Causes and preventive measures of broiler lung injury

Broiler lung injury is a serious respiratory disease, usually caused by the interaction of multiple pathogenic infections, environmental stress and many other factors. The high mortality rate brings huge economic losses to the poultry farming industry. Therefore, understanding the cause of broiler lung injury and taking effective measures to prevent it is the top priority of the current broiler farming industry.

1. Causes of broiler lung injury The

lung is a gas exchange organ. After the bronchus enters the lungs, it does not branch step by step to form a bronchial tree as in mammals, but forms interconnected tubes, and finally separates countless tiny pulmonary capillaries (also known as respiratory capillaries) from the tube wall, which are connected with the pulmonary blood vessels. The place where the blood directly exchanges gases.

Calculated per gram of body weight, the total respiratory area of the pulmonary capillary is dozens of times larger than that of mammals, which is compatible with the strong metabolic needs in the body. Chicken lungs can also perform double respiration, that is, gas exchange can be performed when inhaling and exhaling, thereby greatly increasing the ventilation volume of the lungs and improving the efficiency of gas exchange in the lungs. The air sac is a unique organ of poultry. It is a membranous sac formed after the branch of the bronchus leaves the lung, and most of it communicates with the lumen of many bones.

The lungs have an important impact on the physiological activities of chickens and are also the most vulnerable organs. Common lung injuries are generally caused by the following reasons.

1. Environmental factors

1.1 Temperature

1. At low temperature, cold air stimulates the respiratory mucosa and lung tissue, causing local vasoconstriction and circulatory disturbance, resulting in local nutritional deficiency, weakening or stopping of ciliated epithelial activity, increased tissue protein decomposition, and large Molecular colloid protein increases accordingly, and the activity of reticuloendothelial system weakens. The barrier function is damaged, the body's ability to resist infection is reduced, the respiratory mucosa is easily invaded by pathogenic microorganisms and spread to the lungs to cause lung infection, or the formation of new alveoli slows down, and abnormal gas exchange (oxygen, carbon dioxide) causes pulmonary hypertension, causing lung damage.

2. When the temperature is high, the first reason is that the chicken will breathe faster to dissipate heat, and the number of breaths will increase, which will lead to blood vessel congestion in the respiratory tract mucosa. Over time, due to the expansion of blood vessels, exudative inflammation will easily occur, and the cilia will easily fall off, exposing the mucous membrane, causing damage, and easily Infection with pathogenic microorganisms promotes the formation of pneumonia. Pulmonary congestion-congestion edema occurs. The second is that the heart rate increases at high temperature, shallow breathing leads to insufficient oxygen in the blood, the compensatory acceleration of the heart rate, and heart failure after the tachycardia can lead to venous blood return obstruction, pulmonary congestion, edema, and hypoxia in the body.

1.2 Humidity

1. Humidity is too high: if the humidity is greater than 70%, it will affect the body heat dissipation of the big chickens, and speed up breathing for heat dissipation to promote breathing and heat dissipation. High humidity increases the intrapulmonary pressure and causes congestion of the respiratory organs. Over a long period of time, pulmonary congestion-congestion-edema will occur, and lung consolidation will cause pneumonia.

2. Humidity is too low: the humidity is less than 30%, the air is dry, and there is a lot of dust (fine feathers, dust, powder, etc.). After inhalation, it enters the respiratory system with the air. Attached, too much will cause obstruction and poor breathing. If the number of microorganisms attached is large, it is also easy to cause respiratory infection or lung infection.

1.3 Negative pressure

The negative pressure of standardized chicken houses for broilers is required to be within -0.08 Mpa, and if the negative pressure exceeds -0.08 Mpa, it will cause a certain degree of damage to the lungs. When the negative pressure exceeds the standard, the back wind speed in the chicken house exceeds the normal standard, the amount of oxygen discharged from the chicken house increases, and the amount of oxygen entering the chicken house from the air inlet is not enough to replenish the oxygen to the normal value required by the chickens, and hypoxia causes pulmonary vasoconstriction, Pulmonary capillary venous pressure increases; on the other hand, hypoxia stimulates a large release of catecholamines, causing systemic circulation vasoconstriction, increased peripheral total resistance, increased left ventricular afterload, altered left ventricular function, and decreased ejection fraction. At the same time, global myocardial hypoxia caused by high transmyocardial negative pressure and long-term hypoxia due to the increase in the absolute value of high intrapulmonary negative pressure will also lead to changes in left ventricular function. All these factors will promote the generation of pulmonary edema, and then a series of lung injuries will occur.

1.4 Bad gas exceeding the standard

The concentration of harmful gas ammonia in the chicken house is greater than 20 mg/m3, and the concentration of hydrogen sulfide is greater than 15 mg/m3. It will irritate the mucous membrane, and the shedding of cilia after the mucous membrane of the respiratory tract is damaged is conducive to the invasion of the lung by pathogens; when the carbon dioxide concentration is greater than 2500 mg/m3, it will affect the gas exchange, cause pulmonary hypertension and cause lung injury.

2. Pathogen infection

Common pathogens causing lung infection include: Escherichia coli, staphylococcus, mycoplasma, mold, H9, infectious bronchitis, etc.

2.1 Escherichia

coli pneumonia The basic feature of Escherichia coli pneumonia is the disturbance of pulmonary microcirculation. Due to the increased capillary permeability, a large amount of fibrinogen leaks out of the alveoli, resulting in extensive consolidation of the lung tissue. In the early stage of the disease, the lung lobes are congested and edematous, and there is a large amount of serous exudate in the alveolar cavity. Pulmonary succulent degeneration: When the exudate cannot be completely absorbed and cleared due to the low number of phagocytic cells or functional defects, it will be organized by granulation tissue, and the lung tissue at the lesion will become brown meat-like fibrous tissue.

2.2 Staphylococcus pneumonia

infection Staphylococcus disease Chicken lungs are black and purple, with light yellow and miliary large fibrous nodules on the surface and inside the substance.

2.3 Mycoplasma damage to the lung

Mycoplasma gallisepticum often causes complications than other microorganisms. Escherichia coli is one of the microorganisms that often coexist with mycoplasma. Newcastle disease, infectious bronchitis, etc. can all promote mycoplasma infection. When the three combine, they will produce a serious air sac infection and also cause lung infection.

2.4 Injury of

infectious bronchitis to the lungs Infected bronchitis virus-infected chickens for 18 hours can be seen with respiratory cilia defects, mucosal epithelial cells become round and fall off, and a small amount of heterophages and lymphocytes infiltrate, and the infected chickens have stuck trachea or bronchi Other exudates, in severe cases, can be seen with caseous emboli at the back end of the trachea or bronchi, and pneumonia areas of varying sizes can be seen around the large bronchi.

2.5 Injury to the lungs by chicken mold The

lungs and trachea turn black and purple, off-white, hardened, necrotic on the cut surface, cloudy in the air sacs, and mold nodules.

2.6 Lung damage caused by low-pathogenicity influenza (H9) The impact of

chicken low-pathogenicity avian influenza (such as H9N2) on the respiratory system is characterized by catarrhal, fibrinous, serous fibrinous, mucopurulent or fibrous Plain purulent inflammation. The tracheal mucosa is congested and edematous, and occasionally hemorrhages; at the same time, it also causes different degrees of inflammation to the lungs.

2. Preventive measures

1. Improve the environment

In the production process, the actual environment should be managed in strict accordance with the temperature, humidity, ventilation, and ventilation standards to provide a comfortable and healthy growth environment for the chickens. Chickens fed in an environment with an ammonia concentration of 10 mg/L or 20 mg/L had increased tracheal mucus secretion, rough cilia surface, and degraded mucociliary movement, and the elimination rate of E. coli in the air sacs, liver and lungs decreased. bacillary pneumonia, then flocks are more susceptible to infectious bronchitis and Newcastle disease. This shows the importance of the environment to the flock.

2. Formulate a reasonable immunization program. Formulate a reasonable immunization program

according to the actual situation in the breeding area, and try our best to make the antibody level of common diseases higher than the normal standard during the corresponding antibody trough period, so as to ensure that the chickens can safely pass through these corresponding antibody trough periods., so that the chickens grow healthily.

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