Prevention and treatment of porcine stress syndrome

Porcine stress syndrome is that pigs are stimulated by a variety of adverse factors, causing non-specific stress reactions, mostly in pigs to be slaughtered after closed feeding or transportation, manifested as pale, soft and water exudation of pork after death or slaughtering. thus affecting the quality of meat, the disease is more common at home and abroad, bringing huge economic losses to the pig industry, let's take a look at the prevention and treatment of porcine stress syndrome.

Etiology of porcine stress syndrome

1. Environmental factors: when stimulated by some adverse environmental factors in feeding and management, stress reactions are produced to improve the body's adaptation to the internal and external environment. Common stressors that can cause stress responses include infection, trauma, poisoning, high temperature, noise, transport, hunger, hypoxia, re-grouping, transport, mating, litter, etc. It leads to specific disorders and non-specific defense responses in the pituitary-adrenocortical system, resulting in stress syndrome.

2. Genetic factors: it is most common in pigs with lean meat type, plump muscle, short legs and strong body, such as Pittland pig, Bozhong pig, Landrace pig, and most of the pigs whose erythrocyte antigen is H system blood group are stress-sensitive pigs. Susceptible pigs are more easily frightened, difficult to control, and often show muscle and tail trembling.

Symptoms of porcine stress syndrome

1. Sudden death stress syndrome: sudden death occurs when transportation, preventive injection, mating and giving birth are stimulated by strong stressors, without any clinical symptoms and sudden death. The postmortem lesion was not obvious.

2. Malignant high fever syndrome: high body temperature, flushing skin, some showing purple spots, mucous membrane cyanosis, whole body trembling, muscle stiffness, dyspnea, tachycardia, tachycardia and even death. Postmortem rigor occurs, corpse decay is faster than normal, visceral congestion, pericardial effusion, pulmonary congestion, edema. This type of disease often occurs in crowded and hot seasons, when death is more serious.

3. Acute dorsal muscle necrosis: it mostly occurs in Landrace pigs. When acute syndrome lasts about 2 weeks after stress, the dorsal muscles of diseased pigs are swollen and painful, the spinous process arches or bends to the side, and is unwilling to move. When the swelling and pain subside, the diseased muscles atrophy, and the spinous process of the spine protrudes, and after a few months, there can be some degree of regeneration.

4. White pig meat type: the diseased pig initially showed rapid tail trembling, strong and stiff muscles, irregular pale area and erythema in the skin, and then turned to cyanosis. Dyspnea, even open mouth breathing, body temperature rise, collapse and die. Soon after death, the rigor, joints can not be flexion and extension, autopsy showed that some muscles pale, soft, water exudation characteristics. Postmortem 45min muscle temperature is still 40 ℃, pH is lower than 6, while normal pork pH should be higher than 6. This is related to the excessive decomposition of glycogen and the production of lactic acid after death, the rapid decrease of meat pH and the decrease of the binding capacity between depigmentation and water. This kind of meat is not easy to preserve and the cooking quality is poor. Some pork becomes darker red than normal, called "black hard dried pork" (DFD pork). This situation is common in pigs starving due to long-distance transportation.

5. Gastric ulcer type: stress causes exuberant secretion of gastrin in pigs, forming autologous digestion, resulting in erosion and ulcer of gastric mucosa. Acute cases, the appearance of good development, easy to vomit, stomach contents with blood, feces in the form of coal tar. In some cases, there is massive bleeding in the stomach, a drop in body temperature, pale skin on the mucous membrane and body surface, and sudden death. Chronic cases, loss of appetite, weak, slow movement, sometimes abdominal pain, bow to the ground, discharge dark brown stool. If the gastric wall is perforated, the secondary peritonitis dies. Some pigs only find stomach ulcers during slaughter.

6. Acute enteritis edema type: the common piglet dysentery and swine edema disease in clinical treatment are mostly caused by Escherichia coli and are related to stress reaction. Because in the process of stress, the defense function of the body decreases, Escherichia coli becomes a conditional pathogenic factor, leading to non-specific inflammatory pathological process.

7. Chronic stress syndrome: due to the low intensity of stressor, the reaction caused by continuous or intermittent repetition is mild and easy to be ignored. In fact, they have formed adverse cumulative effects in pigs, resulting in reduced production performance, weakened defense function, and easy to cause a variety of diseases caused by secondary infection. The blood biochemical changes before death were the increase of serum lactic acid, the decrease of pH and the increase of creatine phosphokinase activity.

Prevention and treatment of porcine stress syndrome

1, treatment: the principle is to sedate and supplement corticosteroids, first transfer to the non-stress ring, spray the skin with cold water. Pigs with mild symptoms can recover on their own, but pigs with purple skin and stiff muscles must use sedatives, corticosteroids and anti-stress drugs. If chlorpromazine hydrochloride is selected as a sedative, the dose is 1mg / kg body weight. One intramuscular injection, or diazepam 1mg / kg body weight, an intramuscular injection. Can also choose vitamin C, sodium selenite vitamin E mixture, diphenhydramine hydrochloride, sodium salicylate and so on. Use antibiotics to prevent secondary infection. 5% sodium bicarbonate solution can be injected intravenously to prevent acidosis.

2. Prevention: ① should strengthen genetic breeding and breeding, and gradually eliminate stress-susceptible pigs through halothane test or creatine phosphokinase activity detection and blood group identification. ② minimizes the stress factors such as feeding and management to cause disease in pigs. Such as improve feeding management, reduce all kinds of noise, avoid overcooling or overheating, dampness, crowding, reduce driving, capture, anesthesia and other stimuli. Avoid congestion and overheating during transportation, and avoid driving and stimulating pigs with electric rods before slaughtering. Before possible stress, the use of sedatives such as chlorpromazine, diazepam and supplementation of selenium and vitamin E can reduce the death rate caused by stress.