Fermented liquid feed — Feed processing has a big impact on microbial degradation of free lysine during fermentation

In order to investigate the influence of feed processing on the microbial degradation of free lysine during fermentation of liquid feed, a study at laboratory scale was carried out. Based on a standard Danish grower diet with extra free amino acids added, two treatments were prepared: treatment 1) pelleted (83 °C) diet; treatment 2) mash, non-heated diet. The feed was mixed with water (1:2.75, w/w) and incubated at ∼ 25 °C. The number of Enterobacteriaceae was higher in liquid feed prepared with the mash than with the pelleted feed immediately after feed and water were added to the mixture but after a few hours of fermentation, the levels in both treatments became similar. The concentration of acetic acid was higher in the mixture containing the mash feed than in that containing the pelleted feed. The disappearance of free lysine was much higher when mash feed was fermented than when the same pelleted feed was used. This was specially observed in a more established FLF (after backslopping had been practiced for several days). In conclusion, the data showed that free lysine was degraded to a high extent when fermenting non-pelleted–non-heated feed, whereas a limited degradation occurred during fermentation of pelleted–heated feed.