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Wang Junjun: Professor and Vice Dean of college of animal science and technology, China Agricultural University Deputy Director of the Sterile Animal Committee of the Chinese Society for Laboratory Animals
Introduction: Professor of College of Animal Science and Technology, China Agricultural University, Assistant Director of feed industry center of the Ministry of Agriculture / Director of Nutrition and Reproduction Research Office, mainly engaged in developmental physiology and nutrition optimization of low-birth heavy pigs, nutrition monitoring and precision supply research of pigs. He was selected as a leading talent in scientific and technological innovation of the 10,000-person plan, a young Yangtze River scholar of the Ministry of Education, an outstanding youth science fund of the Foundation Committee, and a young and middle-aged scientific and technological innovation leading talent of the Ministry of Science and Technology, and won the 14th China Youth Science and Technology Award. He has published more than 60 papers in journals such as the Journal of Nutrition and has been cited more than 2,000 times. Serves on the editorial boards of british journals of Nutrition, Journal of Animal Science and others.
Hello audience, I am Wang Junjun from China Agricultural University.
It is a great honor to be invited by the Enthusiastic Gut Research Institute to share and exchange "Digestive Fermentation Kinetic Balance and Efficient Utilization of Nutrients" with you.
As the saying goes, "the country is based on the people, the people take food as the sky, and food takes safety as the first." Food security is a major livelihood issue.
The theme of this year's Food Security Day is: Firmly hold China's rice bowl and build global food security together.
Since the founding of the People's Republic of China, the dietary structure of the Chinese has undergone tremendous changes, and the demand has changed from eating well to eating well.
According to data from the National Bureau of Statistics, the per capita grain consumption of Chinese residents has decreased significantly in recent years, and the consumption of meat, eggs and milk has doubled, and the annual meat consumption has reached more than 80 million tons.
The increase in demand for livestock products such as meat, eggs and milk has led to a large number of grains and their processing by-products being used as feed, and the gap has increased year by year, and protein resources such as soybeans are heavily dependent on imports. Food security is epitomized by the safety of feed and food, which has created a situation in which people and livestock compete for food.
China is the world's largest pig country and pork consumption country, nearly half of the world's pigs are raised in China, and the proportion of pork consumption of Chinese residents in meat consumption has reached 62%. Therefore, pig food is safe in the world, and pork and grain are safe in the world.
In the past two years, the reduction in pig output caused by African swine fever, the rise in pig prices and the rise in the CPI index (consumer price index) must have a deep understanding.
But what I want to focus on here is that the food of pigs, that is, pig feed, is safe in the world. Pig feed accounts for 43% of China's compound feed, which is an important factor in feed grain and food security.
However, the precise preparation of pig feed in China is faced with many types of feed raw materials, and the same feed raw materials have caused a large variation in their nutritional value due to the variation of factors such as variety, place of origin, processing technology and so on.
In terms of pigs, There are diverse pig breeds in China, and the breeding level, environmental facilities and nutritional needs of pigs are also different.
Our team found in the course of an earlier study of 260 maize samples that the difference between the maximum and minimum values of their effective energy values can reach nearly 700 kcal per kilogram, and the coefficient of variation can be as high as 5.6%.
Therefore, how to accurately grasp the effective nutrient variation of feed raw materials and the variation of pig nutrient requirements in production is the key to accurate formulation.
In addition to grasping the problem of variation, it is also necessary to consider the problem of waste of excretion.
For example, a portion of the energy ingested is excreted through fecal urine, and this energy does not contribute to animal growth.
Therefore, in the process of evaluating feed raw materials, it is necessary to consider the energy lost through heat consumption and various gas emissions, so as to use the index system of digestion energy, metabolic energy and net energy.
To this end, we have built the corresponding net energy evaluation equipment, and on the basis of a series of evaluations, we have realized the upgrading of the effective energy value of pigs from digestion energy and metabolic energy to the net energy system.
Unlike energy nutrition, the evaluation of protein nutrition needs to consider the effects of large bowel fermentation.
After the proteins that are not digested and absorbed in the small intestine enter the large intestine, they are fermented by microorganisms to produce biological amines, indole and other substances, which not only cannot be reabsorbed into the body to deposit proteins, but often have toxic side effects.
Therefore, the evaluation of protein nutrition should focus on its digestion and absorption in the small intestine.
We collect chyrus ileum by installing a fistula at the end of the ileum to evaluate and calculate its utilization efficiency in the small intestine stage, thereby calculating the digestibility of its proteins or amino acids.
In addition, recent advances in amino acid balance research and crystalline amino acid production technology have made it possible to formulate and promote low-protein diets based on ideal amino acid patterns.
This new balancing technique can reduce the level of crude protein in pig diets by 2 to 4 percentage points, thereby reducing the use of protein raw materials, reducing feed formulation costs, reducing nitrogen emissions, and improving intestinal health by reducing the toxic side effects of fermentation of large intestinal proteins.
In order to dynamically estimate the nutrient requirements of pigs, modelling studies based on experimental data are important.
Based on the summary of long-term research, our team has established a dynamic estimation equation based on body weight, daily weight gain, maintenance, growth and their nutrient requirements for fat and protein deposition, which is convenient for dynamic estimation of the demand values in the set formulation in production.
Considering the diversity and complexity of feed raw materials, the establishment of their dynamic evaluation models requires greater workload.
Based on long-term and large-scale evaluations, our team explored the establishment of predictive equations and prediction models based on simple chemical combination analysis, or the effective energy of near-infrared spectral scanning, and ileal amino acid digestibility.
We have also integrated the above research results to form FeedSaaS, a Chinese pig feed nutrition big data platform that is easy to promote and apply, integrate our MAFIC feed raw material database, the new version of pig nutrition requirements, with the dynamic model as the core, and provide a solution for achieving precision nutrition and rapid formulation before entering the pig's mouth.
However, in addition to the precise formula, the actual nutritional satisfaction of pigs may also be affected by the accuracy of dietary allocation, the combination effect between raw materials, the physiological state variation of pigs, and the amount of food intake.
Therefore, how to carry out nutritional evaluation after pig feeding is also very important.
Considering the synthesis of plasma samples and the correlation between metabolic groups and dietary nutrients, as well as growth performance, we selected plasma samples to explore the possibility of evaluating the nutritional status of pigs based on plasma metabolic markers.
Our protocol is to feed pigs with diets with different nutrient levels, collect blood to study the metabolic markers associated with specific nutrient levels in their plasma, and build spectral recognition models and estimation equations on this basis to evaluate the nutritional status of specific pigs and optimize feedback.
This is our energy profile prediction equation based on the systematic identification of metabolic markers associated with dietary energy levels in pig plasma.
On this basis, a spectral recognition model of energy level and protein level was established, and the evaluation and monitoring of pig nutritional status based on plasma metabolic markers was realized.
In addition, the same nutritional parameters were found in the course of the study, and different growth properties may be produced when the raw material and nutrient substrate are largely variable.
For example, when using different proportions of carbohydrates and fats as energy sources, pigs have differences in daily weight gain and material-to-weight ratio.
The reason may be related to the rate of digestion and release of energy substrates such as glucose and the degree of matching between them and the release and absorption of amino acids.
This also occurs in low-protein diets.
In addition to being used for muscle protein deposition, amino acids are also metabolized by their gut cells and their gut microbes as they pass through the digestive tract.
Interestingly, when using a balanced diet that lowers protein levels and uses free crystalline amino acids, its amino acids are quite different from regular diets in terms of absorption into the bloodstream.
This amino acid, which is rapidly absorbed into the bloodstream, is more oxidized and metabolized, thereby reducing its efficiency for protein deposition. Therefore, new energy substrate balance patterns need to be considered for low-protein diets.
In comparing the plasma metabolome at different time points after feeding pigs in two feeds, conventional diet and starch-casein pure diet, we found that pure diet will be earlier and faster in glucose and amino acid release and absorption. However, from 2 hours after a meal, the ability to continuously supply glucose and amino acids is significantly reduced.
This dynamic change in space-time also suggests that in the evaluation process of feed nutritional value, there may be another dimension of work that is missing, that is, its digestion and fermentation kinetics in the intestine.
Moreover, this problem of space-time dynamic equilibrium exists not only in feed raw materials, but also in the variation of animals with different digestive and fermentation characteristics.
We used the same formula diet to feed normal pigs in equal proportions to body weight and pigs with intrauterine growth restriction during pregnancy and found that there was a difference in nutrient absorption in the portal vein.
Further analysis of its digestion in the small intestine and the fermentation of the large intestine found that the digestion capacity of the small intestine was relatively poor, while the fermentation activity of the large intestine was relatively high.
After cross-fermentation using its corresponding ileal chyme and cecum microorganisms, it was found that the cecum microbial fermentation capacity of IUGR (intrauterine growth restriction) pigs was actually weak, and its relatively high fermentation activity was due to the richness of nutrients at the end of the ileum caused by poor digestion capacity of the small intestine.
Therefore, it is a more cost-effective strategy to achieve relatively full digestion and utilization of nutrients in the small intestine through regulation.
Of course, from the perspective of carbohydrates or fiber nutrition, the contribution of large intestinal microorganisms and their activities to feed efficiency cannot be ignored.
Through automatic feeding and animal growth performance collection devices, we screened pigs with high and low feed efficiency. Studies have found differences in their larger intestinal microbes, the content of fibroblast bacteria and the production of propionic acid is relatively high. And when using its feces to ferment the same fibrous components, its fermentation capacity is also stronger.
Therefore, microbial colonization intervention is also a good nutritional intervention strategy.
To this end, we are considering the digestion kinetics of the systematic evaluation of raw materials, especially the release kinetic curve of glucose and amino acids, and the fermentation kinetic curve of the digestion residue of the small intestine, which is of great significance for achieving spatio-temporal dynamic balance and achieving synchronous release and absorption of glucose and amino acids during dietary preparation.
After mapping the digestion and fermentation kinetic curves of the relevant raw materials, we will find the main time points of their differences and focus on them.
The most appropriate glucose and amino acid release modes are obtained and confirmed through animal experiments, thus laying the foundation for increasing the equilibrium parameters of digestion and fermentation kinetics in the process of dietary preparation.
However, it is often difficult to match the required digestion and fermentation kinetic parameters through the combination of raw materials.
In most cases, we involve the pre-processing and pre-treatment of raw materials, including changing their digestion and fermentation characteristics.
Such interventions involve the combination of raw materials, the modification of raw materials, and the microbial intervention of receptors.
In the transformation of raw materials, we may achieve kinetic regulation of digestion and fermentation through some physical methods, chemical methods and biological methods, including modulation, puffing, alkalinization, oxidation, microbial fermentation, enzymatic digestion, bacteriomatic enzyme synergy and other means.
In terms of microbial interventions, considering the need for its total intestinal colonization interventions, we recently studied total intestinal microbial transplantation with a combination of jejunum, ileum, cecum and colonic microorganisms, compared with fecal microbial transplantation, in terms of receptor microbial colonization interventions.
When each intestinal segment of microorganisms is transplanted individually, it is more likely to colonize the intestinal segment of its origin; the whole intestinal microbiome transplantation has a better effect on colonization interventions for each intestinal segment of microorganisms, especially small intestinal microorganisms, and will target the structure and function of the corresponding intestinal segment.
It is suggested that for nutrition-related research and applications, we can choose a full-gut microbiome transplant whenever possible.
This creates another problem, as we cannot easily obtain chyme and their microbes of the jejunum, ileum, cecum, and colon as easily as we do with feces. Then a strategy for intestinal microbiome culture needs to be considered.
On the basis of the systematic analysis of the chyme nutrient composition of each intestinal segment, we optimized and improved the commercial pig microbiome medium, and initially established the incubation conditions of the microbiome of the cecum and colon, which can obtain the microbial source for intervention at a relatively low cost.
As just mentioned, the study of establishing the dynamic curve of digestion and fermentation of each raw material, determining the optimal combination goal, and realizing the spatio-temporal balance of digestion and fermentation through raw material modification and microbiome transplantation.
However, in production practice, how to quickly obtain the digestion and fermentation kinetic parameters of raw materials has become particularly important. It is not possible to perform digestion and fermentation kinetic evaluation experiments on the relevant raw materials every time.
Therefore, this is also the work we are working on to establish a prediction model of raw material digestion and fermentation kinetic parameters based on near-infrared spectroscopy.
In the later stage, the raw materials can be scanned by near-infrared and directly produce the characteristics of their digestion and fermentation kinetics, thus laying the corresponding technical means for the preparation of balanced diets for digestion and fermentation kinetics.
To summarize my report today, we have established a corresponding dynamic prediction model for the large variation in the nutritional value of feed raw materials and pig nutrient requirements, and integrated the formation of FeedSaaS, a big data platform for feed in China.
Based on the nutritional evaluation and feedback optimization after feeding, a nutritional status profile recognition model based on plasma metabolome was established.
Based on the digestion and fermentation kinetics of raw materials and pigs in the process of digestion and utilization, and how to carry out the spatio-temporal release and absorption of nutrients such as glucose and amino acids, some exploration work has been carried out, including raw material combination, raw material transformation, microbial transformation and effective microbiome culture.
I hope that everyone will criticize and correct, and also welcome various forms of cooperative research and application promotion.
That concludes my report. Thank you to the Foundation Committee, the Ministry of Science and Technology and other projects for their support and the dedication of the team.
Thanks to the Warm Gut Institute, thank you.