| Lipids are one of the essential nutrients for the maintenance of normal life activities.According to the different chain length,fatty acids can be divided into long,medium and short chain fatty acids.Among them,short chain and medium chain fatty acids and their glycerides can be absorbed by the body independent of bile salts and pancreatic lipase,and have the functions of promoting intestinal growth and development and inhibiting the activity of pathogenic bacteria.Growing pigs are in the period of rapid growth.However,due to the influence of weaning period,adverse weaning reactions tend to prolong the fattening and marketing time of growing pigs.However,the traditional methods of adding antibiotic growth promoters have many disadvantages,such as bacterial resistance,disruption of the balance of normal intestinal flora and antibiotic residues.Therefore,it is urgent to find a feed additive that can replace antibiotic growth promoters and improve digestive tract environment in breeding,but the effect of a single medium chain or short chain glycerides is not ideal.While there are few reports about the effects of combination or inclusion of medium chain and short chain glycerides on growing pigs.Therefore,the purpose of this experiment is to add coated medium chain and short chain glycerides,uncoated medium chain and short chain glycerides,glycerol monolaurate and chlortetracycline to the diet,to analyze their effects on the growth performance,intestinal morphology and microbiota of growing piglets.And provide ideas for the replacement of antibiotics.1 Effects of dietary supplementation of short and medium chain fatty acid glycerides on growth performance,liver and serum biochemical indexes of growing pigsA total of 240 weaned piglets with similar body weight were randomly divided into 5 groups:control group(CON),medium and short chain glycerides uncoated group(UG),medium and short chain glycerides coated group(CG),glycerol monolaurate(GML)and chlortetracycline(CHL).The main components of UG and CG are medium chain glyceride and tributyrin.The difference is that CG is processed by coating process.Except for the CHL,antibiotics were not added in other groups.For each group of 48 pigs,there were 3 replicates,16 piglets per replicate,half male and half female.The trial period was 29 days.The initial and final weights and feed intake per pen were recorded.At the end of the experiment,blood samples were collected and organs were weighed.The results showed that,compared with the CON,the average daily weight gain and total weight gain of growing pigs were significantly increased by adding medium chain and short chain glycerides to the diet(P<0.05).Compared with the CON,both the CG and the UG significantly increased the liver weight(P<0.05),while there was no significant difference in the ratio of liver weight to body weight.Compared with the control group,the total serum protein level of the growing pigs was reduced in CHL(P<0.05),while GML tended to increase its level(0.05<P<0.7).The content of free fatty acids in serum of the CG and GML decreased significantly compared with the control group(P<0.05).The content of cholesterol and triglyceride in the liver was found to be significantly reduced in the CG(P<0.05).Compared with the control group,the contents of serum T3,T4 and insulin in the CG were significantly increased(P<0.05),and the serum cortisol levels in the CG and UG were significantly decreased(P<0.05).2 Effects of dietary supplementation of short and medium chain fatty acid glycerides on intestinal mucosal structure,expression of fatty acid receptors and transportation-related factors in growing pigsThe experimental design and grouping were the same as above.The tissue and molecular samples of duodenum and colon were collected.The results showed that compared with the control group,the duodenal villi height and crypt depth were significantly increased in the CG and the GML(P<0.05).However,compared with the control group,the villi height and the velvet hidden ratio were significantly reduced in the CHL(P<0.05).Compared with the control group,the colonic pH of the UG was significantly reduced(P<0.05).Compared with the control group,the expression level of long-chain fatty acid receptor GPR120 was significantly increased in the four experimental groups(P<0.05).The expression level of short-chain fatty acid receptor GPR43 was significantly increased in the UG and GML(P<0.05).Only the CG significantly increased the expression level of medium-chain fatty acid receptor GPR84(P<0.05).Compared with the control group,the protein expression levels of CD36,FATP1 and FATP4 were significantly increased in the four experimental groups(P<0.05).Compared with the control group,only GML significantly increased the expression level of duodenal fatty acid transporter CD36(P<0.05).3 Effects of dietary supplementation of short and medium chain fatty acid glycerides on gut microbiota of growing pigsThe experimental design and grouping are the same as above.Colonic chyme was collected and 16S rDNA high-throughput sequencing was performed on the colonic flora.Of the total 2367 OTUs,765 OTUs(approximately 32%)co-existed in the control and experimental groups.Compared with the control group,the Alpha Diversity index of the coated group was lower than that of the control group(P<0.05),but there was no significant difference between the uncoated group and the monolingual laurate group and the control group.Compared with the control group,the abundance of Staphylococcus,Methanobrevibacter and Bacillus in UG,CG and GML decreased.The abundance of Lactobacillus increased significantly in both the UG and the CG.In addition,UG,CG and GML also increased the abundance of bacteria with the ability of producing volatile fatty acids,such as Roseburia,Blautia and Faecalibacterium.The above results showed that the combination of medium chain and short chain glycerides can promote growth and intestinal development better than the single glycerol monolaurate,and increase the bacteria with the ability to produce volatile fatty acids in the intestinal tract. |
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