The immune response is a biological process that is affected by many factors. In the vaccinated pigs, different individuals have different levels of immune response, some are stronger, some are weaker, and most of them have strong immunity after vaccination. However, vaccination does not mean that they have obtained There are many factors that cause immunity failure:

1, environmental factors

The environment includes the body's internal and external environment. The in vivo environment refers to the physiological environment in the body. The in vitro environment includes nutrition and the living environment of the pig. Maintaining a good in vivo and in vitro environment is a necessary condition for the body to have normal immunity; improving the in vivo and in vitro environment is an important measure to improve the body's overall immunity. A good in vivo environment must be achieved by providing a good in vitro environment; at the same time, the in vitro environment also directly affects the body's immune function.

Nutrition is the first factor in the external environment that affects the body's immunity. Nutrition is the material basis for the body's metabolism and production performance as well as the development and function of the immune system. Lack or excess of nutrients can lead to a decline in immunity. The effects of various nutrients on immunity are mainly:

Proteins and Amino Acids: Deficiency of proteins can cause atrophy of the thymus of immune organs, a decrease in the number of lymphocytes in the blood, and a decrease in complement titer. Lack of methionine can cause atrophy of the thymus and spleen; threonine deficiency inhibits Ig formation, and the production of T cells, B cells, and antibodies; cysteine ​​has extreme protection in protecting cells from the harmful effects of reactive oxygen species and scavenging free radicals. The important role.

Fat: High-fat diets inhibit lymphocyte transformation. Excess saturated fatty acids inhibit the phagocytosis of immune cells. Corn oil, linseed oil, and cocoa butter, which are rich in unsaturated fatty acids, increase antibody production.

Vitamins: Vitamins are important nutrients for maintaining immune function. VA is a factor involved in the activation of T cells. VA deficiency can block the activation of T cells and lead to a decrease in Ig levels. At the same time, VA also regulates the number of T cell differentiation subpopulations in lymphocytes and peripheral blood. VE can enhance the body's immune system, it can enhance the phagocytosis of immune cells, reduce stress response, protect the lymphocyte membrane, and maintain the integrity of the immune system. Other vitamins, such as folic acid, pantothenic acid, riboflavin and choline, also have important effects on immunity.

Minerals: Iron deficiency leads to anemia and serum complement activity decreases, affecting DNA and protein synthesis; however, high copper can increase the body's sensitivity to bacterial and parasitic infections. The lack of zinc can cause atrophy of the thymus, increased adrenal corticosterone, and leukopenia. And its phagocytic activity is inhibited or even completely lost; but excessive zinc can also make the immune suppression. Selenium is an immune promoter, and selenium deficiency can cause lymphoid tissue necrosis. Chromium is a component of the glucose tolerance factor, and increasing chromium promotes the production of T cells and B cells.

The immune response of pigs to vaccination is genetically controlled to a certain extent. Pigs of different breeds and even individuals of the same breed have different responses to the same vaccine. Some pigs are born with innate immunity. defect.

The pathogens of some pig diseases (such as porcine reproductive and respiratory syndrome, circovirus, eperythrozoonosis, etc.) can damage some of the immune organs of the pig, thus reducing the body's immune response capability. When the herd is onset, more or less stress is exerted on the herd, leading to a decrease in its immune response capacity.

The immune function in pigs is regulated by nerves, body fluids and endocrine to some extent. When the environment is too cold, overheated, over-humid, and poorly ventilated, it will lead to different degrees of stress response of pigs, leading to a decrease in the immune response ability of pigs to antigens. After immunization, no corresponding immune effects can be obtained, which is manifested as antibody levels. Low, the cellular immune response is weakened. Although multiple immunizations can make the antibody level high, it is not a goal to be achieved in disease prevention. It has been shown that after multiple immunizations of animals, high levels of antibodies will reduce the productivity of animals.

2, the quality of the vaccine

Vaccine refers to biological products made by breeding and processing of pathogenic microorganisms with good immunogenicity. Vaccinating animals can produce corresponding immune effects. Vaccine quality is a key factor in the success of immunization. Vaccine quality must be safe and Effectively, the Ministry of Agriculture requires that manufacturers of biological products must meet GMP standards. Generally, attenuated virus seedlings and wet seedlings should be kept below -15°C. Inactivated seedlings and heat-resistant lyophilized attenuated vaccines should be stored at 2°C~8°C. During transportation and preservation, the "cold chain" system must be used to avoid temperature. Fluctuations, avoid repeated freezing and thawing, otherwise cause inactivation or reduced potency. Inactivated seedlings must be prevented from freezing, otherwise they will break or show agglomeration and affect the immune effect.

3, the dose of immunity

There is a breeding process in the body after inoculation of the virus seedlings. The vaccine that is inoculated into pigs must contain a sufficient amount of viable antigens to stimulate the body to produce the corresponding antibodies and gain immunity. If the dose of immunity is insufficient, it will lead to low immunity or induce immune tolerance; and if the dose of immunity is too large, it will also produce strong stress, weakening the immune response and even causing immune paralysis.

4, stress factors

Temperatures that are too high or too low, crowded, mixed with the bar, restocking, weaning, cutting, tailing, deworming, food restrictions, transportation, noise, and restraints are common stress factors. Among the above factors, extreme temperature should have the highest impact on immunity, especially the high temperature is even more harmful to immunity. Stress is mainly through the hypothalamus-pituitary-adrenal axis acting on the immune system, causing the adrenal gland to produce large amounts of cortisol and corticosterone. Corticosterone suppresses protein synthesis in immune organs and lymphoid tissues: Excessive secretion of cortisol over a long period of time can lead to atrophy of the thymus and lymphoid tissues. It also suppresses the activity of natural killer cells and inhibits the production of antibodies and lymphocyte activating factors. In addition, stress can increase the content of cyclic adenosine in lymphoid tissues. Studies have shown that cyclic adenosine has immunosuppressive effects. Stress also increases the secretion of thyroid hormones and suppresses the immune response. At this stage, it is best to add more electrolytes and vitamins, especially vitamins A, E, C and compound B are more important.

5, harmful gases (such as ammonia and hydrogen sulfide) and dust particles

Poor ventilation and poor management in the pig house. When the concentration of these harmful components in the air is too high and the action time is too long, the function of the cilia-mucosal structure will be destroyed, leading to respiratory infection and related inflammation. More seriously, it will lead to the response of airway-associated lymphoid tissues to antigens.

6, other immune poisons

Including mycotoxins, pesticides, veterinary drug residues and heavy metals, harm the animal's body through feed and drinking water. When pigs come into contact with these poisons, even at lower doses, they can damage immune organs, cause immunosuppression, and make pigs susceptible to infectious diseases. Sex hormones have an inhibitory effect on the immune response, such as testosterone, androgen have a certain impact on the immune response of pigs. In the use of sex hormone drugs should pay attention to the changes in the immune level of the herd. Antimicrobial drugs florfenicol, gentamicin, ceftiofur, enemy bacteria net, olaquindox, etc., anti-parasitic drugs monensin, salinomycin, grams of ball powder, corticosteroids Misosone, hydrocortisone, prednisone, etc. have a certain inhibitory effect on the proliferation of B lymphocytes, affecting the immune response of pigs. In general, it is best not to use antibiotics and other antibacterial drugs at the same time as vaccination with live bacterins; immunization of pig houses within two days before and after immunization.

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