Maillard reaction products as a substrate in in vitro rumen fermentation

Maillard reaction products (MRPs) were generated by autoclaving equimolar solutions of glucose and either urea, glycine, acidic (AHC) and enzymic (EHC) hydrolysates of casein, peptone or casein. The MRPs contained small amounts of residual glucose, acetate, formate and free amino groups. Main products had molecular weights ranging from 0.4 to 22.5 kDa, contained small amounts of acetate, formate and glucose. No volatile fatty acids were produced from the MRPs incubated with rumen fluid for 8 h in vitro. The MRPs of urea (5, 20 and 40 mg ml−1), glycine (20 and 40 mg ml−1) and casein (10, 20 and 40 mg ml−1) decreased VFA production by mixed rumen microorganisms.