Ministry of Agriculture and Rural Affairs of the People's Republic of China Proclamation No .194: Since July 1,2020, feed production enterprises must stop producing commercial feed containing AGP.
The policy has put a strain on enterprises using antibiotics in feed of animals, especially suckling piglets. In face of this policy, we do understand that it is not to seek alternatives to antibiotics, but to design an antibiotic-free feed to meet the production needs of piglets or even have a better production performance.
What are the basic requirements for better production performance of suckling piglets? To make it simple: more feed intake, less diarrhea; faster growth, low FCR; high disease resistance, high survival rate.
The following figures analyzes in detail the main factors affecting these requirements and it can be found that all items are related to "intestine". By solving the problem of intestinal health can not only maximize the production performance of suckling piglets, but also set up the foundation for the design of antibiotics-free feeds.
It looks simple, but hard to do! To solve the intestinal health problems of suckling piglets, we must know what is wrong with the intestine. In the research article of Moeser et,. al (2017) , it is explained clearly. We study and share the main contents as below:
After the piglets were born, within 36 h, a passive immunity from maternal antibodies will be acquired. At this time, both active immunity and intestinal permeability were inhibited. However, with the increase of age, the passive immunity of piglets is gradually decreasing while the active immune system increasing. Furthermore, if the piglets keep suckling by sow until the age of 12 to 14 weeks, a more perfect active immune system as well as the intestinal epithelial barrier function, transport function, nervous system can be well established, and abnormal conditions, like diarrhea, low feed intake, slow growth, etc.) will almost not happen. However, the forced weaning (25/28 day-old) in production practices will result in an "critical window of postnatal" (25/28 day-old to 84/98 day-old) in the intestine.
During this period, the inability of piglets to obtain bioactive components from milk, combined with stress, especially weaning stress (changes in psychology, environment, diet, etc.), lead to the following major changes in the intestine:
Increased intestinal permeability (reach maximum within 24 h after weaning, decreasing gradually after 2 weeks)
Increased number and activity of mast cells (increased inflammatory response)
Weakened the function of immune system
Nervous system hyperexcitability
Abnormal symptom usually occur in production (e.g. diarrhea, decreased feed intake, slow growth, high FCR), some pigs can be recovered within 2 to 3 weeks, and some pigs may be recovered for a long time or even may not be recovered, become susceptible pigs or ill pigs, various stresses (especially weaning stress) encountered by piglets during the critical window of postnatal, lead to damage the intestinal physical barrier and immune barrier function, which is the core to intestinal health.
As we can see this figure: In face of forced weaning in production of suckling piglets, the construction of good intestinal physical barrier and immune barrier function are the main means.
Normally, in intestine, there're four major barriers: microbial, chemical, physical, and immune, is it enough to only concern on these two barriers?
Based on the research studies of Duerkop et al .(2009) clarify and here we share the main points.
- Microbial barrier: It is composed of pathogenic bacteria, conditional pathogenic bacteria, and symbiotic bacteria. Under normal circumstances, the types and numbers of bacteria are in a balanced status. When indigestion of nutrients, especially inadequate digestion protein fermented by microorganisms, it will change the intestinal environment, which is beneficial to the growth of pathogenic bacteria or conditional pathogens. It multiplies in large numbers and breaks the balance. At this time, pathogenic bacteria and conditional pathogens will attack the physical barrier of the intestine and activate the intestinal immune system. It can be seen that adequate digestion and absorption of nutrients (especially proteins) are the key measures to regulate the microbial barrier, and the digestibility of nutrients and physical barrier of the intestine directly affect the digestion and absorption of nutrients.
- Chemical barrier is consist of mucus, digestive juice and anti-bacteria substances secreted by the intestinal epithelium. It plays an important role in digestion of nutrients and resisting invasion of pathogenic bacteria. Since these substances are derived from intestinal microorganisms, physical barriers, and immune barriers, ensure the normal function of intestinal microorganisms, physical and immune barriers is a key measure for regulating chemical barriers.
- Physical barrier is composed of tight junction between intestinal mucosa epithelial cells, which can effectively prevent harmful endotoxins derived from antigens, toxins, oxidative products of the diet, from entering the body. The rapid proliferation and differentiation of intestinal epithelial cells (usually they’re updated once in 3-5 days), integrity of epithelial cells, and low epithelial permeability are the key measures for regulating physical barrier of intestine.
- Immune barrier is consist of gut-associated lymphoid tissue, including lymph nodes, Kupper cells, can clear or reduce the damage to the body caused by toxic and harmful substances that have passed through the physical barrier of the intestinal tract. The first reaction after activation of immune system is acute inflammation, which is accompanied by a large number of free radicals. If the inflammation cannot be controlled, it will evolve into chronic inflammation, resulting in intestinal tissue damage and complications. Therefore, controlling the inflammation response and enhancing the antioxidant capacity of intestinal cells are the key measures to regulate the immune barrier function.
As shown in this figure: the function of physical barrier and immune barrier is more important in the four major intestinal barriers. It also affects the function of microbial barrier and chemical barrier. Based on comprehensive analysis of scholars', it is mentioned that strengthening the function of physical and immune barriers of intestine should focus on solving the problem of intestinal health of suckling piglets.
Again another question comes up: how to enhance the intestinal physical and immune barrier?
Combined with the research results and production practices, we have compiled the strategy of "three external forces & three internal forces". We believe that our efforts to find measures or functional substances that can play a vital role in these six forces will certainly help on the design of an antibiotic-free suckling pig feed.
Firstly, External forces minimize toxic and harmful substances that reach the physical barrier of gut.
Reduce the toxic or harmful substances that bring by the feed with selection and quality control of raw material.
Ensure the digestion and absorption of the nutrients as much as possible with lower nutrient level of formula/reciept; high digestibility of raw materials, such as loosely structured or in vitro pre-digested raw materials; or substances that assist on digestion, such as acidifiers and enzymes.
Reduce the risk of pathogens invading the intestinal epithelium, (bacteriostasis: one of the most classic function of antibiotics).
Secondly, Internal forces maximize the physical and immune barrier of the gut itself.
Promote the proliferation and differentiation of intestinal epithelial cells.
Enhanced tight junction of intestinal epithelial cells with cells and reduced permeability (reduced permeability over the intestinal epithelial surface is the classic action pathway of zinc oxide)
Enhanced anti-inflammatory, antioxidant capacity of intestinal cells (anti-inflammatory is the second classic function of antibiotics).
Comments