concentration of feed and improve the adaptability of broilers during heat stress. ⑶ mineral addition: during heat stress, the excretion of potassium, sodium, zinc and molybdenum in urine increased, the excretion of calcium, manganese, selenium and copper in feces also increased, and the storage of magnesium and phosphorus also decreased. It can be added in time according to the need to meet the needs of the body.

Vitamin C supplementation with anti-stress additive ⑴: vitamin C supplementation during stress can significantly inhibit the increase of body temperature, increase feed intake and reduce the adverse effects of heat stress on metabolism. Vitamin C can be supplemented by feed or drinking water. ⑵ supplemented with vitamin E: hens suffering from chronic heat stress were fed diets with appropriate amount of vitamin E for one week, which could significantly inhibit the decrease of egg production during stress and make egg production return to normal as soon as possible. ⑶ added electrolyte: under the condition of heat stress, broilers are prone to respiratory alkalosis and hypokalemia, resulting in electrolyte balance disorder and affecting the regulatory activities of the body. Adding electrolytes to drinking water or feed can alleviate the harm caused by heat stress.