After heat stress, both broiler and laying hens will have reduced performance or egg production. In the absence of funds to improve sanitary conditions or ventilation systems, the only thing that can be done is to change the composition or composition of the diet.
Higher ambient temperatures are an important factor in poultry stress and are also directly related to the profitability of poultry or egg production. There are seasonal problems in poultry production in many parts of the world, especially in tropical and subtropical regions. When the ambient temperature is 35-43 °C, the feed intake is reduced, the nutrient utilization rate is reduced, and the weight is reduced. Egg rate, egg quality and feed conversion efficiency are all reduced, resulting in economic losses. For broilers, the optimum temperature for weight gain is 10-22 ° C, and the optimum temperature for feed conversion efficiency is 15-27 ° C. Laying hens have the best egg production performance in an environment of 10-30 °C. Above 30 ° C, growth and egg yield will decline. Due to the lack of sweat glands and relatively high body temperature, poultry, especially meat-type fast-ripening varieties, are more sensitive to heat stress. When exposed to higher ambient temperatures, birds face difficulties in maintaining body temperature. When the temperature exceeds the critical temperature, the primary way to cool the birds is to increase the breathing rate (gasping) and flap the wings (increasing the surface area). Under stress, the blood of the birds changes from acid-base balance to alkaline balance. Vitamin C levels in the adrenal cortex decrease, lymphocytes decrease, and the immune response is also inhibited. As the ambient temperature increases, poultry will increase the amount of water, respiratory efficiency and body temperature also increase, egg quality decline, and the disease is more susceptible.
A variety of methods have been used to mitigate the negative impact of higher ambient temperatures on poultry production. In general, heat stress can be dealt with by controlling the temperature of the poultry environment, such as taking measures to cool down and ventilate. However, these methods are sometimes not very feasible, especially for some small-scale farms or free-range farmers, where ventilation cooling equipment often requires a certain investment, so other methods must be considered to deal with heat stress. The use of nutrition is one of the ways to meet the needs of stress-affected birds by changing the nutrient composition of the diet. Ambient temperature has a major impact on the feed consumption of poultry, especially adult poultry, as feed intake is reduced as the ambient temperature increases. Above 30 °C, the average intake of feed increased by 2.5-4 grams per degree. Therefore, higher density diets need to be fed to maintain dietary intake to meet growth and egg production needs. Reducing the amount of protein in the diet and increasing the amount of essential amino acids is also an effective way to cope with heat stress. Adding electrolytes (such as sodium, chlorine, potassium, sodium bicarbonate, etc.) to drinking water helps to replenish the electrolyte and correct the acid-base balance. The addition of antioxidant vitamins to diets is also an effective way to reduce heat stress. The main reason why antioxidant vitamins such as vitamin A (retinol), vitamin E (alpha-tocopherol) and vitamin C (ascorbic acid) are used in diets is that they have an anti-stress effect. At the same time, another important reason is that these vitamins synthesized by birds themselves after heat stress are reduced. Heat stress stimulates the release of corticosterone and catecholamines and initiates peroxidation of cell membrane lipids. It has been reported that heat stress can reduce the content of plasma ascorbic acid and alpha-tocopherol. Heat stress can also affect the absorption of these vitamins (A, E, and C), which in turn increases the body's need for these vitamins. The addition of these vitamins to the diet helps to cope with the decline in production performance caused by heat stress.
Vitamin E (Vitamin E)
Vitamin E is one of the important natural antioxidants and an important biochain antioxidant that protects cells and tissues from free radical-induced liposome peroxidation damage. Birds cannot synthesize vitamin E by themselves and therefore need to be obtained from the diet. Heat stress stimulates the release of corticosterone and catecholamines and initiates peroxidation of cell membrane lipids. This also means that vitamin E can reduce the negative effects of stress-releasing corticosterone. Vitamin E also protects against the antioxidant effects of cells involved in immune responses (such as lymphocytes, macrophages, and plasma cells), and also enhances the function of these cells to spread. Therefore, the addition of vitamin E to the diet is effective in combating heat stress. For broilers, the addition of vitamin E to the diet at 250 mg per kilogram can better alleviate the effects of heat stress, making the broiler in good growth. For laying hens, adding 125-250 mg of vitamin E per kilogram of diet can increase egg yield, feed conversion efficiency, and immune function. Heat stress can reduce the concentration of egg yolk precursor, egg yolk and very low density lipoprotein, resulting in a decline in egg production. Vitamin E can promote the release of egg yolk from the liver, enhance the function of egg yolk precursor formation by protecting liver lipids from peroxidation damage and cell membrane damage, thereby improving egg production.
Vitamin C ( C)
Vitamin C is required for various biosynthesis (such as collagen, 1,25-dihydroxyvitamin D and epinephrine) and various reactions (secretion of corticosteroids, regulation of body temperature, activation of the immune system, etc.). It has been reported that vitamin C can increase the antioxidant activity of vitamin E by reducing the active form of vitamin E by reducing tocopherol hydroxyl radicals. Adult chickens can synthesize vitamin C by themselves to meet the needs of the body. However, it has been reported that the amount of vitamin C required is increased when stressed. In addition, there have been reports that the addition of ascorbic acid in the feed has a good effect. Adding a certain amount of vitamin C to the diet can alleviate the symptoms of stress, improve production performance and immunity. For broilers, adding 250 mg of vitamin C per kilogram of diet can promote growth and improve feed conversion efficiency. For laying hens, adding 200-400 mg of vitamin C per kilogram of diet can improve egg production and egg quality.
Vitamin A ( A)
Vitamin A is involved in many functions of the body, including vision, epithelial cell differentiation, growth and proliferation. Since vitamin A is involved in epithelial cell differentiation, it plays an important role in the immune function of birds. It has been reported that the conversion of carotene to vitamin A can reduce stress. Dietary supplementation with vitamin A (15,000 IU/kg) and zinc (30 mg/kg) can improve the performance of broilers and the quality of ketone bodies, thus potentially preventing heat stress in broilers. When the laying hens are exposed to heat stress, supplementation with vitamin A (9000 IU/kg) in the diet can effectively promote growth and immunity.
Antioxidant vitamin
Antioxidant vitamin complexes have a more effective role in preventing the decline in production performance associated with heat stress. Mixing several different antioxidant vitamins tends to be much better than using only one alone. Studies have shown that in the summer when heat stress is prone to occur, adding vitamin C (200mg/kg) and vitamin E (125mg/kg) to the diet of Bailaihang chicken can effectively promote production and improve immune function. . Vitamin A (15,000 IU/kg) and vitamin E (250 mg/kg) in broiler diets can also effectively promote growth. At higher temperatures, food intake is reduced, vitamin absorption and digestibility are reduced, leading to a lack of specific nutrients. Therefore, in the summer, you need to increase the amount of vitamins to maintain normal production. Dietary vitamin E (125-250mg/kg), vitamin C (200-250mg/kg) and vitamin A (15000IU/kg) can effectively alleviate the effects of heat stress on poultry production.
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