| With the complete prohibition of antibiotics and antibiotic substances as feed additives in the animal husbandry industry in China,the intestinal health regulation function of antibiotics has appeared in a vacuum,and the intestinal health of poultry is facing new challenges.Therefore,various additives with the potential to replace antibiotics have become a research hotspot in the field of animal nutrition.Medium-chain fatty acids are compounds mainly derived from plants.They have special structural properties and can regulate the intestinal health of poultry.They have been gradually applied in aquaculture production.This experiment firstly explored the effects of medium-chain fatty acids on the performance and intestinal development of broilers during normal feeding,and determined the growth-promoting effect of medium-chain fatty acids on broilers;The effects of production performance,blood immune indexes,and intestinal barrier function are aimed at evaluating its effectiveness and safety as a feed additive,and providing technical support and theoretical basis for the application of medium-chain fatty acids in broiler production.Trial Ⅰ was designed to investigate the effect of medium-chain fatty acids on performance and intestinal development in broilers under normal growth conditions.A total of 192 1-day-old healthy male AA broilers were selected and randomly divided into two treatment groups（control group and medium-chain fatty acid group）,with 8 replicates in each treatment group and 12 chickens in each replicate.The control group was fed the basal diet,and the medium-chain fatty acid group was supplemented with 700 mg/kg of medium-chain fatty acids in the basal diet,and other feeding conditions were the same.The experimental period was 42 days and was divided into early stage（1-21 days old）and late stage（22-42 days old）.On the 21st and 42nd,the organs were weighed,blood,gut,and terminal ileal chyme were collected,and the organ index,carcass composition,and intestinal enzyme activities,intestinal morphology,and microbial composition and diversity of the terminal ileal chyme were determined.The results showed that medium-chain fatty acids could significantly increase the body weight（BW）of broilers at 21 and 42 days of age,significantly reduce the feed to meat ratio（FCR）at each stage,and significantly increase the average daily feed intake（ADFI）of 1-42-day-old broilers（P<0.05）.Medium-chain fatty acids can significantly improve the glandular stomach index of broilers at 21 days of age（P<0.05）,improve the glandular stomach index at 42 days of age（P<0.10）,and significantly increase the V/C of the duodenum and jejunum of broilers at 42 days of age.value and duodenal trypsin activity（P<0.05）.In addition,medium-chain fatty acids had no significant effect on microbial diversity in the terminal ileum of broilers（P>0.10）,but medium-chain fatty acids significantly increased the abundance of Lactobacillus in the terminal ileum of 21-and 42-day-old broilers（P<0.05）.It can be seen that adding 700 mg/kg of medium-chain fatty acids to the broiler diet can improve the glandular stomach index,improve the intestinal morphology,increase the duodenal trypsin activity and the relative abundance of Lactobacillus in the terminal ileum,thereby improving the meat quality.chick performance.Trial two was designed to explore the effects of medium-chain fatty acids on the production performance and intestinal immune barrier function of broilers under E.coli challenge.312 1-day-old healthy male AA broilers were selected and randomly divided into 3groups（blank control group,blank challenge group,and medium-chain fatty acid challenge group）.Eight replicates per treatment group with 13 birds per replicate.The blank control group and blank challenge group were fed a basal diet,and the medium-chain fatty acid challenge group was supplemented with 700 mg/kg of medium-chain fatty acids in the basal diet.At 7and 11 days of age,each broiler in the blank control group was orally administrated 1 mL of PBS buffer solution,and each broiler in the blank challenge group and medium-chain fatty acid challenge group was administrated 1 mL of Escherichia coli bacteria solution（2×10~8 CFU/mL）.The test period was 42 days.The production performance was counted at 14,18,21,and 42days of age.Blood,terminal ileal chyme,duodenum,jejunum,ileal intestinal segment,and jejunal mucosa were collected for corresponding index detection.The test results showed that E.coli challenge led to a significant decrease in BW at 18 days of age and a significant increase in FCR at 1-18 days of age in the blank challenge group（P<0.05）.The growth inhibition and feed-to-meat ratio increased,and the body weight of the broilers was maintained basically the same as that of the blank control group.Compared with the blank challenge group,the medium-chain fatty acid challenge group significantly increased the 21-day-old spleen index,duodenal index and jejunum index（P<0.05）,and significantly increased the 14-day-old serum lysozyme（P<0.05）.content and 18-day-old immunoglobulin（Ig）A,Ig M content（P<0.05）,18-day-old diamine oxidase（DAO）content was significantly decreased（P<0.05）,and the medium-chain fatty acid challenge group significantly decreased Increased jejunal villus height in 18-day-old broilers（P<0.05）.Additionally,although there was no significant difference in microbial diversity in the terminal ileum at 21 and 42 days of age（P>0.05）,medium-chain fatty acids significantly increased the abundance of Lactobacillus at 21 and 42 days of age（P<0.05）.E.coli challenge significantly increased the mRNA expressions of inflammatory factors such as TLR4,TNF-α,NF-κB and IL-6 in the jejunum mucosa of broilers（P<0.05）.Medium-chain fatty acids could reduce the 14-day-old E.coli challenge.The mRNA expression of Toll-like receptor 4（TLR4）and 18-day-old interleukin（IL）-6,IL-1βand other genes in broilers（P<0.05）attenuated the intensity of inflammatory response.It can be seen that E.coli reduced the production performance of broilers and increased the mRNA expression of inflammatory factors in the jejunum mucosa.Adding 700 mg/kg of medium-chain fatty acids to the diet could improve the growth inhibition caused by E.The contents of Ig M and other immunoglobulins can reduce the mRNA expression of TLR4,IL-1βand IL-6 inflammatory factors in the jejunal mucosa,and improve the intestinal immune barrier function of broilers.In conclusion,the addition of 700 mg/kg of medium-chain fatty acids to the diet can improve the digestive organ index and intestinal morphology of broilers,increase the duodenal trypsin activity and the abundance of Lactobacillus in the terminal ileum.Growth and development of broilers;in the state of E.coli challenge,medium-chain fatty acids can alleviate the intestinal barrier damage of broilers by increasing serum immunoglobulin content and reducing the expression of inflammatory genes in jejunal mucosa.Medium-chain fatty acids can be used as an effective growth promoting feed additive in broiler industry. |
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