Factors causing stress in Pigs and Preventive measures

Stress in pigs is an inevitable problem in the production process. The harm caused by stress is both single and comprehensive, and its effects are multifaceted. If we can properly take various preventive measures according to different specific conditions, the losses caused by stress will be greatly reduced.

Stress is the sum of non-specific responses of organisms to various very stimuli, and general stimuli cause specific responses of organisms. Some stimuli not only cause specific responses, but also cause non-specific responses, which are as follows:

The adrenal cortex of ① became thicker and its secretory activity increased.

② thymus, spleen and other lymphoid tissues atrophy, blood eosinophils and lymphocytes decreased, neutrophils increased.

③ gastric and duodenal ulcer bleeding. These symptoms are called systemic adaptation syndrome (GAS). So stress is not environmental stimulation, but the response of the body.

First, the emergence and development of stress can be divided into three stages under typical circumstances.

1. Panic reaction and mobilization stage: GAS reaction appeared, alienation was dominant, pigs were emaciated, negative balance of nitrogen and carbon appeared, and body resistance was lower than normal level. This stage is generally 6-48 hours, if the stress factors are very strong, pigs may die within 1 hour or Id; if the body overcomes the influence of stress factors and survive, then enter the adaptation stage.

2. adaptation or resistance stage: the body acquires adaptation, the metabolism returns to normal, the assimilation is dominant, the physical condition is restored, the body resistance is raised above the normal level, and the resistance to other stimuli is also improved. This stage is usually a few hours, days or weeks. If the stressor stops acting or weakens, and the body overcomes the adverse effects of stimulation, stress ends at this stage, and in most cases stress only goes through the above two stages, but if the stressor continues to act or the body cannot overcome this effect, then enter the failure stage.

3. Failure stage: this stage is very similar to the panic stage, but the degree of reaction increases sharply. Although the adrenal cortex is hypertrophic, it can not produce the necessary hormones; the body storage, such as tissue protein and fat, is decomposed, and the body weight drops sharply; the acquired resistance is lost again, the adaptive function is destroyed, the system is dysfunctional, and finally the failure leads to death.

2. Stressors and their effects

1. Stressor

Stress can cause non-specific response in pigs, that is, systemic adaptation syndrome (GAS). All stimuli that can cause GAS in the body are called stressors or stressors. Habits can be divided into:

① feeding and management factors: including imprisonment, secret feeding, capture, group conversion and transportation, fighting, malnutrition, immunization, castration, ear labeling, tail amputation, etc.

② environmental factors: including extreme heat, severe cold, strong radiation, low pressure, toxic and harmful gases, dust, moisture, strong wind and thief wind, noise, etc.

③ microbial infection factors: bacteria, viruses, parasites, mycoplasma and chlamydia

④ other human factors, such as strength utilization of production performance, discomfort to machinery and equipment, etc.

⑤ genetic factor: recessive halothane gene homozygous pig, prone to stress syndrome.

2. The harm of stress

(1) the quality of pork is decreased.

① gray color, soft meat, moisture exudation of PSE meat, mainly due to congestion in transportation, bundling, cold, heat stimulation; pig muscle dry, rough texture, dark color of DFD meat, mainly due to long-term stimulation by low-intensity stressors.

② parenchyma myocarditis (acute heart failure) often occurs in 4-6-month-old pigs and is characterized by sudden death without warning.

③ showed that the myocardium was pale, gray or yellow-white, striped or spotted degeneration.

④ adult pig dorsal muscle necrosis, postmortem dorsal muscle necrosis can be seen.

Acute leg muscle necrosis in ⑤ pigs showed acute serous necrotic inflammation, which was mainly caused by binding and extrusion during long-distance transportation.

(2) low immunity.

Under stress, it causes the atrophy of thymus, spleen and lymphoid tissue, hinders the production, differentiation and activity of eosinophils, T lymphocytes and B lymphocytes, weakens the phagocytic activity of blood and the level of antibody in vivo, thus suppresses the cellular and humoral immunity of the body, resulting in the decrease of immunity and disease resistance. Escherichia coli, Pasteurella multocida and other bacteria propagate rapidly, enhance their virulence, invade the blood, and cause pig gastric ulcer, bacteremia, death syndrome and so on.

(3) production performance is reduced.

During stress, the body must mobilize a large amount of energy to deal with the stimulation of stressors, so as to enhance the catabolism of protein, carbohydrate and fat, decrease the anabolism and increase the secretion of glucocorticoid. It leads to growth stagnation, weight loss and feed conversion rate, which is characterized by serious fattening of livestock during transportation and during slaughter.

(4) decrease of fecundity.

Stress can reduce the secretion of follicular hormone (FSH) and prolactin (LTH), gonadal hypoplasia in young pigs, gonadal atrophy, decreased libido, sperm and egg dysplasia in adult pigs, and affect the implantation of fertilized eggs and fetal development, resulting in early absorption, abortion, fetal malformation or stillbirth.

(5) the cannibalism of the same kind will be caused in the case of high density feeding.

(6) in the process of long-distance transportation, it is easy to cause acute mycoplasma pneumonia, solar radiation disease, heat radiation disease and so on, which is characterized by mental depression, elevated body temperature, accelerated breathing, mucosal cyanosis, muscle tremor, mouth foam or vomiting.

Measures to reduce the effect of stress

The main results are as follows: 1. Different anti-stress pig breeds have different sensitivity to stress. When purchasing and introducing pig seedlings, attention should be paid to selecting varieties with strong anti-stress performance.

2. The building structure of the pig house should be scientific and reasonable, and the small environmental conditions should be improved.

3. According to the different growth periods of pigs, the nutrition level of dietary feed should be rationed scientifically to meet the needs of animals, and fed regularly and quantitatively. Do not feed moldy and deteriorated feed, clean and disinfect drinking water, adequate feeding trough and sink facilities, pay attention to hygiene, avoid food fighting and uneven intake. At the same time, we can do a good job in the following areas:

(1) the right amount of carbohydrates and fats

2% vegetable oil is added to the diet of growing pigs, and the content of carbohydrates is reduced accordingly, which can reduce the heat increase of pigs, reduce the heat dissipation burden of pigs, and alleviate high temperature stress.

(2) reasonable proteins and amino acids

It has been reported that balancing amino acids and reducing crude protein intake are important measures to alleviate heat stress in pigs. Feeding lysine instead of natural protein is beneficial to pigs because lysine reduces the heat consumption of diets. In the hot climate, if the lysine content in the diet was increased on the basis of ideal protein, the feed conversion rate could be improved, and there was no significant difference in performance and carcass quality between pigs and conventional diets.

(3) adding vitamins

In hot weather, adding 100g stress hormone per 150kg feed can help to reduce the effect of heat stress on sperm quality and fertilization rate; regulate material metabolism in pigs, enhance immune function, improve anti-stress ability, reduce body temperature and breathing times of meat pigs under heat stress, and effectively improve the production performance of fattening pigs; it can also effectively prevent diarrhea due to lack of vitamin E.

(4) use of trace elements

① chromium supplementation plays a certain role in resisting stress, improving production performance, regulating endocrine function, affecting immune response and improving carcass quality.

② copper has antimicrobial properties, and copper combined with antimicrobial agents can play a synergistic effect.

Adding arsenic preparation to the diet of ③ piglets can effectively control diarrhea and increase weight gain.

④ selenium is a component of glutathione peroxidase (GSH-PX) in livestock and poultry. Through this enzyme, peroxides are turned into harmless alcohols to prevent unsaturated fatty acids in cell lipid membrane from being damaged by peroxides. The addition of organic selenium has a positive effect.

(5) Drug prevention and treatment of stress.

In order to improve the anti-stress ability of the body and prevent stress, anti-stress drugs can be given through feed, drinking water or other ways. At present, anti-stress drugs are the most active field in anti-stress research, and have made great progress.

(6) to prevent stress during transportation and slaughtering.

It is best to fast before transportation, and 100 grams of hormone can be added to 300 kg of drinking water. It can prevent the influence of adverse factors such as congestion, sunlight, wind and rain in transportation. The waiting time should be appropriate.