Microbial populations, fermentative profile and chemical composition of signalgrass silages at different regrowth ages

E.M Santos,T.C Silva,R Garcia,J.S Oliveira,O.G Pereira,L.O Rosa,C.L.L.F Ferreira

doi:10.1590/s1516-35982011000400007

E.M Santos, T.C Silva + Show 5 more

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https://doi.org/10.1590/s1516-35982011000400007

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Abstract

Microbial populations, pH, ammonium nitrogen/total nitrogen (N-NH3) ratio, concentrations of lactic acid, acetic acid and butyric acid and the chemical composition of Brachiaria decumbens cv. Basiliski silages at different regrowth ages (30, 40, 50, 60 and 70 days) were evaluated by using 2-kg capacity laboratory silos. It was used a 5 × 6 factorial scheme (5 regrowth ages × 6 fermentation periods) in a complete random design, with three replicates. The fermentation periods were 1, 3, 7, 14, 28 and 56 days. Lactic acid bacteria populations were recorded in fresh forage varying from 3.93 (30 days of regrowth) to 5.51 (70 days of regrowth) log colony-forming units (cfu)/g forage. Maximum populations of these microorganisms were recorded in the silages on the seventh day of fermentation (8.69 log cfu/g silage). Enterobacteria populations persisted until the 28th day, with maximum values found as early as the first day of fermentation (7.89 log cfu/g silage). Levels of DM, NDF, ADF and ADIN increased linearly whereas values of CP decreased linearly with age of regrowth of the plants. There was a linear reduction in the levels of DM, CP and NDF and linear increase in the levels of ADIN over the period of fermentation. N-NH3 level decreased and increased linearly with regrowth age and fermentation period, respectively. The pH decreased exponentially with fermentation period. Lactic acid increased and butyric acid decreased linearly with regrowth age. The predominant Lactobacillus plantarum species in signalgrass plants is Lactobacillus plantarum.

Highlights

Enterobacteria populations persisted until the 28th day, with maximum values found as early as the first day of fermentation (7.89 log cfu/g silage)
There was a linear reduction in the levels of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) and linear increase in the levels of acid detergent insoluble nitrogen (ADIN) over the period of fermentation
The potential of a plant for silage depends on its original level of humidity, which should be close to 70% of the soluble carbohydrate content, and of the low buffer power, which should offer no resistance to the reduction of the pH to values from 3.8 to 4.0 (McDonald et al 1991)

Summary

Introduction

The potential of a plant for silage depends on its original level of humidity, which should be close to 70% of the soluble carbohydrate content (above 8% in the DM), and of the low buffer power, which should offer no resistance to the reduction of the pH to values from 3.8 to 4.0 (McDonald et al 1991). The development and predominance of groups of microorganisms take place at different stages of this process following a succession of microorganisms that are directly related to the O2 concentration and the medium pH (Meeske et al, 1999). Grasses are colonized by a large numbers of lactic acid bacteria. Different species occur simultaneously in the same culture (Daeschel et al, 1987). According to Pahlow et al (2003), in a review paper, the most commonly species found in plants are the Lactobacillus plantarum, Lactobacillus casei, Pediococcus acidilactici and Enterococcus faecium. Some heterofermentative lactic acid bacteria may be found in such medium

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