Changes in the distribution of nitrogen and plant enzymatic activity during ensilage of lucerne treated with different additives

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 nonprotein-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 0AE79 of the original activity in the control silage. After 21 d of ensiling, high levels of carboxypeptidase activity, proportionately 0AE41, 0AE49, 0AE10, 0AE35 and 0AE30 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.

Effects of condensed tannins in wrapped silage bales of sainfoin (Onobrychis viciifolia) on in vivo and in situ digestion in sheep

“…The NH 3 -N and soluble N levels (expressed in %N) reported by Dentinho et al (2006) on sulla (Hedrysarum coronarium L) silages were lower than those in our study for soluble N), despite similar N concentrations. However, Cavallarin et al (2005) found high NH 3 levels (.12%N) in sainfoin silages, possibly because of clostridial activity and enterobacteria, although tannins are known to reduce the activities of silage bacteria and moulds (Guo et al, 2007). Albrecht and Muck (1991) found that the level of non-protein N in different legume silages was negatively correlated to tannin concentration, and especially sainfoin silage showed almost constant values ranging from 350 to 430 g/kg N, in agreement with our results.…”

Contribution of exopeptidases to formation of nonprotein nitrogen during ensiling of alfalfa

“…Therefore, aminopeptidase and dipeptidyl-peptidase played a small role in the formation of NPN during proteolysis, which agrees with the previous findings (McKersie, 1981;Guo et al, 2007). In addition, reductions in NPN relative to control of 27 and 21% of by PCI and butabindide on d 21 indicated that the carboxypeptidases and tripeptidyl-peptidase also played a role in the formation of NPN.…”

“…In addition, reductions in NPN relative to control of 27 and 21% of by PCI and butabindide on d 21 indicated that the carboxypeptidases and tripeptidyl-peptidase also played a role in the formation of NPN. Previous studies suggested that the carboxypeptidase and acid proteinase might be the principal enzymes that hydrolyze proteins of ensiled forage, because both enzymes were comparatively stable during the ensiling period and were still active after 21 d of ensiling (McKersie and Buchanan-Smith, 1982;Guo et al, 2007). Results of the current study further confirmed that dipeptidase, carboxypeptidase, and tripeptidyl-peptidase were the main enzymes that hydrolyze the proteins of the ensiled forage.…”

“…Previous studies suggested that carboxypeptidase and acid proteinase might be the principal enzymes hydrolyzing the proteins of ensiled alfalfa forage (McKersie and Buchanan-Smith, 1982;Guo et al, 2007). Studies characterizing exopeptidases in other plants have been well documented (Sopanen, 1976;Davy et al, 2000;Yang et al, 2004;Book et al, 2005;Kumada et al, 2007), whereas few studies have been conducted to characterize these exopeptidases in alfalfa.…”

The effect of bale density and addition of formic acid on the <i>in situ</i> dry matter and crude protein degradation of lucerne, red clover and red fescue silages

“…The effective degradation of DM and CP of red fescue silage was not affected by the experimental factors. Guo et al (2007), who investigated changes in the activity levels of plant proteases during ensilage of lucerne treated with different additives, point to the important role played by proteolytic enzymes such as carboxypeptidase, aminopeptidase and acid proteinase; these enzymes differ with respect to pH and temperature optima and in their sensitivity to inhibitors.…”