In vitro total-gas, CH4, H2, volatile fatty acid, and lactate kinetics studies on luminal contents from the small intestine, cecum, and colon of the pig
1989
Robinson, J.A. | Smolenski, W.J. | Ogilvie, M.L. | Peters, J.P.
Two experiments were conducted to assess differences in fermentative activities of digesta obtained from various regions of the pig gastrointestinal tract. In experiment 1, the contents of small intestines, ceca, and colons of 110-kg pigs were collected, diluted twofold, and incubated for 2 h at 37 degrees C. In experiment 2, colonic samples from 16 100-kg pigs were similarly treated, except that the incubation period was 5 h. Total gas (gas pressure), CH4, H2, lactate, formate, acetate, propionate, butyrate, valerate, and isovalerate were measured in experiment 1. Only the gas variables were measured in experiment 2. Statistically significant differences (P greater than 0.05) were not observed among the gas production rate estimates across the small-intestinal, cecal, and colonic regions in experiment 1. Furthermore, all the small-intestinal samples and half the cecal samples assayed in experiment 1 were nomethanogenic. The mean methanogenic and total-gas production rate estimates for the colonic samples in experiment 1 were 0.052 ml g of wet contents-1 h-1 and 1.7 ml of total gas g of wet contents-1 h-1, respectively. No differences in the methanogenic rate estimates were detected between the proximal, middle, and distal thirds of the pig colons (P greater than 0.05). The volatile fatty acid and lactate molar percentages measured in experiment 1 were consistent with previously published observations. Hydrogen accumulated to the greatest extent (7 microM on average) in the in vitro incubations of small-intestinal contents, whereas the H2 concentrations ranged from 0.5 to 1 microM for the incubated cecal and colonic samples in experiment 1. In experiment 2, the variability of the cumulative gas production rate estimates was lower (coefficient of variation, 24%) than that observed for the CH4 production rates (coefficient of variation, 58%). Average rates for total gas production and methanogenesis in experiment 2 were 0.4 ml and 0.052 ml g of wet contents -1 h-1, respectively. There was a highly significant (P = 0.0003) inverse correlation (r = -0.8) between the average micromolar H2 concentration and the rate of methanogenesis, suggesting that H2 is an important methanogenic precursor in porcine colonic samples incubated in vitro.
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