Abstract
Considering the hypothesis that density and dry matter (DM) concentration may be used as indicators of silage nutritional quality, the aim of the present study was to determine density and maturation stage (i.e. DM concentration) of corn silages under farm conditions in Brazil, establishing relationships between density and physical and chemical characteristics. In a completely randomized design, 20 bunkers of corn silage, each from a different farm, were used for data collection. Using a coring machine, 5 samples of silage were extracted from an exposed face of each silo and samples were analyzed for density of compaction, plus concentrations of DM, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), total digestible nutrients (TDN), total carbohydrate (TC), non-fiber carbohydrate (NFC) and starch (STA), as well as electrical conductivity. There was significant variation in many of the parameters measured with the greatest variation in density on a natural matter basis. Negative correlations were observed between percentages of DM, NDF and ADF in the silage and silage density on a natural matter basis (P<0.05). On the other hand, DM% was positively correlated with concentrations of STA, TDN and TC (P<0.05). Density on a DM basis showed positive correlation with STA but was negatively correlated with NDF and ADF (P<0.05) indicating that the more fibrous material is harder to compact. A technology transfer program seems warranted to inform Brazilian farmers of these findings and the importance of harvesting forage at a stage of growth when quality would be better to increase the probability of achieving adequate compaction of the ensiled material and hence better quality of material at feeding out.
Highlights
Major challenges for high quality silage production occur at the stages of ensiling, storing and discharging from bunker silos
The greatest variation was shown for DNM, being much greater than the variation in density on a dry matter basis (DDM), while the variation in total carbohydrates, total digestible nutrients (TDN) and pH was minimal as shown by standard deviation (SD) values below
Corroborating the idea that silage materials with high dry matter (DM)% usually present higher pH values (Senger et al 2005), our results showed that pH was affected by compaction levels (DNM = -0.30), with greater pH values in low density samples, which may be associated with poor nutritional quality of the silage and reduced acceptability by the animals
Summary
Major challenges for high quality silage production occur at the stages of ensiling, storing and discharging from bunker silos. During these stages, microbial activities may affect fermentation processes in the ensiled forage and its nutritional quality. To reduce quality losses, parameters related to the forage itself at the harvest stage, such as moisture content, crude protein concentration and particle size, must be evaluated as well as those related to the type of bunker silo, which will determine the exposure of the ensiled material to oxygen and compaction (Cardoso et al 2016). Silages with low density often contain high residual air mass, resulting in longer periods of oxygen exposure and increased consumption of soluble carbohydrates, plus reduced production of organic acids and higher pH (McDonald et al 1991). Greater compaction results in higher density, allowing a better retention of soluble carbohydrates and reduced proteolysis, resulting in improved acceptability to animals and nutritional quality of the ensiled material (Velho et al 2007; Sucu et al 2016)
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