Storage characteristics, nutritive value, and fermentation characteristics of alfalfa packaged in large-round bales and wrapped in stretch film after extended time delays

Authors: Coblentz, Wayne; COFFEY, KENNETH - University Of Arkansas; CHOW, EDGARD - Kuraray America, Inc

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2015
Publication Date: 4/20/2016
Publication URL: https://handle.nal.usda.gov/10113/62363
Citation: Coblentz, W.K., Coffey, K.P., Chow, E.A. 2016. Storage characteristics, nutritive value, and fermentation characteristics of alfalfa packaged in large-round bales and wrapped in stretch film after extended time delays. Journal of Dairy Science. 99:3497-3511.

Interpretive Summary: The production of baled silage is attractive to many small or mid-sized dairy producers because it offers a number of advantages over conserving forages as dry hay. Perhaps the most important advantage is the reduced risk of rain damage to forage crops because the time required for wilting to a recommended moisture threshold for this silage type is greatly reduced relative to dry hay. Our objectives were to test a prototype bale wrap containing an oxygen-limiting barrier against an identical commercially available bale wrap produced without the oxygen barrier. The scope of the study was increased by varying the length of time before wrapping the large-round bales of alfalfa; they were wrapped within 4 hours of baling (recommended), or after delays of 1, 2, or 3 days. Inclusion of an oxygen barrier had no effect on nutritive value or silage fermentation; however, the number of film layers (7) was relatively conservative for most production situations. Generally, silage fermentation was impaired by wrapping delays (especially beyond 24 hours), resulting in reduced production of fermentation acids and a less-acidic final silage pH. Internal bale temperatures were elevated when wrapping was delayed, resulting in a poorer feed quality of the silages (increased concentrations of fiber components and reduced energy densities). From a practical standpoint, round bales should not be exposed to air for more than 24 hours before wrapping in plastic film; longer delays will negatively impact silage fermentation and silage quality. This information will help forage growers produce baled silage that is of good quality with methods that are economically sustainable.

Technical Abstract: The production of baled silage is attractive to producers because it offers advantages over dry hay, particularly by limiting risks associated with wet or unstable weather conditions. Our objectives were to test the effects of delayed wrapping on silage fermentation, storage characteristics, and the nutritive value of baled alfalfa silages. To accomplish this, large-round bales of alfalfa were wrapped in plastic film within 4 h of baling (d 0), or after delays of 1, 2, or 3 d. A secondary objective was to evaluate a prototype bale wrap containing an O2-limiting barrier (OB) against an identical polyethylene wrap without the O2 barrier (SUN). Sixty-four 1.19 × 1.25-m bales of alfalfa were made from 4 field blocks at a mean moisture concentration of 59.1 ± 4.3% with a mean initial wet bale weight of 473 ± 26.4 kg. Two bales per field block were assigned to each combination of bale wrap (SUN or OB) and wrapping time (0, 1, 2, or 3 d post-baling), and one bale of each pair was fitted with a thermocouple placed in the geometric center of each bale. All bales were sampled after a 97-d storage period. Internal bale temperatures, recorded at the time bales were wrapped, were greater for all bales with wrapping delays compared to bales wrapped on d 0 (54.9 vs. 34.9oC), and increased to a maximum of 63.9oC after a 3-d delay exhibiting a linear effect of time delay. Total silage fermentation acids (lactic, acetic, propionic, butyric, and isobutyric) were greatest when bales were wrapped on d 0 compared to all bales wrapped with time delays (4.64 vs. 2.26% of DM), and declined with linear and quadratic effects of wrapping delay. Total fermentation acids also were related quadratically to internal bale temperature by regression [Y (% of DM) = 0.0042 x2 – 0.50 x + 17.1; R2 = 0.725]. Similar responses were observed for lactic acid, except that trends were linear, both for orthogonal contrasts evaluating length of wrapping delay, and in regressions on internal bale temperature [Y (% of DM) = - 0.046 x + 3.5; r2 = 0.663]. Butyric acid also was detected, regardless of treatment, but was greatest within bales wrapped on d 0 compared to those with wrapping delays (0.99 vs. 0.38% of DM), and a similar response (0.68 vs. 0.52% of DM) was observed for NH3-N, suggesting that clostridial activity occurred during silage fermentation. Based on these results, silage fermentation characteristics and the nutritive value declined with time delays before wrapping, but responses were exacerbated when delays exceeded 1 d.