Effects Of Coated Essential Oil And Organic Acids On The Growth Performance And The Intestinal Microbiota Of Broilers

With the development of intensive and scale-up breeding of broilers, the environmental stress becomes increasingly aggressive, giving rise to various intestinal health problems induced by conditional pathogenic bacteria, which is one of the main constraints, without effective green feed additives, for the development of broiler industry. This study investigated the effects of coated essential oil and organic acids on the intestine morphology and microbiota, providing the basis for the application of coated essential oil and organic acids in the poultry industry so that the intestinal health can be improved by the optimization of intestinal microbiota.Exp. 1 Effects of the supplement of coated essential oil and organic acids on the growth performance of broilers This experiment determined the growth performance, parameters of immune organs, and the mortality of broilers by supplementing coated essential oil and organic acids into the diet periodically. 1050 1-day aged Cobb chickens were randomly separated into 7 groups, with 10 replicates per group and 15 chickens per replicate. The feeding experiment lasted for 42 days and the treatments were designed as follows:(i) negative control group with basal diet throughout the whole experimental period(C),(ii) positive control with antibiotics into the basal diet throughout the whole period(ANT),(iii) C + coated essential oil and organic acids throughout the whole period(EOA),(iv) C + coated essential oil and organic acids before d 21 and basal diet afterward(EO + C),(v) C + ANT before d 21 and basal diet afterward(ANT + C),(vi) C before d 21 and C+ ANT afterward(C + ANT), and(vii) C before d 21 and C + coated essential oil and organic acid afterward(C + EO). According to the results, no difference was found on the daily feed intake, daily weight gain, and feed conversion before d 21 among treatment groups; the feed conversion was decreased by ANT, EOA and EO-C from d 22 to 42(P<0.05); compared to C + EO and ANT + C, EO + C and C + ANT decreased the feed conversion from d 1 to 42(P<0.05). There was no significant effect on the parameters of immune organs and mortality of broilers by EO(P>0.05).The supplement of coated essential oil and organic acids throughout whole and early experimental period could increase the feed conversion from d 22 to d 42 and the supplement of EO before d 21 could also improve the feed conversion throughout the whole period.Exp. 2 Effects of supplement of coated essential oil and organic acids into the diet on the intestinal function of broilersIn this section, the effects of coated essential oil and organic acids on the intestinal morphology, activities of enzymes, and the SIg A in the intestinal mucosa were studied by using the methods of paraffin section and HE dying together with the ELISA kits. The experimental design was the same as that in Exp. 1. The results showed that, compared with EOA and C + EO, EO + C and C + ANT improved the duodenal villus height of the broilers on d 42(P < 0.05), and the duodenal villus height of ANC + C group was higher than that in C + EO group(P < 0.05). EOA improved the jejunal villus height and the ratio of villus height to crypt depth without any significant difference(P > 0.05).EOA and EO + C increased the activities of duodenal lipase and trypsin both on d 21 and d 42(P < 0.05). Compared with group C, the EOA and EO + C groups showed improved enzyme activities of duodenal chymotrypsin(d 21 and d 42, P < 0.05), jejunal lipase and trypsin(d 21, P < 0.05), and jejunal trypsin and chymotrypsin(d 42, p < 0.05), as well as ileal trypsin and chymotrypsin(d 21, P < 0.05). Meanwhile, the activity of ileal chymotrypsin was higher in EOA group than that in other groups(P < 0.05).The SIg A content in the mucosa of duodenum in groups of C + ANT, C + EO and ANT was higher than that in EO + C and C groups on d 42(P < 0.05). Moreover, the SIg A content was appreciably higher in groups of C + ANT and C + EO than that in ANT group(P < 0.05).The supplement of coated essential oil and organic acids in the diet throughout the whole and the early period improved the duodenal villus height and the response was periodical. Besides, the coated essential oil and organic acids could increase the activities of trypsin, lipase and chymotrypsin both in duodenum and jejunum, as well as the duodenal SIg A content with a periodical response.Exp 3. Effects of supplement of coated essential oil and organic acids on the small intestinal microbiota of broilersThis experiment explored the effects of periodical supplement of coated essential oil and organic acids on the microbiota in duodenum, jejunum and ileum of broilers by PCR-DGGE together with the biology methods, such as DNA sequencing. The experimental design was the same as that in Exp. 1. Based on the experimental results, coated essential oil and organic acids could change the structure of the intestinal microbiota, which consequently influenced the amount and proportion of different microorganisms:(i) it decreased the content of intestinal lactobacillus aviarius, lactobacillus amylovorus, and lactobacillus salivarius in duodenum;(ii) it increased the content of lactobacillus salivarius, lactobacillus reuteri, and lactobacillus amylovorus in jejunum(from d 22 to d 42);(iii) it decreased the content of the lactobacillus amalovorus and lactobacillus reuteri(from d 22 to d 42);(iv) it increased the lactobacillus amylovorus in ileum(from d 22 to d 42). The continuous response of microbiota to the supplement of coated essential oil and organic acids, reflected by the increasing number of preponderant species, lasted from d 1 to d 21. The results of component analysis of the microbiota structure showed that coated essential oil and organic acids could maintain the microbiota structure in jejunum. After the recycling of the characteristic bands and sequencing from DGGE, we found that the preponderant bacteria species was lactobacillus, which existed periodically.The supplement of coated essential oil and organic acids throughout the whole and early period into the diet decreased the content of duodenal lactobacillus amylovorus, lactobacillus salivarius, and the intestinal lactobacillus aviarius, while increased the ileal lactobacillus amylovorus. And the effects of the supplement before d 21 on the intestinal microbiota lasted to the later period.To this end, the supplement of coated essential oil and organic acids into the diet improved the suppression on the growth performance by the intestinal lactobacillus aviarius by changing the microbiota structure in duodenum, jejunum and ileum. Besides, the supplement increased the activities of intestinal enzymes and improved the structure of duodenum and jejunum by increasing the content of lactobacillus amylovorus in ileum, and finally improved the growth performance of broilers.