For Poultry, they can completely adjust and adapt to through mild stress behavior for short-term and mild temperature changes (26-32 degrees); but Long-term and relatively large temperature increases (above 32 degrees) will cause the physiological function of poultry to be disordered, and growth retardation, which in turn, leads to a series of declines in production indicators (Feed intake, growth rate, carcass quality, egg fertilization rate, hatchability) decline, and even cause poultry failure and death, making producers unprofitable or even loss-making.
Physiological manifestations of heat stress
- Heat wheezing: Appropriate heat wheezing can increase the release of body heat, but excessive wheezing will lead to excessive CO2 excretion, CO2 partial pressure in the blood will drop, pH value will rise, and alkalosis will be induced; Central inhibition, excessive accumulation of H2CO3 in the body may lead to acidosis.
- Rapid heart rate: insufficient oxygen in the blood due to heat stress and heat wheezing (shallow breathing); rapid heart rate followed by heart failure, which can lead to venous return disorders, pulmonary blood stasis, edema, hypoxia and acidosis.
- The oxidation process in the body is intensified: the body temperature rises, the oxidative metabolism of the three major substances in the body is strengthened, the harmful metabolic intermediates and end products (endotoxins) increase, the cell lipid membrane is damaged by oxidation, the gap in the blood vessel wall is enlarged, and it is very easy to Causes hemorrhage, hemolysis, tissue damage and autotoxicity. Under the state of heat stress, the body's redox imbalance, and the accumulation of endogenously generated free radicals (mainly ROS) causes oxidative stress. In the state of oxidative stress, the function of the endoplasmic reticulum is altered, causing endoplasmic reticulum stress.
- Increased secretion of adrenal cortex hormones: in the initial stage, metabolism is enhanced, energy and protein consumption is increased, and the body is in a state of high tension. Later, the secretion of thyroxine and cortisol (anti-stress) decreases, gradually exhausts, and can cause lymphocyte nucleic acid. Dicer activity is increased, cellular immunity and humoral immunity are weakened; nerve excitability is increased or inhibited, etc.
- Heat stress reduces the expression of bile acid synthase and bile acid modification key enzymes in the liver, and affects the secretion and output of bile acid. Reducing the content of FXR and TGR5 in the liver is beneficial to the synthesis of TG and fat deposition, resulting in fat variability.
- Excessive excretion of feces and urine and watery stools: lead to the loss of potassium, sodium and various trace elements in the body, imbalance of electrolyte balance and dehydration
Comprehensive measures to relieve heat stress
Alleviating heat stress requires comprehensive treatment from multiple dimensions, which cannot be solved by one solution.
1. First, adjust the feeding mode according to the production status and the needs of chickens (the corn ration is converted into a multi-grain ration mode); implement measures to relieve stress (such as temperature control, welfare); sanitation management (such as dustproof, clean poultry Use of mycotoxin adsorbents and detoxifiers to remove endotoxins (bile acids); provide biological protection through the establishment of additives; protect the liver and strengthen the liver, improve intestinal permeability; reduce or eradicate subclinical antibiotics use.
2. Provide appropriate ventilation according to the number of chickens in the poultry house; adjust the fan position, optimize the wind speed, and promote air circulation; reduce the stocking density; do a good job of insulation facilities in the house to avoid solar heat accumulation; use evaporative cooling pads or atomizing nozzles; Maintain water and electrolyte balance, supplement vitamins; use plant extracts, essential oil feed additives to relieve and reduce the effects of heat stress.
3. Commonly used anti-stress additives, "treating the symptoms but not the root cause"
① Supplement electrolytes such as sodium bicarbonate, ammonium chloride, potassium chloride, etc. to relieve acidosis and maintain electrolyte balance.
② Supplement vitamins (such as vitamin C, and E), and trace elements (zinc, selenium, chromium) to enhance antioxidant capacity.
③Add Chinese herbal medicines, extracts, essential oils, amino acids, organic acids, etc.
4. Add bile acids to relieve heat stress and fundamentally control endoplasmic reticulum oxidative stress
①In heat stress environment, adding bile acid can effectively improve the utilization rate of oil, reduce body heat gain, and relieve heat stress.
②In the heat stress environment, reduce the protein concentration, increase the amino acid level (especially methionine), add bile acid, improve the protein utilization rate, and relieve the body burden caused by heat stress.
③Bile acids are added to the feed to combine and excrete endotoxins, accelerate the metabolism of mycotoxins, reduce oxidative stressors, and relieve oxidative stress in the endoplasmic reticulum.
④ Adding bile acids to feed can increase the activity of antioxidant enzymes (SOD, GPH-x), reduce the content of malondialdehyde (MDA), increase the level of antioxidant (TAOC), and relieve heat stress.
Conclusion
In a word, to alleviate the heat stress of poultry, first of all, it is necessary to improve the environment and cut off the environmental stressors as much as possible; secondly, to improve the digestibility of feed and reduce the burden on the intestines; to remove toxins again to reduce the oxidative stressors; finally, to improve the body’s antioxidant capacity and reduce the Endoplasmic reticulum stress relieves the adverse physiological performance caused by heat stress and ensures the normal production performance of poultry.
