Effects of different organic acids on anaerobically cultured intestinal microflora in weaned piglets

Objective A research model of piglet intestinal microbial flora regulation was established in vitro. The effect of organic acids on intestinal microflora of piglets was studied.

Method In this study, for each experiment, two 40-day-old Duroc× (Landrace×large) weaned piglets were slaughtered, and the mixed chyme of jejunum and ileum was aliquoted as 300 μL every tube to 2 mL centrifuge tube, then anaerobically cultured without or with 30 mmol·L^-1 organic acid (including formic acid, acetic acid, propionic acid, butyric acid, lactic acid, fumaric acid, citric acid, benzoic acid, malic acid and sorbic acid, respectively). Genome DNA in chyme was extracted after 4 h anaerobic culture, and the numbers of the genus Lactobacillus, Bifidobacterium, Salmonella and Escherichia coli in the chyme were detected using the method of absolute quantitative PCR. Then five organic acids (formic acid, acetic acid, butyric acid, lactic acid and citric acid) which had a stronger antibacterial activity were selected for further study of its concentration gradient effects on antibacterial activities.

Result and conclusion The total chyme anaerobic culture system was successfully established in vitro. As a result, formic acid, butyric acid, and citric acid present dose dependently inhibited the proliferation of bacteria, but acetic acid had no obvious effects on the number of total bacteria. As for probiotics, citric acid could significantly inhibit the proliferation of Lactobacillus and Bifidobacterium. However, the low dose of lactic acid (10 mmol·L^-1) could significantly promote the proliferation of Lactobacillus and Bifidobacterium, and the low dose of acetic acid (15 mmol·L^-1) could also promote Bifidobacterium proliferation. At the concentration levels of 10-15 mmol·L^-1, all of the organic acids tested in this study effectively inhibited the proliferation of pathogenic bacteria (Salmonella and E. coli). The results of this study provide a simple and effective model for optimizing the species and optimal dose of acidifier used in pig production, and when microflora is regulated with single organic acid under the anaerobic condition, 15 mmol·L^-1 acetic acid and 10-15 mmol·L^-1 lactic acids are good choices.