Three important components of intestinal ecology and their interaction schematic diagram

These three parts play a decisive role in animal health and growth during animal production.

The interaction among the three parts (feed, microbiota and mucosa) is marked in the figure, and the main influencing factors among each component are given.

The effect of organic acids on intestinal tract is mainly bacteriostasis and metabolism regulation.

Effects of organic acids on intestinal Flora

(1) Organic acids can inhibit the growth of ph-sensitive microorganisms (such as enterobacteriaceae), but have no effect on beneficial bacteria such as lactobacillus. Organic acids can control the bacterial flora imbalance caused by weaning stress (characterized by excessive growth of Escherichia coli and inhibition of lactobacillus).

(2) The effects of acidifying agents on the digestive tract flora of weaned piglets were also different depending on the types, doses and analysis of intestinal segments.

(3) The dosage of formic acid (salt) ≥0.6% can effectively reduce the number of E. coli in the gastrointestinal tract, which has a more obvious influence on the changes of microbial flora in the small intestine than the lower intestinal segment.

(4) Organic acids mainly play a role in the proximal end of the stomach and small intestine. After passing the stomach, the undissociated organic acid molecules are insufficient, which inhibits the antibacterial effect of organic acids. After adding organic acids to the diet, high concentrations are maintained only in the proximal end of the stomach and small intestine, and they disappear in the distal end of the small intestine and the contents of the large intestine.

(5) Supplementation of MCFA (0.3% octanoic C8 or 0.3% decanoic C10) reduced the number of E. coli in jejunum and cecum of weaned piglets.

(6) The results were different when the mixture of organic acid and MCFA was added to the diet.Some results showed that the colonic microbe diversity could be increased and the colonic microbe diversity could be decreased.Other studies have shown that simultaneous addition does not affect the microflora of the large intestine or faeces.

Organic acids on intestinal fermentation function adjustment

(1) Formic acid is the most studied. In some cases, the addition of 3%-3% formic acid does not change ammonia and VFA production in the gastrointestinal tract.In other studies, formic acid (salt) can increase the concentration of acetic acid in ileum, cecum and colon, and reduce the concentration of lactic acid.This indicates a change in the composition of the host intestinal flora, with microbial fermentation regulating more nutrients (such as glucose that has not been fermented into lactic acid) or metabolites (such as acetate) for use by the host.

(2) The jejunal crypt depth of broiler chickens fed a diet containing formic acid (1%) was deeper than that of the antibiotic group (266 Vs 186 um).Therefore, the addition of formic acid can increase both intestinal villi height and crypt depth.Short-chain fatty acids have been shown to stimulate the proliferation of normal crypt cells and promote turnover and maintenance of healthy tissues.

(3) Organic acids can regulate the microbial flora of the gastrointestinal tract, and then regulate the production of microbial metabolites.

(4) Different organic acids (pure acids or salts, alone or in different combinations) and other factors (such as the gut) may produce different metabolites, especially VFA.

(5) Sometimes, organic acids are often ineffective even at high doses, possibly due to the ability of organic acids to dissociate in the gastrointestinal tract.