Storage characteristics, nutritive value, and fermentation characteristics of large-round bales of alfalfa-mixed grass forage wrapped with different layers of stretch film

Authors: Coblentz, Wayne; Ogden, Robin; AKINS, MATTHEW - University Of Wisconsin; CHOW, EDGARD - Kuraray America, Inc

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2016
Publication Date: 11/28/2016
Citation: Coblentz, W.K., Ogden, R.K., Akins, M.S., Chow, E.A. 2016. Storage characteristics, nutritive value, and fermentation characteristics of large-round bales of alfalfa-mixed grass forage wrapped with different layers of stretch film. Professional Animal Scientist. 32:805-815.

Interpretive Summary: Baled silage, which is preserved by wrapping in layers of plastic, has become a popular form of forage conservation. However, many practical management questions have not been investigated thoroughly. The objectives of this study were to evaluate the number of polyethylene wrapping layers and the presence or absence of an oxygen-limiting barrier within the polyethylene wrap on the subsequent storage characteristics, nutritive value, and silage fermentation characteristics of alfalfa-mixed grass round-bale silages. Generally, round-bale silages packaged at 59.8% dry matter were adequately preserved by polyethylene wraps applied in 4, 5, or 6 layers, regardless of wrap type. Only minor differences in fermentation and nutritive value were observed in response to treatment. Mold and yeast counts should be responsive to oxygen permeability, but were frequently non-detectable. However, detectable counts occurred more frequently, and were substantially greater in magnitude, without the oxygen barrier; but bale numbers were inadequate to be statistically conclusive. Based on visual observation, the threat of silage being spoiled by exposure to oxygen from internal puncture by coarse alfalfa stems probably establishes a minimum threshold of 4 polyethylene layers for acceptable storage. The concept of an oxygen barrier may be viable, but the potential to reduce the number of layers needed may be limited by the potential for physical puncture from inside the bale. This information will help forage producers determine the minimal amount of plastic needed to successfully preserve silage.

Technical Abstract: Baled silage has become a popular form of forage conservation; however, many practical management questions have not been investigated thoroughly. Our objectives were to evaluate the number of polyethylene wrapping layers and the presence (OB) or absence (SUN) of an O2-limiting barrier within the wrap on the storage characteristics, nutritive value, and silage fermentation characteristics of alfalfa-mixed grass round-bale silages. Thirty-six 1.2 × 1.2-m large-round bales of a mixed sward comprised predominantly of alfalfa (Medicago sativa L.; 82 ± 3.8% alfalfa, DM basis) were packaged at 59.8 ± 3.2% DM and wrapped the same day with 4, 5, or 6 layers of the 2 polyethylene films (OB or SUN). Bales were sampled after 127 d at 0 to 0.15-m (SURFACE) and 0.15 to 0.61-m (CORE) depths. Generally, plastic type and number of wrapping layers had minimal effect on nutritive value and silage fermentation characteristics. However, greater concentrations of total fermentation acids, lactic acid, and NH3-N were found within the SURFACE compared to CORE layer (P = 0.03), but the titratable acidity (¯X = 15.4 mEq/kg DM; P = 0.27) and final pH (¯X = 5.70; P = 0.23) did not differ. Although yeast and mold counts at the SURFACE layer often were non-detectable (< 3.0 log10 cfu/g), elevated counts were most frequently associated with SUN. An O2-limiting barrier may improve anaerobic integrity at the surface layer of baled silages, but the potential to reduce polyethylene usage may be limited by the risk of internal physical puncture by coarse alfalfa stems.