Effect of particle size on storage time of hydrated corn grain

Dry ground corn kernels are widely used as sources of energy readily available for microbial synthesis in the rumen. The objective of the present study was to measure the effect of particle size on the storage length of rehydrated and ensiled corn grain. Commercial corn was milled in 2-, 4-, 6-, 8-, and 10-mm sieves, rehydrated until reaching 65% DM, and ensiled for 14, 28, and 56 days, in a completely randomized design with a 5 x 3 factorial arrangement, with six replications per treatment. PVC mini-silos were used, with dimensions of 25 cm height x 10 cm of diameter. The variables DM, MM, CP, NDF, ADF, pH, molds and yeasts count, fermentative losses, in vitro degradability and aerobic stability were subjected to analysis of variance. The Tukey test was used to compare means. LAB counts was subjected to Wilcoxon's nonparametric test, considering significance at p < 0.05. Rehydrated corn silages with smaller particles (2 and 4 mm) showed higher LAB and mold counts, higher levels of CP and EE and higher density at opening silos than that of coarser particles. However, they showed lower percentages of DM, and were susceptible to microbial attack and faster temperature increases than were coarse particles during the chosen storage times. Silage subjected to 56 days of fermentation showed lower contents of NDF, ADF and CP, lower gas losses and lower pH values in aerobiosis, and increased levels of soluble protein (A + B1 fractions), losses effluents, number of hours to reach maximum temperature, and time to break aerobic stability. Coarse-grind silages subjected to 56 days of storage showed better chemical composition, lower LAB and mold counts, and less susceptibility to microbial degradation when exposed to air.