Nutritive value and storage characteristics of large-round bales of alfalfa-grass or perennial-grass hays treated with a propionic acid–based preservative at elevated application presets

Abstract

Our objectives were to evaluate the storage characteristics and changes in nutritive value for large-round bales of alfalfa (Medicago sativa L.)-orchardgrass (Dactylis glomerate L.) or perennial-grass [orchardgrass; tall fescue (Festuca arundinacea Shreb.); meadow fescue (Festuca pratensis Huds.)] hays treated with a propionic acid–based preservative. Applicator delivery presets were increased by 50% relative to standard factory settings, and hays were compared against untreated control hays. In Exp. 1, 21 large-round bales (1.2 × 1.5 m; 30.5 ± 1.40% moisture; 88% alfalfa, 12% grass) were produced in a completely randomized design with 2 treatments. Bales either received a propionic acid–based preservative at 1.0 ± 0.41% of wet bale weight (n = 11), or no preservative (n = 10), and were stored outdoors on wooden pallets for 131 d. Experiment 2 was conducted similarly; 26 bales of mixed, perennial-grass hay (1.2 × 1.5 m; 18.4 ± 1.40% moisture) were either treated with a preservative at 0.25 ± 0.104% of wet bale weight (n = 15) or were untreated (n = 11) and stored in an identical manner for 40 d. In Exp. 1, application of the preservative reduced maximum internal bale temperatures during the first 30 d of storage compared with untreated control hays (51.8 vs. 60.6°C; P < 0.001); similarly, heating degree days >30°C (HDD) were less for treated hays during the same initial (30-d) time interval (441 vs. 716 HDD; P = 0.001). However, total HDD after 131 d of storage did not differ across treatments (P = 0.426), largely because of the tendency for greater accumulated HDD in treated bales from 31 to 131 d in storage (1,105 vs. 761 HDD; P = 0.085). Final energy density (NEl) was greater (P = 0.030) for treated hays compared with untreated control hays (1.26 vs. 1.21 Mcal/kg DM), but both treatments were depressed from initial prestorage estimates (overall mean = 1.37 Mcal/kg DM). For Exp. 2, there were no differences (P ≥ 0.185) between treatments for any poststorage measure of nutritive value. For bales made at 30.5% moisture, application of a propionic acid–based preservative with elevated delivery presets effectively reduced spontaneous heating during the first month of bale storage, and modestly improved poststorage energy density; however, any nutritional benefit from treatment was modest, and energy density was still subject to measurable reductions relative to prestorage estimates.