Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2012
Publication Date: 3/22/2013
Publication URL: http://handle.nal.usda.gov/10113/55973
Citation: Coblentz, W.K., Coffey, K.P., Young, A.N., Bertram, M.G. 2013. Storage characteristics, nutritive value, energy content, and in-vivo digestibility of moist large-rectangular bales of alfalfa-orchardgrass hay treated with a propionic-acid-based preservative. Journal of Dairy Science. 96:2521-2535. Interpretive Summary: Past studies have shown clear benefits from applying propionic-acid-based preservatives to alfalfa hay made in 100-lb small-rectangular bales, but their effectiveness within larger hay packages is not well defined. A recent study at this station conducted with 5-ft diameter round bales demonstrated that propionic-acid-based preservatives performed poorly with that bale type. However, large-rectangular balers use a different (plunger) packing mechanism, and our goal was to see if propionic-acid-based preservatives performed better under these conditions. Preservative was applied to large-rectangular bales of alfalfa-orchardgrass hay at bale moistures ranging from 19.6 to 27.4%; acid application rates were 0, 0.6, or 1.0% of wet bale weight. The acid preservative limited spontaneous heating in these hays, and results were impressive, regardless of initial bale moisture. Modest benefits also were observed for post-storage nutritive value of hays, as well as apparent digestibilities of dry matter and organic matter in growing lambs. These results suggest that the effectiveness of buffered propionic-acid-based preservatives may be dependent on bale type, and that spontaneous heating can be limited, and nutrients can be preserved, by using these preservatives within large-rectangular bale packages.
Technical Abstract: Unstable weather, poor drying conditions, and unpredictable rainfall events often place valuable hay crops at risk. Recent research with large-round bales comprised of alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) has shown that these large-bale packages are particularly sensitive to spontaneous heating and DM losses, as well as other undesirable changes with respect to forage fiber, protein, and energy density. Various formulations of organic (primarily propionic-acid-based) acids have been marketed as preservatives, normally for use on hays that are not desiccated adequately in the field in order to facilitate safe bale storage. Our objectives for this study were to: i) evaluate the efficacy of applying a commercial (buffered) propionic-acid-based preservative at 3 rates (0, 0.6, and 1.0% of wet-bale weight) to hays baled at 3 moisture concentrations (19.6, 23.8, and 27.4%) on the subsequent storage characteristics and post-storage nutritive value of alfalfa-orchardgrass forages packaged within large-rectangular (285-kg) bales; and then ii) evaluate the in vivo digestibility of these hays within growing lambs. Over a 73-d storage period, the preservative was effective at limiting spontaneous heating within these hays, and there was a clear effect of application rate for the wettest (27.4%) bales. For drier hays, both acid-application rates (1.0 and 0.6%) yielded comparable reductions in heating degree days > 30oC (HDD) relative to untreated controls. Unfortunately, reductions in spontaneous heating could not be associated with measurable improvements in recovery of forage DM after storage. Most changes in nutritive value during storage were related to measures of spontaneous heating in simple linear regression relationships; this suggests that improvements in nutritive value compared to untreated controls hays were largely associated with perturbations of normal heating patterns resulting from acid treatment at baling. Although somewhat erratic, apparent digestibilities of both DM (Y = -0.0080x + 55.6; r2 = 0.452) and OM (Y = -0.0085x + 55.5; r2 = 0.530) evaluated in growing lambs also were directly related to HDD in simple linear relationships. Based on this research, applying propionic-acid-based preservatives to large-rectangular bales is likely to provide good insurance against spontaneous heating during storage, as well as modest benefits with respect to nutritive value and digestibility.