Causes and symptoms of new layer disease?

New layers disease, also known as pre-laying stress syndrome, refers to a disease that occurs 119 days after the chicken has just started to lay, and because its onset and death are relatively sudden, some people call it sudden death of laying hens. This disease is a conditional disease, which occurs when the conditions are met. With the development of the breeding industry, new hen disease has become a prominent conditional disease in the production of laying hens in my country. The disease can occur all year round, especially in winter and summer. This article elaborates on the causes of disease, epidemic characteristics, clinical symptoms, and changes in necropsy, and proposes reasonable diagnosis methods and preventive measures in order to provide a reference for the treatment of the disease.
　　1 Cause of disease
　　1.1 Effects of Clostridium botulinum toxin
　　 Clostridium botulinum is widely found in nature such as water, soil, livestock and poultry manure and moldy feed. The toxin toxicity of the bacteria can be activated and enhanced by trypsin in an alkaline environment. These toxins are absorbed by the gastrointestinal tract and act on the cranial nerve nucleus, autonomic nerve endings and peripheral nerve muscle junctions to prevent the release of acetylcholine and cause muscle paralysis.
　　1.2 Unreasonable feed formula
　　 Due to changes in the physiological and reproductive performance of the hens after birth, some endocrine functions are changed, resulting in increased consumption of nutrients such as protein, vitamins, calcium, phosphorus, and energy. At this time, if the feed formula is unreasonable and the feed intake is reduced, it is very easy to cause the disease.
　　1.3 Respiratory alkalosis
　　 Chicken flocks mainly rely on breathing to remove heat, but it will cause a large amount of carbon dioxide to be lost, and the body's pH will rise, leading to high alkalinity and inducing the disease.
　　1.4 Increased blood viscosity
　　After the lights are turned off at night, the chickens still have to urinate to dissipate heat. Urination will cause the water in the blood to decrease rapidly and become thicker, reduce the oxygen carrying capacity, reduce blood volume, and die from heart failure.
　　1.5 Other reasons
　　 Due to the rich feathers of new hens, the amount of activity in the evening is reduced, and the heat is not easily released. Heat stress causes the increase in body temperature to induce the disease. Generally, the peak of death is 1 to 2 in the morning. In addition, in summer, when the temperature difference between indoor and outdoor is too small or the ventilation is poor, the blood oxygen content in the chicken body is too low, which leads to the disease.
　　2 Popular features
　　Laying hens are more prone to outbreaks of the disease, especially in peak-laying chickens and primiparous chickens. Generally speaking, the higher the mortality of chickens, the higher the laying rate. The disease often occurs when normal chickens suddenly become paralyzed. At this time, if it can be detected in time, the paralyzed chickens can be slowly recovered by quarantining them outside. Although this disease can occur throughout the year, it often occurs when the weather suddenly becomes hot. The death of new hens usually occurs at night, and the dead chickens are only found when the chickens are fed in the morning. Most of the chickens infected with this disease are obese chickens, and the dead chickens often have prominent cloacas.
　　3 Clinical symptoms
　　 The disease can generally be divided into two types, acute and chronic.
　　3.1 Acute symptoms
　　 Chickens suffering from this type of chickens often die suddenly. They were normal before the onset, and usually occurred in the second half of the night. After the start of production, the chickens died when the egg production rate reached 20 to 80%. During the day, dead chickens could not be picked out from flocks with better egg laying and healthy appearance, but dead chickens were seen in the cage the next morning. The higher the flock, the higher the incidence. Dead chickens generally show purple crown tips, good body weight, anal ectropion, necropsy reveals pulmonary congestion, liver fragile congestion, black intestine, and hyperemia of the vitelline membrane. Because chickens suffering from the disease have gastrointestinal symptoms, it is easy to be misdiagnosed as coliform disease, Newcastle disease and influenza disease.
　　3.2 Chronic symptoms
　　 Chronic symptoms of chickens are often paralyzed or hemiplegic due to muscular nerve paralysis. Isolate the sick chicken outside the cage, showing dry skin, sunken eyes, yellow-green loose stools, and soft-shelled eggs or sand-shelled eggs. However, after administering antibiotics, vitamins and other drugs to the sick chickens, 80% of the sick chickens raised for 1 to 3 days alleviated symptoms and slowly recovered.
　　4 Necropsy changes
The phenomenon of holding eggs is often seen in anatomical chickens, followed by thinning or perforation of the glandular stomach wall, ulcer or erosion of the glandular stomach, the papilla of the glandular stomach flowing out of liquid, which is yellowish brown; the intestinal mucosa falls off, the intestinal bleeding can be seen, and the contents are dark brown or Off-white. Follicular congestion and bleeding can be seen in some sick chickens after anatomy; fallopian tube congestion and edema, and undischarged hard-shelled eggs can be seen in front of the fallopian tube cloaca; liver yellowing, swelling, congestion, lung congestion, heart dilation, sometimes in the lungs, There are bleeding spots on belly fat and liver.
　　5 Disease diagnosis
　　 The disease can be diagnosed by anatomy. Anatomical diseased chickens can show follicular congestion, pulmonary congestion, liver enlargement accompanied by bleeding spots and blood stasis, heart dilation, hard eggshells in the fallopian tubes, and fallopian tube congestion and edema. The intestinal mucosa can be seen falling off, there is bleeding in the intestine, the contents are gray-white or dark-brown, accompanied by glandular gastric ulcer. In addition, this disease is similar to the symptoms of chicken fatty liver syndrome, so pay attention to distinguish it.
　　6 Prevention measures
　　6.1 Disease prevention
Since this disease is a conditional disease, the following measures should be taken to prevent the occurrence of this disease: (1) Change the light and feed in a gradual manner, especially when growing chickens are overwhelmed by laying hens, in addition to reducing light stress and feeding stress The intensity of the chicken flock smoothly transition to the laying stage. (2) Drinking water is sufficient. Be careful to control the water temperature, especially in summer, use a thermometer to measure the water temperature and control the temperature at 18-21 ℃. (3) With the development of the chicken industry, the increase in the intensity and frequency of vaccine immunity is likely to trigger a stress response, leading to an increase in the demand for various nutrients. To ensure that the nutrient concentration in the diet is high enough, in order to produce specific immune protection, that is, antibody-immunoglobulin, it is necessary to increase the protein concentration in the diet. (4) Strengthen ventilation, reduce stocking density, and prevent high temperature and hypoxia. (5) Appropriately add VC and multivitamins to the diet to enhance the resistance of the chickens to stress. Particular attention should be paid to supplementing calcium, phosphorus, VA and VD, which can maintain the integrity of the intestinal mucosa and fallopian tube mucosa, and promote nerve conduction.
　　6.2 Disease treatment
　　 For chickens suffering from this disease, in order to reduce the burden on the heart and reduce blood viscosity, the lights can be turned on once at night, and fresh cold water can be given to the sick chickens. For paralyzed chickens, they should be fed separately. In order to avoid a more serious situation. Research reports have shown that before and after the hen sees eggs, using Chinese medicine for 7 days of warming the palace and promoting blood circulation, invigorating the kidney and spleen, and regulating the reproductive system can dredge the fallopian tube, thereby enhancing the function of the fallopian tube; when the laying rate of the hen reaches 60%, continue to use traditional Chinese medicine A week of conditioning can promote the neatness of laying eggs. In addition, in order to prevent hen enteritis and salpingitis, increase its contraction ability, and protect its normal function, drugs such as probiotics can be used.