Changes in the distribution of nitrogen and plant enzymatic activity during ensilage of lucerne treated with different additives |
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| Authors: | X Guo H Zhou Z Yu Y Zhang |
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| Institution: | Grassland Science Department of Institute of Animal Science, China Agricultural University, Beijing, China |
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| Abstract: | Effects of formic acid, formaldehyde and two levels of tannic acid on changes in the distribution of nitrogen (N) and plant enzymatic activity during ensilage of lucerne (Medicago sativa) were studied. Lucerne 300 g dry matter (DM) kg?1 forage] silages were prepared untreated (control) and with formic acid (4 g kg?1 DM), formaldehyde (1 g kg?1 DM) and two levels of tannic acid (20 and 50 g kg?1 DM) as additives. Inhibition of proteolysis by formic acid was more effective than the other additives during the first 7 d of ensiling. Tannic acid was as effective at inhibiting production of non‐protein‐N, ammonia‐N and free amino acid‐N as formic acid and formaldehyde. However, increased concentrations of non‐protein‐N and free amino acid‐N in silage from day 1 to 35 of ensiling were less with the higher level of tannic acid than that in the control and other additive‐treated silages. Carboxypeptidase lost its activity slowly with increasing time of ensiling. At day 2, it still had 0·79 of the original activity in the control silage. After 21 d of ensiling, high levels of carboxypeptidase activity, proportionately 0·41, 0·49, 0·10, 0·35 and 0·30 of the original activity, remained in the control silage, and silages made with formic acid, formaldehyde, and low and high levels of tannic acid respectively. There were higher levels of activity of acid proteinase in formic acid‐treated silage than in the control silage until day 2 of ensilage indicating that the reduction of proteolysis by formic acid was probably due to acidifying the forage below the pH optima of plant protease. Aminopeptidase activity in all silages declined rapidly after ensiling. |
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| Keywords: | alfalfa silage non-protein-N carboxypeptidase aminopeptidase acid proteinase |
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