Characterization of nitrogen transformation dynamics in alfalfa and red clover and their mixture silages

The objective of this experiment was to characterize the dynamics of nitrogen (N) transformations in alfalfa and red clover and their mixture during ensiling. Alfalfa, red clover and a mixture of them (1:1 on fresh weight) were ensiled for 3, 5, 7, 14 and 30 days. The fermentation qualities and dynamic change of N components of the three silages were determined. Red clover and mixed silages showed better fermentation qualities, indicated by lower (p < 0.05) pH value, higher (p < 0.05) lactic acid concentration compared with alfalfa silage after ensiling. Retarded N transformation was observed in red clover and mixed silages, as evidenced by lower (p < 0.05) free amino acid concentrations at all intervals of ensiling, higher (p < 0.05) peptide N and lower (p < 0.05) ammonia N concentrations after 14 days of ensiling as opposed to alfalfa silage. Mixing red clover apparently delayed the degradation process of alfalfa protein in mixed silage, as demonstrated by no significant difference in non-protein N (NPN) concentrations in comparison with pure red clover silage at most intervals of ensiling. The results of this study, from the perspective of N transformation, confirmed the lower rate of protein degradation in red clover in contrast to alfalfa during ensiling and potentially provide an effective strategy to reduce protein loss for alfalfa silage production.