Medium and short chain complex fatty acid ester feed additive, preparation method and application

Abstract

The application discloses a medium-short chain composite fatty acid ester feed additive, a preparation method and application, and belongs to the technical field of animal nutrition feed additives. All esterified fatty acid glycerides are used in the application, so that the defects of strong volatility, poor palatability and easy loss in high-temperature processing of free short-chain fatty acids are solved; short-chain glycerides target intestinal mucosa repair and inflammation regulation, medium-chain glycerides provide energy rapidly and inhibit intestinal harmful bacteria, and the two achieve multiple effects of intestinal barrier repair, flora regulation and stress resistance in cooperation. The additive can improve the nutrient digestibility of weaned piglets, optimize intestinal morphology, up-regulate intestinal tight junction genes, reduce intestinal pro-inflammatory factors, increase the abundance of intestinal beneficial lactobacilli, and activate liver energy metabolism; the raw materials of the product are natural, residue-free and drug-resistant, the product is suitable for high-temperature granulation and puffing process of feed, the process is simple, the production cost is low, the product can replace antibiotics and is used for antibiotic-free breeding of weaned piglets and other livestock and poultry, and has wide industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of animal nutrition and feed additive technology, specifically to a medium- and short-chain complex fatty acid ester feed additive, its preparation method, and its application. Background Technology

[0002] Weaning is a crucial stressful stage in piglet production. Piglets weaned around 21 days of age have immature digestive, immune, and intestinal microecologies. They are susceptible to problems such as reduced feed intake, diarrhea, slow growth, impaired intestinal barrier, increased oxidative stress, and exacerbated inflammation due to multiple factors including feed conversion, decreased maternal antibodies, and environmental changes.

[0003] Short-chain fatty acids, such as butyric acid and valerate, serve as important energy sources for intestinal epithelial cells, playing indispensable roles in promoting intestinal development, improving the intestinal barrier, regulating inflammatory responses, and maintaining intestinal microecological balance. Medium-chain triglycerides, composed of medium-chain fatty acids and glycerol, are characterized by rapid digestion and absorption, high energy efficiency, and short metabolic pathways. They can provide a rapid energy source for weaned piglets and also have certain effects in regulating intestinal flora, improving the intestinal environment, and enhancing stress resistance.

[0004] Nevertheless, existing fatty acid feed additives still have certain shortcomings: single esterified short-chain fatty acids have relatively limited functions, with limited comprehensive improvement effects on energy supply, antioxidant capacity, immune regulation, and intestinal health in weaned piglets; adding medium-chain triglycerides alone requires a high dosage, resulting in high costs, and their effects on intestinal barrier repair and short-chain fatty acid signal regulation are insufficient; existing compound products are mostly simple physical mixtures, lacking a systematic design that targets the release characteristics, absorption and metabolism patterns, and functional complementarity of fatty acids of different chain lengths, making it difficult to achieve stable and sustained synergistic effects.

[0005] Therefore, this invention addresses the shortcomings of short-chain fatty acids (SCFAs), which are rapidly absorbed in the stomach and duodenum, have an onset of action of 0-3 hours, a short half-life, and regulate the proximal intestinal and colonic flora, but are also highly volatile, acidic, and prone to burning the stomach wall with a single release. It also addresses the shortcomings of medium-chain fatty acids (MCFAs), which are absorbed in the mid-jejunum, have an onset of action of 3-8 hours, broadly disrupt the cell membranes of Gram-negative bacteria, and provide rapid energy, but whose absorption depends on bile emulsification and whose simultaneous release with SCFAs can compete for transport proteins, reducing the utilization rate of both. This invention utilizes esterified SCFAs and esterified MFAs to significantly reduce the volatility and irritation of fatty acids. A staggered functional ratio is employed to ensure complementary and non-overlapping functions, developing a compound esterified fatty acid suitable for feed that combines the intestinal regulatory effects of SCFAs with the rapid energy supply and microecological regulation effects of MFAs. Summary of the Invention

[0006] The purpose of this invention is to provide a medium- and short-chain complex fatty acid ester feed additive, its preparation method, and its application, in order to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a medium- and short-chain complex fatty acid ester feed additive, wherein the feed additive is composed of a short-chain complex fatty acid glyceride additive and a medium-chain complex fatty acid glyceride additive; wherein the short-chain complex fatty acid glyceride additive is composed of butyrate glyceride and valerate glyceride; and the medium-chain complex fatty acid glyceride additive is composed of caprylic acid glyceride and capric acid glyceride.

[0008] As a preferred technical solution, the short-chain complex fatty acid glyceride additive and the medium-chain complex fatty acid glyceride additive are in the following proportions by mass: 20-40 parts of short-chain complex fatty acid glyceride additive and 60-80 parts of medium-chain complex fatty acid glyceride additive.

[0009] As a preferred technical solution, the mass ratio of butyric acid glyceride to valerate glyceride in the short-chain complex fatty acid glyceride additive is (2-3):1.

[0010] The mass ratio of caprylic acid glyceride to capric acid glyceride in the medium-chain complex fatty acid glyceride additive is 7:3.

[0011] As a preferred technical solution, a carrier is used in the compounding process of the short-chain complex fatty acid glyceride additive and the medium-chain complex fatty acid glyceride additive. The carrier is composed of one or a combination of glucose syrup and silicon dioxide.

[0012] As a preferred technical solution, the carrier accounts for 30-50% of the total mass of the feed additive.

[0013] As a preferred technical solution, the feed additive is in the form of solid granules.

[0014] A method for preparing a medium- and short-chain complex fatty acid ester feed additive includes the following steps: S1. Homogenize butyrate and valerate according to the mass ratio to obtain a mixture. Then add a carrier to the mixture for adsorption and mixing. After mixing evenly, sieve to obtain a short-chain complex fatty acid glyceride additive. S2. Homogenize caprylic acid glyceride and caprylic acid glyceride according to the mass ratio to obtain a mixture. Then add a carrier to the mixture for adsorption and mixing. After mixing evenly, sieve to obtain a medium-chain complex fatty acid glyceride additive. S3. Take the short-chain complex fatty acid glyceride additive obtained in step S1 and the medium-chain complex fatty acid glyceride additive obtained in step S2, mix them evenly according to a certain mass ratio, and then sieve them to obtain the medium- and short-chain complex fatty acid glyceride feed additive.

[0015] As a preferred technical solution, the adsorption mixing temperature in steps S1 and S2 is 20-60℃, and the mixing time is 10-60 min.

[0016] As a preferred technical solution, the mesh size of the sieve used in step S3 is 20 to 100 mesh.

[0017] The application of a medium- and short-chain compound fatty acid ester feed additive in the preparation of antibiotic-free livestock and poultry feed, wherein the addition amount of the medium- and short-chain compound fatty acid ester feed additive in the antibiotic-free livestock and poultry feed is 500 mg / kg to 1500 mg / kg.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. This invention utilizes the simultaneous compounding of two types of short-chain esterified fatty acids, butyrate and valerate, and two types of medium-chain esterified fatty acids, caprylic acid and caprylic acid. Short-chain glycerides can rapidly provide energy to intestinal epithelial cells, repairing intestinal mucosal damage and optimizing the intestinal flora structure. Medium-chain glycerides can exert a broad-spectrum antibacterial effect in the digestive tract of livestock and poultry, inhibiting the proliferation of harmful bacteria such as Escherichia coli and Salmonella. By leveraging the characteristics of short-chain fatty acid glycerides acting on the proximal intestinal and colonic flora regulation, and the characteristics of medium-chain fatty acids acting on the mid-jejunum to broadly disrupt the cell membranes of Gram-negative bacteria and provide rapid energy, the invention achieves complementary functions and action sites among the components, realizing an integrated synergistic effect of "flora regulation + barrier repair + pathogenic bacteria inhibition," with significantly better results than single-fatty acid glyceride products.

[0020] 2. The feed additive of this invention addresses the industry pain points of poor stability, poor palatability, and high volatility of free short-chain fatty acids. Traditional short-chain fatty acids are mostly added in the form of free acids, which have drawbacks such as strong irritating odor, poor palatability, high volatility at high temperatures, poor storage stability, and high feed processing losses. This invention uses esterified fatty acid glycerides, which are non-volatile, odorless, have excellent palatability, and are chemically stable. It effectively avoids many drawbacks of free short-chain fatty acids in feed applications, and significantly improves the retention rate and application stability of the additive in the feed system.

[0021] 3. The feed additive prepared by this invention has strong heat resistance, is suitable for high-temperature granulation processes, has a wide range of processing applications, and has a stable complex esterified fatty acid system. It is not easily decomposed or deactivated during feed conditioning, high-temperature granulation, and extrusion processes. It can stably retain effective components without additional encapsulation treatment and can be widely used in various feed systems such as compound feed, pelleted feed, and premixed feed. Its processing applicability is significantly better than that of traditional fatty acid additives, and it is suitable for large-scale industrial feed production.

[0022] 4. The compound system of this invention can effectively improve the intestinal health of young livestock and poultry, repair intestinal barrier damage caused by weaning stress, maintain intestinal microbial homeostasis, increase animal feed intake and nutrient utilization, improve body growth performance, and has outstanding effects in breeding applications.

[0023] 5. All components of this invention are natural fatty acid esterification products, which have high biosafety, no accumulation in animals, no drug residues, and no drug resistance. They meet the industrial development needs of antibiotic-free and green farming, and can effectively replace antibiotic growth promoters in feed, with broad application prospects.

[0024] 6. The raw materials of this invention are readily available and have good compatibility. The mixing process is simple and can be directly made into powder without the need for complex reaction equipment. The production cost is low and the production efficiency is high, which has excellent industrialization and promotion value. Attached Figure Description

[0025] Figure 1 shows the effect of different esterified fatty acids on the expression levels of genes related to intestinal inflammation in weaned piglets in Experiment 4; Figure 2 shows the HE staining results of different esterified fatty acids on the intestinal morphology of weaned piglets in Experiment 5. Figure 3 Figure 6 shows the effects of different esterified fatty acids on the expression levels of genes related to the jejunal barrier in weaned piglets. Figure 4 Figure 6 shows the effects of different esterified fatty acids on the expression levels of genes related to the ileal barrier in weaned piglets. Figure 5 Figure 7 shows the effect of different esterified fatty acids on the expression levels of genes related to liver energy metabolism in weaned piglets in Experiment 7; Figure 6 shows the results of the α-diversity analysis of jejunal microorganisms in Experiment 8; Figure 7 shows the results of the PCoA analysis of β-diversity of jejunal microorganisms in Experiment 8; Figure 8 shows the results of the classification and composition analysis of jejunal microbial communities in Experiment 8. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example

[0028] This embodiment provides a method for preparing a medium- and short-chain complex fatty acid ester feed additive, which specifically includes the following steps:

[0029] S1. Homogenize 310 g of butyric acid glyceride and 140 g of valerate glyceride to obtain a mixture. Then add 550 g of silicon dioxide to the mixture, mix evenly, and pass through an 80-mesh sieve to obtain a short-chain complex fatty acid glyceride additive. S2. Homogenize 490 g of caprylic glyceride and 210 g of capric glyceride to obtain a mixture. Then add 150 g of silicon dioxide and 150 g of glucose syrup to the mixture, mix evenly, and pass through an 80-mesh sieve to obtain a medium-chain complex fatty acid glyceride additive. S3. Take the short-chain complex fatty acid glyceride additive prepared in step S1 and the medium-chain complex fatty acid glyceride additive prepared in step S2, mix them evenly in a 1:2 ratio, and pass them through an 80-mesh sieve to obtain a medium- and short-chain complex fatty acid glyceride feed additive. After preparation, short-chain complex fatty acid glyceride additive, medium-chain complex fatty acid glyceride additive, and medium- and short-chain complex fatty acid glyceride feed additive are obtained.

[0030] A comparative experiment was conducted on the feed additive prepared in this embodiment. The specific experimental method is as follows: Thirty-two healthy weaned piglets aged 21 days were selected and randomly divided into four groups: the normal control group (NC), the short-chain fatty acid group (T1), the medium- and short-chain complex fatty acid group (T2), and the medium-chain fatty acid group (T3), with eight piglets in each group. The piglets were raised from 21 to 49 days of age. During the feeding period, the NC group was fed only the basal diet, the T1 group was fed the basal diet plus 1000 mg / kg of short-chain complex fatty acid glycerides, the T2 group was fed the basal diet plus 500 mg / kg of medium- and short-chain complex fatty acid glycerides, and the T3 group was fed the basal diet plus 2000 mg / kg of medium-chain complex fatty acid glycerides. At 49 days of age, blood samples were collected from the piglets, and their growth performance was statistically analyzed. The piglets were euthanized, and tissue samples were collected for biochemical index determination. Based on the biochemical index determination results, the following exploratory experiments were conducted.

[0031] Experiment 1: Investigating the effects of different esterified fatty acids on the growth performance of weaned piglets.

[0032] Experimental results: As shown in Table 1, compared with the normal control group (NC), the medium-chain fatty acid group (T3) significantly increased the average daily feed intake (ADFI) (P<0.05), indicating that the medium-chain fatty acid group has a positive effect on improving growth performance.

[0033] Table 1 shows the effects of different esterified fatty acids on the growth performance of weaned piglets. Note: Different superscript letters in the same line indicate significant differences (P < 0.05).

[0034] Experiment 2: Investigating the effects of different esterified fatty acids on the nutrient digestibility of weaned piglets.

[0035] Experimental results: As shown in Table 2 below, compared with the normal control group (NC), the short-chain fatty acid group (T1), the medium-short-chain complex fatty acid group (T2), and the medium-chain fatty acid group (T3) showed significantly higher crude fat nutrient digestibility (P<0.05) in the short-chain fatty acid group (T1) and the medium-short-chain complex fatty acid group (T2), indicating that the short-chain fatty acid group (T1) and the medium-short-chain complex fatty acid group (T2) have a promoting effect on the apparent digestibility of crude fat in piglets.

[0036] Table 2 shows the effects of different esterified fatty acids on the apparent nutrient digestibility of weaned piglets. Note: Different superscript letters in the same line indicate significant differences (P < 0.05).

[0037] Experiment 3: Investigating the effects of different esterified fatty acids on the serum and intestinal cytokine levels in weaned piglets.

[0038] Experimental Results: As shown in Table 3, compared with the normal control group (NC), the medium- and short-chain fatty acid complex group (T2) showed a significant decrease in the interleukin-1β (IL-1β) content in the jejunal tumors of piglets (P<0.05). Meanwhile, the short-chain fatty acid group (T1), the medium- and short-chain fatty acid complex group (T2), and the medium-chain fatty acid group (T3) all significantly increased the content of interleukin-10 (IL10) in the ileum of piglets (P<0.05). Therefore, medium- and short-chain fatty acid ester additives can effectively improve the intestinal health of young livestock and poultry and repair intestinal barrier damage caused by weaning stress.

[0039] Table 3 shows the effects of different esterified fatty acids on the serum and intestinal cytokine levels in weaned piglets (pg / mL). Note: Different superscript letters in the same line indicate significant differences (P < 0.05).

[0040] Experiment 4: Investigating the effects of different esterified fatty acids on the expression levels of genes related to ileal inflammation in weaned piglets.

[0041] Experimental results: as attached Figure 1 As shown, compared with the normal control group (NC), the expression level of interleukin-6 (IL-6) gene in the jejunal mucosa of piglets in the short-chain fatty acid group (T1), medium-short chain complex fatty acid group (T2), and medium-chain fatty acid group (T3) was significantly decreased (P<0.05), indicating that esterified fatty acids can inhibit intestinal inflammation by downregulating the expression of the pro-inflammatory factor interleukin (IL-6) and exhibit good anti-inflammatory effects.

[0042] Experiment 5: Investigating the effects of different esterified fatty acids on the intestinal morphology of weaned piglets.

[0043] Experimental results: as attached Figure 2 As shown in the HE staining images of jejunal and ileal sections, the intestinal morphology of each group was normal, with neatly arranged villi and intact structure. The intestinal villi development of the medium- and short-chain fatty acid (T2) group and the medium-chain fatty acid (T3) group was superior to that of the normal control group (NC), with more neat and dense villi arrangement. The measurement results of intestinal morphology are shown in Table 4 below. Compared with the normal control group (NC), the medium- and short-chain fatty acid (T2) group and the medium-chain fatty acid (T3) group significantly increased the jejunal villi height and villus-to-crypt ratio in piglets (P<0.05). The medium- and short-chain fatty acid (T2) group significantly increased the ileal villi height and villus-to-crypt ratio in piglets (P<0.05) and significantly decreased the ileal crypt depth (P<0.05). The medium-chain fatty acid (T3) group significantly increased the ileal villi height in piglets (P<0.05). The results showed that both medium- and short-chain fatty acids and medium-chain fatty acids could improve the intestinal health of piglets by optimizing intestinal morphology. Among them, medium- and short-chain fatty acids had a more comprehensive and prominent effect on improving the intestinal health of piglets, and had a more obvious advantage in improving ileal intestinal function.

[0044] Table 4 shows the effects of different esterified fatty acids on the intestinal morphology of weaned piglets (pg / mL). Note: Different superscript letters in the same line indicate significant differences (P < 0.05).

[0045] Experiment 6: Investigating the effects of different esterified fatty acids on the expression levels of intestinal barrier-related genes in weaned piglets. Experimental results: as attached Figure 3 , 4As shown, compared with the normal control group (NC), the expression level of the closing protein (OCLN) gene in the jejunal mucosa of piglets in the medium- and short-chain fatty acid (T2) group (T3) was significantly upregulated (P<0.05), while the expression level of the band-occlusion protein 1 (ZO-1) gene in the ileal mucosa of piglets in the medium-chain fatty acid group (T3) was significantly upregulated (P<0.05). This indicates that both medium- and short-chain fatty acids and medium-chain fatty acids can enhance the jejunal intestinal barrier function by upregulating the expression of closing protein (OCLN). Among them, medium-chain fatty acids can also simultaneously upregulate the expression of ileal (ZO-1), further improving the barrier integrity of the ileum.

[0046] Experiment 7: Investigating the effects of different esterified fatty acids on the liver energy metabolism function of weaned piglets.

[0047] Experimental results: as attached Figure 5 As shown, compared with the normal control group (NC), the G6PC gene in the liver of piglets in the short-chain fatty acid group (T1), medium-short chain complex fatty acid group (T2), and medium-chain fatty acid group (T3) was significantly upregulated (P<0.05), indicating that the complex fatty acid activated the hepatic gluconeogenesis pathway to maintain blood glucose homeostasis.

[0048] Experiment 8: Investigating the effects of different esterified fatty acids on the composition and diversity of microbial composition in the jejunal chyme of weaned piglets.

[0049] Experimental results: The α-diversity of jejunal microbiota in weaned piglets is shown in the attached figure. Figure 6 As shown, the ACE index of the medium- and short-chain fatty acid group (T2) in the jejunal microbiota was significantly higher than that of the medium-chain fatty acid group (T3) (P < 0.05). Figure 6 A) indicates that medium- and short-chain fatty acids have a higher richness of gut microbiota in piglets.

[0050] β-diversity of jejunal microbiota in weaned piglets, such as Figure 7 As shown, principal coordinate analysis (PCoA) results indicate that, at the genus level, there is a significant separation between the medium- and short-chain fatty acid complex group (T2) and the normal control group (NC) in the jejunal microbiota of piglets, forming two distinct communities. Figure 7 B).

[0051] The taxonomic composition of the jejunal microbiota at the phylum and genus levels is as follows: Figure 8 As shown. At the phylum level, Bacillota, Pseudomonadota, and Cyanobacteriota are the major components of the jejunal microbiota in weaned piglets. Figure 8A) Compared with the normal control group (NC), there were no significant differences in the relative abundance of major bacterial groups in the jejunal digesta of weaned piglets in the short-chain fatty acid group (T1), medium-short-chain complex fatty acid group (T2), and medium-chain fatty acid group (T3) (P>0.05). At the genus level, Lactobacillus, Streptococcus, and Metamycoplasma are the major components of the jejunal microbiota of weaned piglets. Figure 8 Compared with the control group, the relative abundance of Lactobacillus in the jejunum of piglets in the medium- and short-chain fatty acid group (T2) and the medium-chain fatty acid group (T3) was significantly increased (P < 0.05). Figure 8 F). Lactobacillus is a core beneficial lactic acid bacterium in the gut. Increased abundance of Lactobacillus can improve the integrity of the intestinal barrier in piglets, inhibit the growth of harmful bacteria, and promote the digestion and utilization of nutrients. This indicates that medium- and short-chain fatty acids and medium-chain fatty acids can significantly increase the relative abundance of Lactobacillus in the piglet gut, which is an important microbial mechanism for improving intestinal health.

[0052] Results analysis shows that, based on the results of experiments 1-8: Compared with the normal control group (NC), the short-chain fatty acid group (T1) has the advantages of significantly improving the apparent digestibility of crude fat in piglets, inhibiting intestinal inflammation, and maintaining blood glucose homeostasis.

[0053] Compared with the normal control group (NC), the medium- and short-chain fatty acid complex group (T2) has the advantages of significantly improving the apparent digestibility of crude fat in piglets, promoting growth, bidirectionally regulating and reducing small intestinal inflammation, improving intestinal morphology and physical barrier function, maintaining blood glucose homeostasis and reshaping intestinal flora homeostasis.

[0054] Compared with the normal control group (NC), the medium-chain fatty acid group (T3) has the advantages of improving growth performance, alleviating intestinal inflammation, maintaining blood glucose homeostasis and optimizing the structure of beneficial intestinal flora.

[0055] The superiority of the medium- and short-chain fatty acid complex group (T2) over the short-chain fatty acid group (T1) and the medium-chain fatty acid group (T3) is as follows: (1) Inflammation regulation dimension: The medium- and short-chain fatty acid group (T2) can significantly reduce the jejunal pro-inflammatory factor IL-1β, thereby inhibiting local acute inflammation in the jejunum; the short-chain fatty acid group (T1) and the medium-chain fatty acid group (T3) have no effect on downregulating jejunal IL-1β. (2) Improvement of intestinal morphology: The medium- and short-chain fatty acid complex group (T2) can significantly reduce the ileal crypt depth and increase the ileal villus-crypt ratio; the medium-chain fatty acid group (T3) only increases the height of the ileal villus and cannot improve the crypt depth and villus-crypt ratio. (3) Intestinal microbiota richness: The ACE index of jejunal microbiota in the medium-short chain fatty acid group (T2) was significantly higher than that in the medium chain fatty acid group (T3), and the microbiota species richness was better than that in the single medium chain fatty acid group.

[0056] In summary, it can be seen that short-chain fatty acid additives only act on fat digestion, basic anti-inflammation, and liver metabolism, without improving intestinal morphology, barrier function, and microbiota. Medium-chain fatty acid additives focus on promoting food intake, improving the jejunal and ileal barrier function, and providing localized improvements in intestinal morphology. Medium- and short-chain fatty acid glycerides simultaneously address fat digestion, dual anti-inflammation in the jejunum and ileum, optimization of the entire intestinal morphology, strengthening of the jejunal barrier, enhancement of microbiota abundance, and liver glucose metabolism, providing a more comprehensive regulatory dimension and demonstrating significant advantages in improving ileal intestinal function.

[0057] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A medium- and short-chain complex fatty acid ester feed additive, characterized in that, The feed additive is composed of a combination of short-chain complex fatty acid glycerides and medium-chain complex fatty acid glycerides. The short-chain complex fatty acid glyceride additive is composed of butyrate and valerate; the medium-chain complex fatty acid glyceride additive is composed of caprylic acid and caprylic acid.

2. The medium-short chain compound fatty acid ester feed additive according to claim 1, characterized in that, The short-chain complex fatty acid glycerides additive and the medium-chain complex fatty acid glycerides additive are in the following proportions by weight: 20-40 parts of short-chain complex fatty acid glycerides additive and 60-80 parts of medium-chain complex fatty acid glycerides additive.

3. The medium-short chain compound fatty acid ester feed additive according to claim 1, characterized in that, The mass ratio of butyrate glyceryl ester to valerate glyceryl ester in the short-chain complex fatty acid glyceryl ester additive is (2-3):1; The mass ratio of caprylic acid glyceride to capric acid glyceride in the medium-chain complex fatty acid glyceride additive is 7:

3.

4. The medium-short chain compound fatty acid ester feed additive according to claim 1, characterized in that, The short-chain complex fatty acid glyceride additive and the medium-chain complex fatty acid glyceride additive are compounded using a carrier, which is composed of one or a combination of glucose syrup and silicon dioxide.

5. The medium-short chain compound fatty acid ester feed additive according to claim 4, characterized in that, The carrier accounts for 30-50% of the total mass of the feed additive.

6. The medium-short chain compound fatty acid ester feed additive according to claim 1, characterized in that, The feed additive is in the form of solid granules.

7. A method for preparing a medium-short chain complex fatty acid ester feed additive according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Homogenize butyrate and valerate according to the mass ratio to obtain a mixture. Then add a carrier to the mixture for adsorption and mixing. After mixing evenly, sieve to obtain a short-chain complex fatty acid glyceride additive. S2. Homogenize caprylic acid glyceride and caprylic acid glyceride according to the mass ratio to obtain a mixture. Then add a carrier to the mixture for adsorption and mixing. After mixing evenly, sieve to obtain a medium-chain complex fatty acid glyceride additive. S3. Take the short-chain complex fatty acid glyceride additive obtained in step S1 and the medium-chain complex fatty acid glyceride additive obtained in step S2, mix them evenly according to a certain mass ratio, and then sieve them to obtain the medium- and short-chain complex fatty acid glyceride feed additive.

8. The method for preparing a medium- and short-chain complex fatty acid ester feed additive according to claim 7, characterized in that, The adsorption mixing temperature in steps S1 and S2 is 20–60°C, and the mixing time is 10–60 min.

9. The method for preparing a medium- and short-chain complex fatty acid ester feed additive according to claim 7, characterized in that, The sieve mesh number for sieving in step S3 is 20 to 100 mesh.

10. The application of the medium-short chain complex fatty acid ester feed additive according to any one of claims 1 to 9 in the preparation of antibiotic-free livestock and poultry feed, characterized in that, The medium- and short-chain complex fatty acid ester feed additive is added at a rate of 500 mg / kg to 1500 mg / kg in antibiotic-free livestock and poultry feed.

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