Storage characteristics of baled alfalfa-grass forages treated with a propionic-acid-based preservative or wrapped in stretch plastic film

Abstract

The objectives for this study were to assess the storage characteristics of relatively dry, mixed-species forage preserved with a propionic-acid-based preservative, or by wrapping with 7 layers of plastic film as baled silage. The experimental design was a randomized complete block with a 2 × 2 factorial arrangement of treatments, which included application of a propionic-acid-based preservative at 0.27 ± 0.025% of wet bale weight (yes or no), and wrapping in 7 layers of stretch film (yes or no). A total of 33 round bales (1.2 × 1.5 m) containing 66% legumes (alfalfa; Medicago sativa L.) and 31% grasses (orchardgrass; Dactylis glomerata L.) were produced at 25.8 ± 2.20% moisture. This number of bales were sufficient for 8 complete field blocks (replications), plus one additional bale assigned to receive preservative, but no plastic wrap. Bales were positioned on wooden pallets for 84 d before final sampling. Internal bale temperatures were monitored daily during the 84-d storage period. The preservative had no clear statistical effect on any measure of spontaneous heating ( P ≥ 0.086). In contrast, application of plastic film yielded reduced maximum internal bale temperatures (41.5 vs. 61.6°C; P < 0.001) and total heating degree days >30°C (111 vs. 732; P < 0.001) when compared with unwrapped bales. These reductions in spontaneous heating also were reflected in measures of nutritive value, where NE l was reduced in unwrapped bales by 9.2% ( P < 0.001), but only by a calculated 1.4% ( P > 0.05) in wrapped bales compared with pre-storage values. The application of plastic film onto relatively dry mixed-species forages proved extremely effective in reducing spontaneous heating during storage, as well as minimizing nutrient losses.