Storage characteristics and nutritive value of moist large-round bales of alfalfa or alfalfa–grass hay treated with a propionic acid–based preservative

Abstract

ABSTRACT Objectives Our objectives for 2 experiments were to evaluate storage characteristics and changes in nutritive value for large-round bales of alfalfa or alfalfa–grass hays made with or without a propionic acid–based preservative. Materials and Methods In Exp. 1, 18 large-round bales (83% alfalfa, 17% mixed grass) were produced (20.6% moisture) in a randomized complete block design with a 2 × 3 factorial arrangement of bale diameters (1.2 or 1.5 m) and preservative-application strategies (fully automated, fully automated assuming a constant baling rate, or control). For Exp. 2, 28 (1.5-m diameter) large-round bales of alfalfa hay were produced in an unbalanced, completely randomized design (20.2% moisture; 16 acid treated, 12 controls). Results and Discussion For Exp. 1, all measures of spontaneous heating differed (P ≤ 0.037) between the 1.2- and 1.5-m bale diameters, with the larger diameter exhibiting greater maximum internal bale temperatures (46.1 vs. 41.6°C; P = 0.012) and greater total heating degree days >30°C (HDD) during storage (334 vs. 106 HDD; P = 0.024). In Exp. 2, all 16 acid-treated bales initially exhibited heating suppression relative to control hays but differed only numerically for total HDD (450 vs. 628 HDD; P = 0.223) after storage; within acid-treated hays, 9 of 16 bales incurred a secondary heating response, primarily after 25 d in storage. Implications and Applications Bale size has a strong effect on preservative effectiveness, and the secondary and extended heating responses exhibited by some acid-treated hays partially explains the mixed overall responses to preservative application noted in some previous experiments.