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Meta-analysis of the effects of preservatives on hay spoilage II: Microbial inoculants.

M. Killerby




Meta-analysis of the effects of preservatives on hay spoilage II: Microbial inoculants.
M. Killerby*1, R. White2, D. C. Reyes1, A. Y. Leon-Tinoco1, S. Rivera1, H. Paz3, J. A. Jendza4, J. J. Romero1. 1Animal and Veterinary Sciences, School of Food and Agriculture, University of Maine Orono, ME, 2Animal and Poultry Sciences, Virginia Polytechnic Institute and State University Blacksburg, VA, 3Department of Animal and Dairy Sciences, Mississippi State University Starkville, MS, 4BASF Florham Park, NJ.

Our objective was to conduct a meta-analysis to evaluate the effects of preservatives on hay spoilage during storage. A literature search was conducted using the ISI Web of Science database. Microbial inoculants (82 treatments from 21 articles) were analyzed as a separate subset from chemical preservatives due to incompatibilities in application rate units (log cfu/fresh g vs. %, respectively). The metafor package of R statistical software was used to fit a multilevel linear mixed-effects model with response variables calculated as standardized mean differences (SMD) between treated and untreated samples within an experiment, within a study. Responses included DM loss, sugars, visual relative moldiness (MP) and hay maximum temperature (MT). Experiment and study were random effects. Moderators included forage type (FT: grass, legume, or mix); moisture class [MC: < 20% (low moisture) or > 20% (high moisture)] and application rate (AR). The 2- and 3-way interactions among moderators were also tested. Final models were selected using a backward selection procedure where non-significant variables were removed iteratively. In low moisture hay, predicted DM losses increased by 2.61% units for each 2 log cfu/fresh hay g increase in AR but no changes were observed in high moisture hay (P = 0.005), which had an overall greater predicted DM losses relative to low moisture hay (7.25 vs. 2.57%; P < 0.001). Sugar concentration was higher in treated grasses compared with legumes (SMD = 7.78 vs −1.10; P < 0.001). Furthermore, predicted sugar concentration increased by 1.32% DM units in high moisture hay and decreased by 0.387 in low moisture hay for each 2 log cfu/g increase in AR (P < 0.001). Predicted MP increased by 17.1% units for each 2 log cfu/g increase in AR across both moisture classes (P < 0.001) and a higher MP was observed in high vs. low moisture hay (41.2 vs. 14.0%; P < 0.001). In high moisture hay, legumes had a higher predicted MT than grasses (47.0 vs. 39.3�C) but in low moisture hay an opposite trend was observed (26.7 vs. 33.8; P = 0.001). High moisture legume hay is more susceptible to spoilage than grasses and inoculants evaluated failed to prevent spoilage.

Keywords: hay, inoculants, meta-analysis.