Clinical manifestations, prevention and treatment of heat stress in chickens

(1) the tolerance of chickens to heat. Because chickens have physiological characteristics such as high body temperature, exuberant metabolism and no sweat glands, the ability to tolerate high temperature environment is low, so high temperature has become the most harmful stress factor in chicken stressors. According to relevant measurements, the best digestion temperature for laying hens raised in China is 21-24 ℃, the best laying temperature is 15-20 ℃, and the relative humidity is 60% Mel 65%. When the egg production was above 28 ℃, the egg production decreased, and 1 ℃ per liter, the heat dissipation decreased, the food intake decreased by 1.6%, and at about 30 ℃, the egg production decreased by 3% Mel 4%, and asthma occurred. The physiological regulation of temperature in chickens can reach 32 ℃. At 35 ℃, physiological regulation was inhibited, and symptoms such as elevated body temperature, severe heat asthma, fainting and even death occurred.

(2) Monitoring of heat stress in chickens. At present, there is no monitoring standard in China, but in terms of the physiological and biochemical effects of high temperature on chickens, there are the following aspects.

1. Clinical manifestation. Phenomena such as reduced or refused feeding, increased drinking water, heat asthma, mental tension or depression, decreased egg production, less and dry feces with blood, chicken crown cyanosis (some pale) and so on.

2. Blood changes. Blood glucose, blood lipid and total protein decreased significantly. The partial pressure of oxygen is decreasing and the partial pressure of carbon dioxide is increasing. Serum potassium decreased and serum sodium increased. The activity of ML phosphokinase in serum increased sharply, the activity of glutamic pyruvic transaminase and lactate dehydrogenase decreased significantly, and vitamin C decreased. Plasma aldosterone increased, which was consistent with the changes of serum potassium and sodium. Estradiol, corticosterone and thyroid hormone decreased.

3. Autopsy. Muscle pale, soft as mud, boiled changes; myocardial dilatation, with large bleeding; intestinal catarrhal inflammation; cloacal mucosa with congestion, bleeding and edema and so on.

(3) Prevention and treatment of heat stress. When the temperature exceeds 32 ℃ and below 35 ℃, it has a great impact on production. When the temperature exceeds 35 ℃, individual chickens will die. Therefore, different countermeasures are taken according to the temperature in different houses.

1. When the temperature in the house reaches 30-35 ℃, 0.2% sodium bicarbonate or 150-300g vitamin C150-300g should be added to the feed. If the amount of sodium bicarbonate is increased, the amount of sodium chloride in the feed should be reduced accordingly. Due to the high temperature, the demand for vitamins in chickens is generally 2 times higher than normal, so it is particularly important to supplement adequate vitamins in summer.

2. When the temperature in the house is higher than 35 ℃, the dead chicken will appear in the flock. The higher the temperature is, the more serious the chicken death will be. Its prevention and cure uses an Nai nearly 10 grams to mix water 50 kilograms, drink throughout the day, the effect is excellent.