Nutritive value, silage fermentation characteristics, and aerobic stability of grass-legume round-baled silages at differing moisture concentrations with and without manure fertilization and microbial inoculation

Authors: Coblentz, Wayne; AKINS, MATTHEW - University Of Wisconsin; Jaramillo, David; CAVADINI, JASON - University Of Wisconsin

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2022
Publication Date: 11/25/2022
Citation: Coblentz, W.K., Akins, M., Jaramillo, D.M., Cavadini, J. 2022. Nutritive value, silage fermentation characteristics, and aerobic stability of grass-legume round-baled silages at differing moisture concentrations with and without manure fertilization and microbial inoculation. Journal of Animal Science. 100(11). https://doi.org/10.1093/jas/skac325.
DOI: https://doi.org/10.1093/jas/skac325

Interpretive Summary: The objectives of this research were to test the efficacy of an inoculant to mitigate production of clostridial products in high-moisture silage bales, where forages were treated with dairy slurry during the preceding growth cycle. Despite the application of dairy slurry, as well as greater-than-recommended bale moisture, only minimal concentrations of typical clostridial products were observed following fermentation. Inoculation had no effect on final concentrations of either NH3-N or butyric acid. The lack of clostridial response might be explained by numerous strong rainfall events during the growth of these forages, prompt wrapping following baling, substrate adequacy, as well as an exceptionally low buffering capacity, particularly for most mixed, legume-grass swards harvested at this location. As a result, the efficacy of using a combination hetero- and homolactic inoculant to mitigate clostridial activity was inconclusive. Both bale moisture and inoculation had positive effects on concentrations of acetic acid following fermentation, and resulted in numerically reduced counts of yeasts following a 34-d exposure to air: however, surface bale temperatures remained cool, regardless of treatment, largely in response to the cool ambient temperatures in central Wisconsin during November. Results from this study continue to provide recommendations for forage conservation practices that are relevant to livestock producers.

Technical Abstract: For baled silages, production of secondary clostridial fermentation products can be exacerbated by exceeding normal moisture targets (45 to 55%), and/or by application of dairy slurry during the preceding growth cycle. Our objectives were to test a microbial inoculant as a mitigant to limit formation of clostridial products in high-moisture, legume-grass baled silages that were treated with dairy slurry. A secondary objective was to examine the effects of bale moisture and inoculation on the aerobic stability of these fermented silages following exposure to air. A first-cutting, mixed-species stand was harvested as silage, and then three manure treatments were applied as a whole-plot treatment term: i) control (no manure); ii) slurry applied immediately to stubble (63,250 L/ha); or iii) slurry applied after a 1-week delay (57,484 L/ha). An interactive arrangement of bale moisture (64.1 or 48.4%) and inoculation (yes or no) served as a subplot term. The inoculant contained both homolactic (Lactococcus lactis 0224) and heterolactic (Lactobacillus buchneri LB1819) components. The experimental design was analyzed as a randomized complete block with 4 field blocks as replications, and the study included 48 experimental units (1.2 × 1.2-m round bales). Bales were wrapped with 7 layers of stretch plastic film and stored for 98 to 100 d before sampling. Fermentation was affected by slurry application strategies, but this was likely related to inconsistent bale moisture across slurry-application treatments. Concentrations of butyric acid were low, and there were no detectable contrasts comparing manure treatments (mean = 0.05%; P = 0.645). Bale moisture affected all measures of fermentation, with bales made at 64.1% moisture exhibiting a more acidic final pH (4.39 vs. 4.63; P < 0.001), less residual water-soluble carbohydrates (2.1 vs. 5.1%; P < 0.001), as well as greater lactic acid (4.64 vs. 2.46%; P < 0.001), acetic acid (2.26 vs. 1.32%; P < 0.001), and total fermentation acids (7.37 vs. 3.97%; P < 0.001). Inoculation also reduced pH (4.47 vs. 4.56; P = 0.029), and increased acetic acid (1.97 vs. 1.61%; P < 0.001) and 1,2-propanediol (1.09 vs. 0.72%; P < 0.001) compared to controls. During a 34-d aerobic exposure period, surface bale temperatures were affected only minimally, likely due to cool ambient temperatures; however, yeast counts were numerically lower in response to greater production of acetic acid that was stimulated by both high bale moisture and inoculation.