What should we do if the pig population is weak? How to improve the nonspecific immunity of pigs?

The breeding and improvement of modern pigs is carried out according to human needs. The goal is to make pigs eat less, grow faster, produce more and have a high lean meat rate. It is difficult for the natural environment to meet these requirements, so it is necessary to perform well in the artificial environment!

The cooling and heat preservation, dry humidity control, sewage system, air quality in the livestock house, logistics system, feeding system, equipment quality, production management, feed and nutrition, breeding technology and so on all affect the production performance and health status of pigs.

The current situation we are facing is that there are more and more pig epidemics, more and more vaccines and veterinary drugs, and it is more and more difficult to raise pigs. Many pig farms still have no profits or even losses when the pig market has reached a record high and lasted the longest.

Then we can’t help but reflect on whether the current method to deal with pig epidemic disease is correct or whether the direction is wrong. We need to reflect on the root causes of the disease in the pig industry. Is it because the virus and bacteria are too strong or the constitution of pigs is too weak?

So now the industry is paying more and more attention to the non-specific immune function of pigs!

Factors affecting nonspecific immune function of pigs:

1.    Nutrition

In the process of pathogenic infection, the immune system of animals is activated, the body synthesizes a large number of cytokines, chemical factors, acute phase proteins, immune antibodies, etc., the metabolic rate is significantly enhanced, the heat production is increased and the body temperature is increased, which requires a lot of nutrients.

First, a large number of amino acids are needed to synthesize proteins, antibodies and other active substances in the acute phase, resulting in increased body protein loss and nitrogen excretion. In the process of pathogenic infection, the supply of amino acids mainly comes from the degradation of body protein because the appetite and food intake of animals are greatly reduced or even fasted. Enhanced metabolism will inevitably increase the demand for vitamins and trace elements.

On the other hand, the challenge of epidemic diseases leads to oxidative stress in animals, producing a large number of free radicals and increasing the consumption of antioxidants (VE, VC, Se, etc.).

In the challenge of epidemic disease, animal metabolism is enhanced, the need for nutrients is increased, and the nutrient distribution of animals is changed from growth to immunity. These metabolic reactions of animals are to resist epidemic diseases and survive as much as possible, which is the result of long-term evolution or natural selection. However, under artificial selection, the metabolic pattern of pigs in the challenge of epidemic disease deviates from the track of natural selection.

In recent years, the progress of pig breeding has greatly improved the growth potential of pigs and the growth rate of lean meat. Once such pigs are infected, the distribution mode of available nutrients changes to a certain extent: the nutrients allocated to the immune system decrease and the nutrients allocated to growth increase.

Under healthy conditions, this is naturally beneficial to improve production performance (pig breeding is carried out under very healthy conditions), but when challenged by epidemic diseases, such pigs have low immunity and higher mortality than old varieties (local pigs in China grow slowly, but their disease resistance is much higher than modern foreign pigs).

Continuous focus on the choice of improving growth performance has genetically changed the distribution of nutrients, which must sacrifice functions other than growth. Therefore, raising lean pigs with high production potential must provide a high nutritional level, especially in the challenge of epidemic diseases, so as to ensure the supply of nutrition, so as to have enough nutrients for immunization, and pigs can overcome epidemic diseases.

In case of low tide of pig raising or economic difficulties in pig farms, reduce the feed supply of pigs. Once the epidemic strikes, the consequences are likely to be disastrous.

2.  Stress

Stress destroys the mucosal structure of pigs and increases the risk of infection in pigs.

Stress leads to the increase of oxygen free radicals and destroys the permeability of cell membrane. The permeability of cell membrane increased, which was more conducive to the entry of bacteria into cells; Stress leads to excitation of sympathetic adrenal medullary system, continuous contraction of visceral vessels, mucosal ischemia, hypoxic injury, ulcer erosion; Stress leads to metabolic disorder, increase of intracellular acidic substances and mucosal damage caused by cellular acidosis; Stress leads to increased glucocorticoid secretion and glucocorticoid inhibits mucosal cell regeneration.

Stress increases the risk of detoxification in pigs.

Various stress factors cause the body to produce a large number of oxygen free radicals, which damage vascular endothelial cells, induce intravascular granulocyte aggregation, accelerate the formation of microthrombosis and endothelial cell damage, facilitate the spread of virus, and increase the risk of detoxification.

Stress reduces body resistance and increases the risk of instability in pigs.

On the one hand, endocrine regulation during stress will inhibit the immune system, such as glucocorticoid has an inhibitory effect on immune function; On the other hand, the increase of oxygen free radicals and pro-inflammatory factors caused by stress will directly damage immune cells, resulting in the decrease of the number of immune cells and the insufficient secretion of interferon, resulting in immunosuppression.

Specific manifestations of nonspecific immune decline:

● eye excrement, tear spots, back bleeding and other three dirty problems

Back bleeding, old skin and other problems indicate that the body’s first immune system, body surface and mucosal barrier are damaged, resulting in easier entry of pathogens into the body.

The essence of lacrimal plaque is that the lacrimal gland continuously secretes tears to prevent further infection of pathogens through lysozyme. Lacrimal plaque indicates that the function of local mucosal immune barrier on the ocular surface is reduced, and the pathogen has not been completely removed. It also showed that one or two of SIgA and complement proteins in ocular mucosa were insufficient.

● sow performance degradation

The elimination rate of reserve sows is too high, pregnant sows abort, give birth to stillbirths, mummies, weak piglets, etc;

Prolonged estrous interval and return to estrus after weaning; The milk quality of lactating sows decreased, the immunity of newborn piglets was poor, the production was slow, and the diarrhea rate was high.

There is a mucosal system in all mucosal parts of sows, including breast, digestive tract, uterus, reproductive tract, renal tubules, skin glands and other submucosa, which has a multi-level immune barrier function to prevent pathogen infection.

Take the eye as an example:

① Ocular epithelial cell membrane and its secreted lipid and water components form a physical barrier to pathogens.

② Antibacterial components secreted by glands in ocular mucosal epithelium, such as tears secreted by lacrimal glands, contain a large amount of lysozyme, which can kill bacteria and inhibit bacterial reproduction, and form a chemical barrier to pathogens.

③ Macrophages and NK natural killer cells distributed in the tissue fluid of mucosal epithelial cells can phagocytize pathogens and remove cells infected by pathogens, forming an immune cell barrier.

④ The local mucosal immunity is composed of immunoglobulin SIgA secreted by plasma cells distributed in the connective tissue of subepithelial layer of ocular mucosa and complement protein corresponding to its quantity.

Local mucosal immunity plays an important role in immune defense, which can finally eliminate pathogens, promote health recovery and prevent repeated infection.

The old skin and tear spots of sows indicate the damage of overall mucosal immunity!

Principle: balanced nutrition and solid foundation; Liver protection and detoxification to improve health; Reduce stress and stabilize internal environment; Reasonable vaccination to prevent viral diseases.

Why do we attach importance to liver protection and detoxification in improving non-specific immunity?

The liver is one of the members of the immune barrier system. Innate immune cells such as macrophages, NK and NKT cells are the most abundant in the liver. Macrophages and lymphocytes in the liver are the key to cellular immunity and humoral immunity respectively! It is also the basic cell of nonspecific immunity! Sixty percent of macrophages in the whole body gather in the liver. After entering the liver, most of the antigens from the intestine will be swallowed and cleared by macrophages (Kupffer cells) in the liver, and a small part will be purified by the kidney; In addition, most of the viruses, bacterial antigen antibody complexes and other harmful substances from the blood circulation will be swallowed and cleared by Kupffer cells to prevent these harmful substances from damaging the body. The toxin waste purified by the liver needs to be discharged from bile to the intestine, and then discharged from the body by feces.

As the metabolic transformation center of nutrients, liver plays an irreplaceable role in the smooth transformation of nutrients!

Under stress, pigs will increase metabolism and improve the anti stress ability of pigs. In this process, free radicals in pigs will increase greatly, which will increase the burden of pigs and lead to the decline of immunity. The production of free radicals is positively correlated with the intensity of energy metabolism, that is, the more vigorous the metabolism of the body, the more free radicals will be produced. The more vigorous the metabolism of organs, the easier and stronger they will be attacked by free radicals. For example, the liver contains a variety of enzymes, which not only participate in the metabolism of carbohydrates, proteins, fats, vitamins and hormones, but also have the functions of detoxification, secretion, excretion, coagulation and immunity. It produces more free radicals and is more harmful by free radicals.

Therefore, to improve non-specific immunity, we must pay attention to liver protection and detoxification of pigs!