Nutritive value and fermentation characteristics of round-baled alfalfa-orchardgrass forages ensiled at various moisture concentrations with or without baler cutting engagement

Authors: COBLENTZ, WAYNE; AKINS, MATTHEW - UNIVERSITY OF WISCONSIN

Submitted to: Applied Animal Behaviour Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2019
Publication Date: 3/20/2019
Citation: Coblentz, W.K., Akins, M.S. 2019. Nutritive value and fermentation characteristics of round-baled alfalfa-orchardgrass forages ensiled at various moisture concentrations with or without baler cutting engagement. Applied Animal Behaviour Science. 35(2):135-145. https://doi.org/10.15232/aas.2018-01837.
DOI: https://doi.org/10.15232/aas.2018-01837

Interpretive Summary: The fermentation of baled silages is generally restricted because forages are frequently drier than precision-chopped silages, and usually wrapped in long-stem form. Our objectives were to compare the silage fermentation characteristics and nutritive value of cut and uncut alfalfa/orchardgrass baled silages packaged at high moisture (> 60%), and also to evaluate fermentation responses of baled silages made at typical moisture concentrations. Engagement of the bale-cutting mechanism improved initial wet bale weights (668 vs. 641 kg), but differences for initial dry bale weights and DM density were numerical only, and not statistically significant. Cutting the forage prior to ensiling offered little discernable improvement to forage nutritive value. Modest improvements were noted with respect to production of lactic acid, percentage of total VFA comprised of lactic acid, and (more acidic) final silage pH. For the silages in this study, the cumulative effects of improved fermentation within cut forages represented modest pH declines of about 0.10 to 0.16 pH units over initial bale moistures ranging from about 40 to 70%.

Technical Abstract: The production of baled silages is increasingly popular; however, some management considerations and/or fermentation characteristics of these silages are notably different from traditional precision-chopped silages. Fermentation is generally restricted in baled silages because these silages are frequently drier, and usually are wrapped in long-stem form. Our objectives were to compare the silage fermentation characteristics and nutritive value of cut and uncut alfalfa (Medicago sativa L.)/orchardgrass (Dactylis glomerata L.) baled silages packaged at relatively high moisture concentrations (> 60%), and also to evaluate fermentation responses of these baled silages made at typical moisture concentrations. Thirty-one 1.2 × 1.2-m round bales made from a mixed alfalfa/orchardgrass stand (56.5% alfalfa; 42.7% orchardgrass) were baled with or without engagement of the bale-cutting system over 4 bale-moisture groupings (67.5, 61.5, 51.1, and 45.8%, or high, moderately high, ideal, and dry, respectively). Engagement of the bale-cutting mechanism improved initial wet bale weights (668 vs. 641 kg), but only numerical differences were observed for initial dry bale weights (287 vs. 278 kg) and initial DM density (192 vs. 188 kg DM/m3). Initial DM density increased in an inverse relationship with bale moisture; bales made at moderately high moisture exhibited greater DM densities than high-moisture bales (180 vs. 152 kg DM/m3), and bales made at ideal moisture were more dense than all wetter bales collectively (207 vs. 166 kg DM/m3). Overall, the effects of initial bale moisture and cutting had little meaningful effect on silage nutritive value, except that silage fermentation reduced concentrations of neutral-detergent insoluble CP (% of CP) compared to pre-ensiled forage by 48 to 68%. Following fermentation, modest improvements were noted within cut bales for lactic acid, percentages of total VFA comprised of lactic acid, and a more acidic final silage pH. Final silage pH was best related to initial bale moisture with a simple linear model for both cut (Y = - 0.031 x – 7.50; R2 = 0.847) and uncut (Y = - 0.033 x + 7.74; R2 = 0.869) silages. Tests of homogeneity of slopes and intercepts indicated that slopes did not differ on the basis of bale-cutting engagement, but intercepts were different. For the alfalfa/orchardgrass silages in this study, the cumulative effects of improved fermentation within cut forages represented pH declines of about 0.10 to 0.16 pH units over initial bale moistures ranging from about 40 to 70%.