Comparison of nitrogen transformation dynamics in non-irradiated and irradiated alfalfa and red clover during ensiling

Objective: To study the contribution of plant enzyme and microbial activities on protein degradation in silage, this study evaluated the nitrogen transformation dynamics during ensiling of non­ and irradiated alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.).

Methods: Alfalfa and red clover silages were prepared and equally divided into two groups. One group was exposed to γ­irradiation at a recommended dosage (25 Gky). Therefore, four types of silages were produced: i) non­irradiated alfalfa silage; ii) irradiated alfalfa silage; iii) non­irradiated red clover silage; and iv) irradiated red clover silage. These silages were opened for fermentation quality and nitrogen components analyses after 1, 4, 8, and 30 days, respectively.

Results: The γ­irradiation successfully suppressed microbial activity, indicated by high pH and no apparent increases in fermentation end products in irradiated silages. All nitrogen components, except for peptide­N, increased throughout the ensiling process. Proteolysis less occurred in red clover silages compared with alfalfa silages, indicated by smaller (p<0.05) increment in peptide­N and free amino acid N (FAA­N) during early stage of ensiling. The γ­irradiation treatment increased (p<0.05) peptide­N and FAA­N in alfalfa silage at day 1, whereas not in red clover silage; these two nitrogen components were higher (p<0.05) between day 4 and day 30 in non­irradiated silages than the irradiated silages. The ammonia nitrogen and non­protein nitrogen were highest in non­irradiated alfalfa silage and lowest in irradiated red clover silage after ensiling.

Conclusion: The result of this study indicate that red clover and alfalfa are two forages varying in their nitrogen transformation patterns, especially during early stages of ensiling. Microbial activity plays a certain role in the proteolysis and seems little affected by the presence of polyphenol oxidase in red clover compared with alfalfa.

Keywords: Alfalfa; Ensiling; Irradiation; Nitrogen Transformation; Red Clover

Download tại đây

Comparison of nitrogen transformation dynamics in non-irradiated and irradiated alfalfa and red clover during ensiling