Use of new plastic stretch films with enhanced oxygen impermeability to wrap baled alfalfa silage

The high permeability of polyethylene (PE) films to O2 seems to be one of the main drawbacks of wrapped bale silage. The aim of this work was to compare the microbial and fermentation quality of high dry matter (DM) content alfalfa bales wrapped with a commercial PE film (six layers) and with two new different stretch films (four layers) with 18‐ and 370‐fold lower permeability than PE (MB and HB, respectively). Four field trials were conducted near Turin, Italy, on alfalfa stands. After 420 d of bale storage, the fermentation profiles, bale surface covered by molds, mold and yeast counts, and DM losses were evaluated. Both oxygen barrier films reduced DM losses and mold spoilage in comparison to the commercial PE film. The bale surface covered by molds was kept below 15% with four layers of MB film, whereas it ranged from 20% to more than 50% with six layers of PE film. The more reduced O2 permeability of the HB film further reduced the surface mold, keeping it below 7%. The results show clearly that reduced film permeability to oxygen is a key factor in successfully ensiling alfalfa at high DM content in wrapped bales for long storage periods because it reduces plastic usage without increasing costs.