In this experiment, the in vitro gas test revealed the course of fermentation of selected carbohydrates, namely glucose, fructose, sucrose, inulin, inulin from Sigma, beta glucan, molasses and commercial product Molkolac instant containing 83 % of lactose. In addition to determining gas production of selected substrates, the concentration of volatile fatty acids after 8 hours of incubation in the inoculum prepared from the caecal content of the rabbit was also determined. Gas production kinetics parameters were estimated with the Gompertz model, and the maximum fermentation rate (MFR), the time of maximum fermentation rate (TMFR), the lag phase (LAG), the amount of gas generated within 8 hours (GAS8), the maximum fermentation rate within 8 hours (MFR8), the total amount of SCFA, the proportions of individual SCFAs, and the relationship between individual SCFAs. Total gas production was the highest in fermentation of sucrose (385,8 ml/g SS) and the smallest in molasses (196,1 ml/g SS). The shortest LAG belonged to molasses (2,05 h) and the longest to inulin from Sigma (7,35 h). The highest rate of fermentation within 8 hours, as well as in the whole study, are belonging to glucose, fructose, sucrose and inulin. Furthermore, the 4 mentioned substrates formed the highest amounts of SCFAs. The largest proportion of SCFA belonged to acetic, then butyric and finally propionic acid. The ratio between acetic and propionic was wider than that between propionic and butyric acid.
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