Novo método de vedação no controle da deterioração aeróbia de silagens de milho estocadas em trincheira

Abstract

Spoiled silage at the shoulders of bunker silo is a common sight. The objective of this study was to evaluate the effect of two systems for covering corn silage in bunker silos. The first system comprised a sheet of 45-µm-thick oxygen barrier film (OB, polyethylene+ethylene-vinyl alcohol) placed along the length of the sidewall before filling, with approximately two meters of excessdraped over the wall. After filling, the excess film was pulled over the wall, and a sheet of polyethylenewas placed on top. The second system involved using a standard sheet (ST) of 180-µm-thick polyethylene film. Eight commercial bunker silos were divided into two parts lengthwise so that half of the silo was covered with OB and other with ST system. During the filling, three bags with chopped corn were buried in the central part of the bunkers (CORE) in three 10-m-apart sections. After filling, eighteen bags (9 per covering system) were buried in the upper layer of the three sections. These bags were placed at three distances from the bunker walls (0 to 50, 51 to 100 and 101 to 150 cm). During unloading, the bags were removed from the silos to determine the dry matter (DM) losses, fermentation end-products and nutritive value. The Milk2006 spreadsheet was usedto estimate milk per ton of DM.The experiment was set up as randomized blocks with eight replicates (silos). Two orthogonal contrasts were tested to compare silages under the two covering system with that in the CORE (OB versus CORE and ST versus CORE). Three orthogonal contrasts compared the distances from the bunker walls (OB50 versus ST50, OB100 versus ST100 and OB150 versus ST 150). Variables were analyzed with the PROC MIXED procedure of the SAS at 5%. OB method produced wellfermented silages, which were similar to CORE, whereas PE system showed less lactic acid and greater pH and molds counts compared with CORE. PE method had 116.2 kg of milk/ton less than CORE (P = 0.0016), as OB system and CORE were similar (1258.3 and 1294.0 kg/ton, respectively). Regarding the distances from the walls, the effects were more pronounced in the corner zones (0 to 50 cm). OB50 silages had better fermentation profile and lowerspoiled microorganisms and DM losses than ST50. Corn silage at the shoulders has its quality similar to CORE when OB system is used.