What Are the Uses of Mannan Oligo Saccharide in Animal Feeding?

Veterinary antibiotics have long played a vital role in preventing animal diseases and promoting animal growth. However, the extensive and widespread use of antibiotics in food animals has led to two major problems: antibiotic residues and the development of bacterial resistance. Antibiotic residues affect food safety and public health, while increased bacterial resistance threatens medical resources for humans.

At the China Feed Development Forum held on April 16, 2018, a relevant person from the Ministry of Agriculture and Rural Affairs stated that drug feed additives would be completely withdrawn by 2020. At the same time, the Ministry of Agriculture and Rural Affairs announced the Notice on Launching the Pilot Work of Reducing the Use of Veterinary Antibiotics from 2018 to 2021, which clearly defines the timetable for reducing and limiting the use of antibiotics in breeding.

In the context of comprehensive antimicrobial resistance reduction or restriction, safe and efficient green feed additives have become one of the current research and development hotspots. A large number of studies have shown that as a new type of feed additive, mannan-oligosaccharides have the functions of enhancing immunity, regulating the gastrointestinal environment, and improving the production performance of livestock and poultry, and have a wide range of applications in animal husbandry production. This paper reviews the biological effects of mannan-oligosaccharides and their application in animal husbandry production, providing a theoretical reference for the scientific application of mannan-oligosaccharides.

1 Biological effects of mannan-oligosaccharides

1.1 Enhancing the immune system

Mannan-oligosaccharides are immunogenic and can enhance the immune response to antigens, thereby strengthening the humoral and cellular immune systems of animals. As an adjuvant for exogenous antigens, mannan-oligosaccharides can bind to the surfaces of certain toxins, viruses and eukaryotic cells, slowing antigen uptake and increasing antigen potency. Once mannan-oligosaccharides enter the body, they stimulate the liver to secrete mannan-oligosaccharide-binding proteins. These proteins can bind to the bacterial cell wall and trigger a series of complement reactions, thereby triggering an immune response. The immune response is triggered by cells, and T cells play an important role.

The proliferation and differentiation of T cells requires the participation of interleukin-2, and the concentration of interleukin-2 in cells increases with the addition of mannan-oligosaccharides [1]. In addition, mannan-oligosaccharides enhance the activity of IFN, a cytokine secreted by activated T cells, which attracts white blood cells, body fluids and proteins to the site of infection and activates the phagocytic activity of macrophages. Mannan-oligosaccharides can promote the proliferation of some beneficial bacteria such as Bifidobacterium, which can increase the body's antibody levels and thus enhance the body's immune function.

1.2 Regulating the gastrointestinal environment of animals

Mannan-oligosaccharides not only promote the growth of beneficial bacteria such as bifidobacteria and some lactobacilli, but also inhibit the reproduction of harmful bacteria such as Escherichia coli, Salmonella typhimurium and Clostridium botulinum. They can also adsorb harmful pathogens and improve the intestinal environment. Most pathogenic bacteria are able to colonize the epithelial cells of the animal intestine because they recognize and bind to specific sugar molecules on the animal intestinal epithelial cells through exogenous lectins on their own cell surfaces, and then develop and reproduce, which in turn leads to intestinal diseases.

Mannan-oligosaccharides can bind to the exogenous lectin of Escherichia coli, so that the intestinal pathogenic bacteria cannot bind to the specific sugar molecules on the surface of the intestinal epithelial cells, thus achieving the purpose of preventing the pathogenic bacteria from colonizing and reproducing in the gastrointestinal tract. When a certain amount of mannan-oligosaccharides is present in the intestine, it can carry the pathogenic bacteria through the intestine, and the chance of the pathogenic bacteria colonizing in the intestine is greatly reduced. While improving the intestinal microecological environment, it is also more conducive to intestinal digestion and absorption.

1.3 Adsorption of certain mycotoxins

In recent years, a large number of studies have shown that mannan oligosaccharides can physically adsorb or directly bind mycotoxins without affecting the nutritional composition of the feed. The binding rates of mannan oligosaccharides to aflatoxin, zearalenone and ochratoxin are 82.5%, 51.6% and 26.4% respectively, of which the binding capacity of aflatoxin mainly depends on the pH, the concentration of the toxin and the amount of mannan-oligosaccharide additive used. The binding capacity at pH 6.8 was >pH 4.5, and the binding capacity also tended to increase when the amount of mannan-oligosaccharide added was between 500 and 1,000 mg·kg-1.

1.4 Improving livestock and poultry performance

The addition of mannan-oligosaccharides can inhibit the reproduction of pathogenic and putrefactive bacteria in the gastrointestinal tract, reduce the production of toxins, amines, ammonia, indoles and other toxic and harmful metabolites, and reduce animal morbidity. Mannan-oligosaccharides can promote the proliferation of beneficial bacteria, and some beneficial bacteria can produce substances essential to the body, such as bifidobacteria, which can synthesize vitamins such as VB1 and VB12 and amino acids in the intestine. In addition, the acidic substances produced by oligosaccharide fermentation can increase the solubility of calcium compounds in the gastrointestinal tract, making it easier for the intestines to absorb calcium. The balance of intestinal flora, the animal's feed intake, feed digestibility, etc., will all increase to varying degrees, and production performance will subsequently improve.

2 Application of mannan-oligosaccharides in animal husbandry

2.1 Pigs

There have been many reports of trials on pigs using mannan-oligosaccharides, and the conclusions drawn are also different. Studies have shown that adding mannan-oligosaccharides to the diet can increase body weight gain and feed intake in pigs at different stages, improve feed conversion rate, and have a positive effect on production performance. Adding 0.2% mannan-oligosaccharides to the diet of pregnant sows significantly increased the birth weight and weaning weight of piglets, and significantly reduced the mortality rate of piglets before weaning.

The possible reason is that adding mannan-oligosaccharides to the diet of lactating sows improves the composition of immune . The addition of 0.2% mannan-oligosaccharides to the lactating sow diet can effectively shorten the interval between estrus, increase the birth weight of the litter and the weaning weight of the piglets, and significantly reduce the pre-weaning mortality rate of the piglets [1]. Adding 480 mg·kg-1 mannan-oligosaccharides to the diet of fattening pigs can increase daily weight gain, reduce feed conversion ratio and diarrhea rate, etc. When used in combination with chlortetracycline, it can increase average daily weight gain, reduce average daily feed intake and feed conversion ratio, and also has a certain effect on improving meat quality and flavor.

In piglets aged 1–49 days, the addition of 0.2% mannan-oligosaccharides to the diet can increase daily weight gain and feed conversion ratio. When fed together with Clostridium butyricum, piglets show an increase in daily weight gain, feed conversion ratio and crude fiber digestibility [2]. In piglets weaned at 28 days of age, the addition of 0.1% and 0 .2% can significantly inhibit the proliferation of Escherichia coli in the colon, cecum and rectum, and increase the concentration of Lactobacillus in the cecum. Feeding 35-day-old weaned piglets a basal diet containing 0.3% mannan-oligosaccharides can significantly inhibit the growth of Escherichia coli in the piglets' intestines, reduce the competition between Escherichia coli and beneficial bacteria such as Lactobacillus and Bifidobacterium in the intestines bifidobacteria and other beneficial bacteria, thereby maintaining the balance of the digestive tract flora in weaned piglets. Adding 0.4% mannan-oligosaccharides to the diet of weaned piglets can effectively reduce the incidence of diarrhea, and blood glucose, triglycerides, total cholesterol, low-density lipoprotein and very low-density lipoprotein levels are all reduced to varying degrees [3].

2.2 Poultry

The addition of 50 mg·kg-1 mannan-oligosaccharides to the diet of broiler chickens can improve growth performance and health status; promote the development of immune organs; improve immunity and antioxidant capacity; and significantly increase the activity of catalase and superoxide dismutase. There is also a trend of increase in the activity of glutathione peroxidase and total antioxidant capacity [4]. Broiler chickens: Adding 0.1% mannan-oligosaccharides to the diet can promote the growth performance of broiler chickens, improve feed utilization, improve the intestinal microecological environment and enhance the immune function of the body. The combination of mannan-oligosaccharides and organic selenium can improve production performance and immune function. Laying hens: The addition of 1 or 1.5 g·kg-1 mannan-oligosaccharides to the diet of laying hens improves their performance and feed conversion efficiency. The improvement in performance may be due to an increase in nutrient digestibility in the ileum and a decrease in the number of pathogenic bacteria in the intestine [5-6].

Adding 1 g·kg-1 mannan-oligosaccharides to the diet of meat ducks can significantly increase daily weight gain, improve feed conversion rate, significantly inhibit the reproduction and growth of Escherichia coli in the intestine, and at the same time promote the reproduction and growth of Lactobacillus, so that the intestinal flora is more conducive to the growth of meat ducks. The effect of combining mannan-oligosaccharides with antimicrobial peptides is significantly better than that of mannan-oligosaccharides alone [7]. The addition of mannan-oligosaccharides to the diet of meat ducks can also bind to the surface of certain toxins, viruses and eukaryotic cells and act as an adjuvant for these foreign antigens, which can slow down the absorption time of the antigens and increase the potency of the antigens.

When used together with duck vaccines, mannan-oligosaccharides can delay the absorption time of the vaccines and increase their effect, increasing the body's cellular and humoral immunity. Adding 0.1% mannan-oligosaccharides to the diet of Cherry Valley ducks can increase the final body weight of the ducks by 5.96%, the average daily weight gain by 6.65%, and the utilization rates of dry matter, crude ash, and crude protein increased by 9.21%, 22.09% and 10.64% respectively, the number of Lactobacillus in the cecum increased significantly, and Escherichia coli and pH decreased significantly [9].

2.3 Ruminants

Mannan-oligosaccharides have been used less frequently in ruminants, mainly because it was thought that the rumen had a strong degrading effect on oligosaccharides. At the same time, hemicellulose, cellulose, etc. can produce a large amount of oligosaccharides in the rumen, and ruminants do not need to add oligosaccharides. However, with in-depth research on the mechanism of oligosaccharides, it has been shown that oligosaccharides also have the same positive effects on the digestive tract microbiota, rumen fermentation function, immunity, nutrient digestibility and production performance of ruminants as they do on monogastric animals. 5-day Adding 4 g of mannan-oligosaccharides per head per day to the feed of 5-day-old calves can improve their growth performance, intestinal health and immunity; reduce the incidence of diarrhoea and improve feed conversion [10-11].

In the diet of early lactation dairy cows, the addition of 60 g·head-1 ·d-1 mannan-oligosaccharides can help to increase the proportion of rumen acetate fermentation and increase the milk fat rate [12]. The addition of 0.1% mannan-oligosaccharides to the diet of Mongolian sheep can improve the growth performance, serum immune function and antioxidant capacity of Mongolian sheep fed high-concentrate feed, and has a certain effect on sheep health [13]. Adding mannan-oligosaccharides to lamb diets has the effect of improving animal growth performance and immune function, improving rumen fermentation function, stabilizing and improving the rumen environment, providing favorable conditions for the growth of rumen microorganisms, promoting the proliferation of rumen microorganisms, and thereby increasing the degradation rate of crude protein and fiber in the rumen. Adding mannan-oligosaccharides to the feed can also increase the activity of proteases and fibre-degrading enzymes in the rumen, thereby increasing the degradation rate of crude protein in the rumen.

2.4 Rabbits

Adding 1 g·kg-1 mannan-oligosaccharides to rabbit feed can promote the growth of beneficial intestinal flora, especially bifidobacteria and lactobacilli, with very significant results; it can inhibit harmful intestinal bacteria, with significant inhibitory effects on Escherichia coli . Mannan-oligosaccharides have a very significant effect on the intestines. They can bind to intestinal mucosal receptors, preventing harmful bacteria and the harmful substances they produce from directly irritating the intestinal mucosa. They also have a very good protective effect on intestinal villi and the intestinal wall. They can improve feed utilization and reduce the feed-to-meat ratio. Adding mannan-oligosaccharides to rabbit feed can significantly improve the structure of the rabbit's small intestinal mucosa, enhance the immune system function of the rabbit's small intestinal mucosa, and improve the digestion and absorption function of the rabbit's small intestine, thereby promoting animal growth and improving production efficiency [14].

3 Factors affecting the efficacy of mannan-oligosaccharides

There are many factors affecting the efficacy of mannan-oligosaccharides, including the type of mannan-oligosaccharides (e.g. the monosaccharide linkage mode, purity and degree of polymerization, biological activity, etc.), addition level, addition method, animal age, animal type, interaction with other substances, etc. If the amount of mannan-oligosaccharides added is insufficient, it will not have a beneficial effect on the proliferation of beneficial bacteria. If the amount is excessive, it will increase feed costs and cause poor feed palatability, resulting in reduced feed intake and possibly diarrhea. When added together with prebiotics, mannan-oligosaccharides have a better effect than when added alone. They can prolong the action time of feed microorganisms and the number of viable microorganisms that reach the hindgut, promoting the proliferation and growth of beneficial microorganisms in the intestine [15-17].

4 Summary

The new feed additive mannan-oligosaccharide has many unique advantages over antibiotics for animals. Mannan-oligosaccharide has the effects of antibiotics in promoting growth and preventing diarrhea, but does not cause many disadvantages such as bacterial resistance, drug residues, immunosuppression, etc., as antibiotics do. It is a natural, green, and highly effective immune regulator and growth promoter.

At present, there are many reports on the application of mannan-oligosaccharides in livestock and poultry production, but some aspects of the research are not yet in-depth, such as the optimal dosage and method of adding mannan-oligosaccharides to different animals, in different physiological states, at different physiological stages, and under different production conditions, and the interaction between mannan-oligosaccharides and other nutritional and non-nutritional factors. Today, food safety and bacterial resistance are receiving attention, and both domestically and abroad there is a trend towards banning antibiotics as growth-promoting additives. In this environment, it is urgent to find new green feed additives. Mannan-oligosaccharides have the characteristics of being purely natural, safe, non-residual, structurally stable, and not easily inactivated during storage and processing. They can improve the growth performance of animals and the disease resistance of animal bodies, and have good application prospects in animal husbandry production.

References:

[1] Li Yuxin. Effects of mannan-oligosaccharides from Pichia pastoris on the production performance and immune function of pigs [D]. Beijing: China Agricultural University, 2015.

[2] Li Yuxin, Zhang Limei, Han Dandan, et al. Effects of mannan-oligosaccharides from Pichia pastoris on the production performance, intestinal villi and cytokines of weaned piglets [J]. Chinese Journal of Veterinary Medicine, 2015, 51(11): 33-35.

[3] Zhang Junxia, Li Zudong. Effect of mannan-oligosaccharides on growth performance of weaned eight-eyebrow dual-purpose piglets [J]. Feed Industry, 2015, 36(10): 41-43.

[4] Wu Wei, Zheng Yunduo, Jia Linan, et al. Effect of mannan-oligosaccharides on early growth performance and related physical and chemical indicators of broiler chickens [J]. China Poultry, 2017, 39(1): 34-37.

[5] Song Xinlei, Zhu Lianqin, Lin Gang, et al. Effects of combined application of mannan-oligosaccharides and organic selenium on the production and immune performance of broilers [J]. China Poultry, 2018, 40(8): 24-27.

[6] Wan Dan, Tang Zhenhua, Xia Zhongsheng, et al. Effects of fructooligosaccharides and mannan-oligosaccharides on the production performance, nutrient metabolism rate of feed and serum biochemical indicators of yellow-feathered broiler breeders [J]. Feed Industry, 2015, 36(2): 41-46.

[7] Zang Sumin, Song Yong, Li Tongzhou, et al. Effect of mannan-oligosaccharides on the production performance, nutrient digestibility and main cecal flora of meat ducks [J]. Journal of Animal Nutrition, 2005 (4): 55.

[8] Yu Shaohai. Research on the application of mannan-oligosaccharides and antimicrobial peptides in the production of meat ducks [D]. Yangzhou: Yangzhou University, 2006.

[9] Song Yong. Effect of mannan-oligosaccharides on the production performance, blood biochemical indicators and main contents of cecum of meat ducks [D]. Yangzhou: Yangzhou University, 2006. [2] Li Yuxin, Zhang Limei, Han Dandan, et al. Effect of mannan-oligosaccharides from Pichia pastoris on the production performance, intestinal villi and cytokines of weaned piglets [J]. Chinese Journal of Veterinary Medicine, 2015, 51(11): 33-35.

[3] Zhang Junxia, Li Zudong. Effect of mannan-oligosaccharides on growth performance of weaned eight-eyebrow dual-breed piglets [J]. Feed Industry, 2015, 36(10): 41-43.

[4] Wu Wei, Zheng Yunduo, Jia Linan, et al. Effect of mannan-oligosaccharides on early growth performance and related physical and chemical indicators of broiler chickens [J]. Chinese Poultry, 2017, 39(1): 34-37.

[ 5 ] Song Xinlei, Zhu Lianqin, Lin Gang, et al. Effect of combined application of mannan-oligosaccharides and organic selenium on broiler production performance and immune function [J]. Chinese Poultry, 2018, 40(8): 24-27.

[6] Wan Dan, Tang Zhenhua, Xia Zhongsheng, et al. Effects of fructooligosaccharides and mannan-oligosaccharides on the production performance, nutrient metabolism rate of feed and serum biochemical indicators of yellow-feathered broiler breeders [J]. Feed Industry, 2015, 36(2): 41-46.

[7] Zang Sumin, Song Yong, Li Tongzhou, et al. Effect of mannan-oligosaccharides on the production performance, nutrient digestibility and main cecal flora of meat ducks [J]. Journal of Animal Nutrition, 2005 (4): 55.

[8] Yu Shaohai. Research on the application of mannan-oligosaccharides and antimicrobial peptides in the production of meat ducks [D]. Yangzhou: Yangzhou University, 2006.