Gluconic acid (GA) derives from the incomplete oxidation of glucose by some <i>Gluconobacter</i> strains. When fed to monogastric animals, GA is poorly absorbed in the small intestine and can reach the lower gut where it is fermented to butyric acid. This study investigated the effect of GA on <i>in vitro</i> growth response and proteolytic state of swine caecal microflora. A diet for pigs (CP 15.8%, DE 15.0 MJ/kg) was predigested <i>in vitro</i> to simulate ileal digestion and later used as the substrate in the <i>in vitro</i> fermentation. Caecal content was collected from 6 pigs, diluted with buffer and used as inoculum. The inoculum was flushed with CO_{2}_ and dispensed into five glass syringes and five vessels per treatment, containing predigested diet. Syringes and vessels were incubated at 39°C for 24 h. There were 6 treatments: control diet, or control diet with GA added at 2,000, 4,000, 6,000, 8,000, and 10,000 ppm. Gas production was measured recording the cumulative volume of gas produced every 30 min. Samples of fermentation fluid were collected from each vessel at time 0, 4, 8 and 24 h for ammonia and at time 24 h for short-chain fatty acids (SCFA) determination. During the 24 h in vitro caecal fermentation, total gas production and maximum rate of gas production were increased by all GA concentrations in a dose-dependent manner (<i>P</i> < 0.001). Ammonia in fermentation liquor was reduced by GA at 2,000 (–26%; <i>P</i> < 0.01) and 4,000 ppm (–17%; <i>P</i> < 0.05) after 4 h and at all concentrations (<i>P</i> < 0.001) after 8 h and 24 h, with the only exception of GA at 2,000 ppm. After 24 h of fermentation, total SCFA, acetic acid, butyric acid, acetic to propionic acid ratio, and acetic + butyric to propionic acid ratio were linearly increased in all GA treatments (<i>P</i> < 0.001).This study showed that GA can positively influence the activity of the swine caecal microflora controlling the proteolysis during the 24 h of fermentation moreover implementing the production of butyric acid which maintains the mucosal health status
EFFECT OF GLUCONIC ACID ON SWINE IN VITRO CECAL FERMENTATION
PIVA, ANDREA;GRILLI, ESTER;CASADEI, GABRIELE;BIAGI, GIACOMO
2005
Abstract
Gluconic acid (GA) derives from the incomplete oxidation of glucose by some Gluconobacter strains. When fed to monogastric animals, GA is poorly absorbed in the small intestine and can reach the lower gut where it is fermented to butyric acid. This study investigated the effect of GA on in vitro growth response and proteolytic state of swine caecal microflora. A diet for pigs (CP 15.8%, DE 15.0 MJ/kg) was predigested in vitro to simulate ileal digestion and later used as the substrate in the in vitro fermentation. Caecal content was collected from 6 pigs, diluted with buffer and used as inoculum. The inoculum was flushed with CO_{2}_ and dispensed into five glass syringes and five vessels per treatment, containing predigested diet. Syringes and vessels were incubated at 39°C for 24 h. There were 6 treatments: control diet, or control diet with GA added at 2,000, 4,000, 6,000, 8,000, and 10,000 ppm. Gas production was measured recording the cumulative volume of gas produced every 30 min. Samples of fermentation fluid were collected from each vessel at time 0, 4, 8 and 24 h for ammonia and at time 24 h for short-chain fatty acids (SCFA) determination. During the 24 h in vitro caecal fermentation, total gas production and maximum rate of gas production were increased by all GA concentrations in a dose-dependent manner (P < 0.001). Ammonia in fermentation liquor was reduced by GA at 2,000 (–26%; P < 0.01) and 4,000 ppm (–17%; P < 0.05) after 4 h and at all concentrations (P < 0.001) after 8 h and 24 h, with the only exception of GA at 2,000 ppm. After 24 h of fermentation, total SCFA, acetic acid, butyric acid, acetic to propionic acid ratio, and acetic + butyric to propionic acid ratio were linearly increased in all GA treatments (P < 0.001).This study showed that GA can positively influence the activity of the swine caecal microflora controlling the proteolysis during the 24 h of fermentation moreover implementing the production of butyric acid which maintains the mucosal health statusI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
