Antibiotic Substitute--Application of Quercetin in Livestock and Poultry

Quercetin is one of the most widely distributed natural flavonoids in nature and is widely found in various fruits, vegetables, grains and some Chinese herbal medicines. Quercetin has various biological activities such as antibacterial, anti-inflammatory, antioxidant, and anti-obesity. As a nutritional supplement and food additive, it has high research and practical application value in modern antibiotic-free livestock and poultry breeding. According to reports, quercetin has benefits in improving the production performance of livestock and poultry, improving the quality of meat and eggs, enhancing the immunity of livestock and poultry, effectively preventing and treating livestock and poultry diseases, improving the utilization rate of nutrients, and regulating the metabolism of livestock and poultry.

1. Improve the production performance of livestock and poultry, and improve the quality of meat and eggs

Research has found that adding an appropriate amount of quercetin to the diet of Haisai laying hens can significantly reduce the average feed-to-egg ratio, egg soft shell breaking rate, and eggshell phosphorus content, and significantly increase the average egg production rate, relative eggshell weight, and eggshell phosphorus content. Shell strength, eggshell thickness, and eggshell calcium content indicate that quercetin can improve the feed conversion rate and egg quality of Haisai laying hens , thereby improving economic benefits. Another study shows that adding quercetin to the diet of laying hens can also significantly increase the Hastelloy units, egg yolk phospholipid and crude protein content, and significantly reduce the egg yolk cholesterol content.

Pigs are often affected by noise, fasting, crowding and temperature changes during road transportation, which can easily cause stress and damage to the intestinal barrier function of pigs. Transport stress has profound effects on the gastrointestinal tract, and quercetin can alleviate intestinal damage caused by transport stress. Through experimental studies on the effects of adding quercetin on intestinal integrity, intestinal ROS levels and intestinal inflammation in pigs under transportation stress, it was found that quercetin has a protective effect on intestinal integrity. In particular, adding 25 mg/kg quercetin to the diet of finishing pigs can significantly increase the height of small intestinal villi and the mRNA levels of Occludin and ZO-1. Quercetin can also reduce serum LPS, ROS and malondialdehyde levels, and reduce serum TNF-α, interleukin-1 (IL-1), IL-6 and monocyte chemoattractant protein-1β levels. It shows that quercetin can improve the pork quality and disease resistance of fattening pigs.

Studies have found that adding an appropriate amount of quercetin to broiler chicken feed can improve the brightness and redness of meat and enhance the stability of meat quality, that is, reduce the rate of fat oxidation and extend the shelf life of meat. Adding quercetin to the diet can also reduce the content of oxidized cholesterol in lamb meat. In addition, it was also found that adding quercetin to lamb diet can reduce the proportion of saturated fatty acids in lamb meat and reduce lipid peroxidation in lamb meat. Research results on the effect of quercetin on livestock and poultry meat quality show that adding quercetin to livestock and poultry diets can improve the meat quality of livestock and poultry. It can inhibit lipid peroxidation in livestock and poultry meat by exerting the antioxidant capacity of quercetin, thereby enhancing the meat quality. stability and extended shelf life.

Quercetin has the ability to protect the liver and reduce lipid accumulation in the liver, which can effectively reduce the occurrence of fatty liver. Experiments have found that quercetin has a positive impact on the health of dairy cows , especially during the stress phase of early lactation, and can alleviate metabolic disorders such as fatty liver and ketoacidosis in dairy cows. Quercetin supplementation can significantly reduce the activities of plasma aminotransferase and glutamate dehydrogenase in postpartum cows, indicating that quercetin can reduce liver damage in cows.

2. Enhance the immunity of livestock and poultry, exert the regulating effect of bacterial flora, and effectively prevent and treat livestock and poultry diseases.

Livestock and poultry diseases are the main cause of death of livestock and poultry and reduced breeding efficiency. Quercetin has various biological activities such as immunity and regulating the balance of flora. It has been confirmed by many scholars that it can effectively enhance the immunity of livestock and poultry and regulate intestinal flora. , thereby reducing the occurrence of livestock and poultry diseases.

Studies have found that quercetin can significantly increase the spleen index and thymus index of AA broiler chickens, and increase serum immunoglobulin A (IgA), immunoglobulin M (IgM), complement C3, complement C4, IL-4 and TNF. - α content can also significantly increase TNF-α, TNF receptor-associated factor-2 (TRAF-2), TNF receptor superfamily member 1B (TNFRSF1B), nuclear factor kappa B p65 subunit (NF-κBp65) and The expression of gamma interferon (IFN-γ) mRNA and significantly reduced the expression of NF-κB inhibitor α (IκB-α) mRNA, suggesting that quercetin mediates the NF-κB signaling pathway triggered by TNF-α. immune response, thereby improving the immune function of broilers and enhancing disease resistance.

Quercetin can also reduce intestinal damage in pigs during transportation by regulating the expression of NF-κB signaling pathway. There is a close connection between the intestinal flora and the host in terms of energy operation and material exchange. The intestinal flora and the host can exchange substances through degradation and synthesis. The lysed cells and extracellular enzymes can be utilized by the microorganisms, while the host can also utilize the enzymes, vitamins, stimulants and cellular components of the microorganisms produced by the microorganisms. Normal microorganisms in the intestine can also directly participate in physiological and biochemical activities in the intestine, help the host degrade food, and provide the host with a variety of nutrients including vitamins, amino acids, and simple carbohydrates. In addition, the normal intestinal flora has biological antagonistic and immune effects on foreign pathogenic bacteria and conditional pathogenic bacteria, thereby greatly improving the anti-infection ability of the host mucosa. Studies have found that quercetin can reduce the number of Pseudomonas aeruginosa, Helicobacter pylori, Salmonella, Staphylococcus aureus, Escherichia coli, Clostridium perfringens and Campylobacter jejuni and increase the number of Bifidobacterium in the cecum of AA broiler chickens; The numbers of Escherichia coli, Staphylococcus aureus, Salmonella, Pseudomonas aeruginosa, Streptococcus faecalis and Enterococci in the cecum of laying hens are increased, and the numbers of Bifidobacterium and Lactobacillus are increased. It shows that quercetin can promote the growth of beneficial bacteria such as Lactobacillus and Bifidobacterium, and these intestinal beneficial bacteria can prevent the colonization of harmful bacteria through the space-occupying effect, and can also produce some active substances to inhibit harmful bacteria such as Perfringens. The growth of Clostridium, Escherichia coli, etc., thereby protecting the host from infection by harmful bacteria and invasion of foreign pathogens, and reducing the occurrence of host diseases.

3. Improve the utilization rate of nutrients and regulate the metabolism of livestock and poultry

Low protein utilization has always been a major problem faced by livestock and poultry production, and recent studies on quercetin have shown that it is expected to improve this dilemma. In a study on AA broilers, it was found that adding quercetin to the diet can promote protein deposition in broiler chickens and improve protein utilization in feed by enhancing gastrointestinal enzyme activity and activating the target of rapamycin signal transduction pathway. Quercetin can also promote protein utilization by porcine intestinal epithelial cells by regulating the expression of amino acid transport carriers, small peptide transport carriers and mammalian target of rapamycin signaling pathways. In addition, quercetin can also regulate the metabolism of livestock and poultry and reduce blood sugar and blood lipids. Research has found that quercetin can improve lipid metabolism by reducing blood lipid content in AA broilers, increasing the secretion of leptin and adiponectin, activating the PI3K/PKB signaling pathway, and ultimately reducing abdominal fat deposition in broiler chickens. Quercetin can also reduce the content of triacylglycerol in broiler hepatocytes by promoting lipid decomposition regulated by the peroxisome proliferator-activated receptor α (PPARα) signaling pathway, thereby reducing lipid deposition in broiler chickens.

Studies have found that quercetin can reduce the levels of malondialdehyde and nitric oxide by improving antioxidant enzyme activity, activating the expression of genes related to the PI3K/PKB signaling pathway that regulates glucose metabolism and reducing oxidative damage, and alleviates streptozotocin-induced Oxidative stress side effects, thereby reducing fasting blood glucose and fasting insulin levels, indicate that quercetin has an inhibitory effect on streptozotocin-induced hyperglycemia in AA broilers, and its mechanism of action may be achieved by reducing oxidative stress. Studies have shown that adding quercetin to the diet has no significant effect on the blood lipids of laying hens during peak egg production, but can significantly increase the levels of very low-density lipoprotein cholesterol, apolipoprotein B, and apolipoprotein A in the serum of laying hens. , thereby increasing the total phospholipid and lecithin content in egg yolk. Studies have shown that quercetin can promote the efflux of cholesterol from the body by promoting the conversion of cholesterol into bile acids.

Against the backdrop of the current ban on antibiotics, quercetin, as a new green additive, has broad application prospects in livestock and poultry production. However, in the actual application process, quercetin still has many limitations. For example, the preparation process is not yet mature, the price is still relatively expensive compared with antibiotics, and it cannot be fully introduced to the market. The biological activity has been studied thoroughly, but the mechanism of action still needs to be Further in-depth research; the dosage of additives in feed needs to be discussed. Therefore, in order to speed up the advancement of quercetin as an alternative to antibiotics, many scientific researchers still need to continue to strengthen relevant research on quercetin so that it can enter the market as soon as possible.