Disappearance of Maillard reaction products during ensilage and rumen fermentation in vitro

The disappearance of Maillard reaction products (MRPs) during ensilage and rumen fermentation was studied. MRPs were prepared by heating mixtures of D -glucose and glycine (GG) or D-xylose and glycine (XG); lyophilised powder (MW > 1000) was subjected to anaerobic incubation for 24h with lucerne juic e or buffered rumen fluid. Changes in MRPs were assessed by comparing gel f iltration profiles before and after incubation, and the proportion of disap peared MRPs was calculated based on the area under the curve. A portion of MRPs, particularly high-MW fractions, disappeared when incubated with lucer ne juice, and the extent was greater (P < 0.01) in XG than in GG. The disap pearance of GG was increased (P < 0.01) when ensilage was fortified with ad ded glucose, while that of XG was unaffected with or without the fermentabl e substrate. Rumen fermentation had little impact on GG and XG, whereas a p ortion of MRPs disappeared when microbial activity was enhanced by adding l ucerne hay to the media. Volatile fatty acid production was unaffected by M RPs in either ensilage or rumen fermentation. These results suggest that th e effect on MRPs of anaerobic fermentation may be different between ensilag e and rumen digestion. Significant amounts of MRPs would enter the intestin e when ruminants are fed hay-based diets rather than silage-based diets. (C ) 2000 Society of Chemical Industry.