Effect of gluconic acid on piglet growth performance, intestinal microflora, and intestinal wall morphology.

Gluconic acid (GA) derives from the incomplete oxidation of glucose by some Gluconobacter strains. When fed to monogastric animals, GA is only poorly absorbed in the small intestine and it is primarly fermented to butyric acid in the lower gut. This study investigated the effect of GA on in vitro growth response and metabolism of swine cecal microflora and on animal growth performance, intestinal wall morphology and intestinal microflora. During a 24-h in vitro cecal fermentation, total gas production and maximum rate of gas production were increased by GA (linear, P < 0.001). Ammonia in cecal liquor was reduced by GA after 4 h, 8 h and 24 h of fermentation (quadratic, P < 0.01). After 24 h of fermentation, total short-chain fatty acids(SCFA), acetic acid, propionic acid, n-butyric acid, acetic to propionic acid ratio, and acetic + butyric to propionic acid ratio were linearly increased by GA (P < 0.001). In the vivo study, 48 piglets were divided into four groups and housed in individual cages for six weeks. Piglets received a basal diet with a) no addition (control) or with GA at b) 3,000 ppm, c) 6,000 ppm, and d) 12,000 ppm. After six weeks, four animals per treatment were killed and samples of intestinal content and mucosa were collected. Compared with control, GA tended to increase average daily gain ( +13% and +14% for GA at 3,000 and 6,000 ppm, respectively; P of the model = 0.11; quadratic, P < 0.05). Daily feed consumption and gain to feed ratio were not influenced by GA. Intestinal counts of clostridia, enterobacteriaceae, and lactic acid bacteria were not affected by feeding GA. Gluconic acid tended to increase total SCFA in the jejunum (+174%, +87%, and +74% for GA at 3,000, 6,000, and 12,000 ppm, respectively; P of the model = 0.07; quadratic, P = 0.07).The morphological evaluations of the intestinal mucosa samples from jejunum, ileum and cecum did not show any significant differences among treatments. This study showed that feeding GA has an influence on the composition and the activity of the intestinal microflora and may improve the growth performance of piglets after weaning.