Abstract
The degree of anaerobiosis and its maintenance over the conservation period are key factors in obtaining high quality silage. There is currently a demand to replace petroleum-based plastic films with biodegradable materials with suitable mechanical properties. This work has evaluated, under outdoor conditions, the shelf life of a Mater-Bi® biodegradable plastic (MB) film and its effects on the fermentative characteristics, microbial counts and aerobic stability of corn silage, and compared it with commercially available polyethylene (PE) and high oxygen barrier (OB) films. Corn (409 g DM/kg) was ensiled in 30 drive-over piles covered with MB, PE or OB films. The piles were opened after 21, 85, 133, 195 and 230 d of conservation. The effect of the film was assessed in silage sample close to (CF) and far (FF) from the film. The OB film allowed high quality corn silages to be obtained with similar pH, lactic acid, yeast and mold counts for CF and FF during the entire 230 d of conservation. The PE film showed similar values for the FF and CF areas for the first conservation period (until 133 d). The MB film showed a similar silage quality to OB until day 85, after which it underwent biodegradation and lost its ability to preserve silage in a good state.
Highlights
Whole-plant corn silage has become the predominant forage to provide fibre and energy in dairy cattle diets, and it is generally conserved worldwide through ensiling [1]
After 85 days of conservation, the Mater-Bi® biodegradable plastic (MB) film began to biodegrade, and this led to a depletion of the fermentative products, an increase in the yeast and mold counts and a decrease in aerobic stability. These results indicate that the use of MB is not useful to avoid the aerobic deterioration of corn silage after about 3 months
The different types of plastic film used to cover silages is a key factor in obtaining a high quality silage, because they can determine different degrees of anaerobiosis in a bunker silo
Summary
Whole-plant corn silage has become the predominant forage to provide fibre and energy in dairy cattle diets, and it is generally conserved worldwide through ensiling [1]. The degree of anaerobiosis reached in the filled silo and its maintenance over the entire conservation period are key factors in obtaining a high quality silage [3,4]. The ensiling technique requires an absolutely air-tight environment which, until the fifties, could only be attained through the use of constructions made of concrete or steel. In those structures, silages were either not covered or covered with organic material, such as manure, with high concerns about the microbial quality of the silages. The introduction, in the early 1950s, of plastic sheeting to cover silage was a milestone of great significance [6] and most silages were covered from the beginning of the 1960’s until 2000 with plastic film based on low density polyethylene (PE) [7,8]
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