Refining recommendations on preservative application for large-round bales of alfalfa hay

Authors: Coblentz, Wayne

Submitted to: Electronic Publication
Publication Type: Other
Publication Acceptance Date: 2/28/2019
Publication Date: 3/9/2019
Citation: Coblentz, W.K. 2019. Refining recommendations on preservative application for large-round bales of alfalfa hay. Electronic Publication. https://www.midwestforage.org/pdfRschProj/17-Coblentz.pdf.

Interpretive Summary:

Technical Abstract: Past studies at the University of Wisconsin Marshfield Agricultural Research Station have demonstrated that the effectiveness of propionic-acid-based hay preservatives vary considerably for 600-lb rectangular bales compared to 1200-lb large-round bales, with effectiveness being greater with smaller rectangular bales. Further studies have demonstrated that spontaneous heating is significantly reduced in 4-ft diameter round bales compared to larger 5-ft diameter bales when acid-based preservatives are applied. Our objectives for this experiment were to compare spontaneous heating responses within 5-ft diameter round bales of alfalfa hay that were either treated with CropSaver™ propionic-acid-based preservative applied with a Harvest Tec 647C Applicator (TREATED), or not treated with the preservative (CONTROL). Twenty-eight bales were analyzed; of these n = 16 were TREATED (mean wet weight = 465 ± 19.2 kg) and n = 12 were CONTROL hays (mean wet weight = 473 ± 22.7 kg). Bale moistures were 20.2 ± 2.39% for TREATED and 20.2 ± 1.96% for CONTROL hays; TREATED hays received 4.0 ± 0.57 lbs acid preservative/ton, which was consistent with the recommended application rate for this preservative product in this moisture range. Bales were stored outdoors on wooden pallets for 65 days, and internal bale temperatures were monitored daily. TREATED hays exhibited reduced mean internal bale temperatures compared to CONTROL hays at 30 days (37.9 vs. 42.3'; P = 0.007), and across the entire 65-day storage period (36.3 vs. 39.6'; P = 0.043). Heating degree days > 30' (HDD) accrued over the entire storage period also were reduced in TREATED hays (450 vs. 628 HDD; P = 0.043). Differences in heating characteristics on the basis of acid-application were further corroborated by greater dry matter (DM) recovery for TREATED hays (95.6 vs. 93.7%; P = 0.009). Changes (poststorage – prestorage concentrations) for fiber-related analytes during storage generally were limited in magnitude, but tendencies for less change in TREATED hays were observed for neutral detergent fiber (NDF; P = 0.090) and acid-detergent lignin (ADL; P = 0.066), and statistically less change (P = 0.037) was observed for hemicellulose. Crude protein (CP) associated with the cell wall (NDICP) increased sharply in all hays, but this response was greatest (P = 0.014) in CONTROL hays, which is consistent with the greater heating observed in those hays. Energy density was reduced in all hays in response to heating (mean loss = 4.1 TDN units), but did not differ (P = 0.121) on the basis of treatment. Overall, preservative application in large-round bales of alfalfa hay improved heating characteristics, DM recovery, and some nutritive analytes compared to CONTROL hays when applied at recommended rates, but these improvements were modest, and raise further questions about whether appropriate rates should be increased for large bale packages.