The chemical composition, fermentation profile, and microbial populations in tropical grass silages

João Paulo Sampaio Rigueira,Karina Guimarães Ribeiro,Hilário Cuquetto Mantovani,Mariele Cristina Nascimento Agarussi,Odilon Gomes Pereira

doi:10.1590/s1516-35982013000900002

João Paulo Sampaio Rigueira, Karina Guimarães Ribeiro + Show 3 more

Open Access

https://doi.org/10.1590/s1516-35982013000900002

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Abstract

The objective of this study was to evaluate the fermentation profile, chemical composition and microbial population and losses in the silages of signalgrass and Mombasa grass fertilized with the following levels of nitrogen (N): 0, 30, 60 and 90 kg/ha. The grasses were harvested at 70 days of regrowth, chopped and then ensiled in laboratory silos that had 20 kg of capacity and a snap-top cover and were fitted with Bunsen valves. Before ensiling, samples of the plants were used for the isolation and identification of lactic acid bacteria (LAB) in epiphytic microbiota. The design adopted was a 4 × 2 factorial arrangement, with four doses of N and two forage species, in a completely randomized design, with four replicates. The predominant species of LAB was Lactobacillus fermentum. The interaction between the N dose and forage species affected the dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and water soluble carbohydrates (WSC) of the silages. The pH values and gas losses were influenced only by the forage species, with higher values for the Mombasa grass. For the ammonia (NH3-N) levels and effluent losses, there was an effect of the interaction between the forage species and N doses, and the highest values of NH3-N and effluent losses were found in the Mombasa grass silage fertilized with 60 kg N/ha. Nitrogen fertilization reduces the levels of DM and WSC in the silages and also increases the levels of CP, NH3-N and effluent losses.

Highlights

The excess forage produced by the perennial species in the rainy season must be conserved and should be considered a potential forage resource for feed in the dry season.Grass silages of the genus Panicum and signalgrass have constituted two of the most widely used roughages in the feedlots of Brazil
Detailed evaluations have indicated that a kilogram of total digestible nutrients (TDN) from grass silage is more expensive than TDN from corn silage (Pereira et al, 2007)
The lowest dry matter (DM) content in the Mombasa grass fertilized with 60 kg N/ha was likely due to methodological errors

Summary

Introduction

Grass silages of the genus Panicum and signalgrass have constituted two of the most widely used roughages in the feedlots of Brazil. In 2006, data indicate that grass silages were used by 18% of the 50 largest beef cattle feedlots in Brazil (Agripoint, 2007). The grass silages have some interesting advantages, such as a high annual productivity per area, perenniality, a low risk of loss, and greater harvest flexibility (Gonçalves et al, 2004). When compared with corn or sorghum silages, the grass silages have unfavorable aspects, such as a low content of soluble carbohydrates necessary for proper fermentation, low dry matter content at the time of cutting, high buffering capacity and lower energy content (Keady et al, 2008). Assuming that the potential for biomass production must be achieved, the use of nitrogen can be a viable alternative for enhancing the production of dry matter

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