Effect of rehydration and silage storage period of corn with medium vitreous endosperm on chemical composition and dry matter in situ degradability

Abstract Text: The aim of this study was to evaluate the effects of rehydration process and storage period of milled, rehydrated and ensiled corn (MREC) with medium vitreousness (67 ± 3%) on chemical composition and in situ DM degradability. Corn grains were harvested with 83% DM concentration and dried to obtain 87% DM concentration. After dried, corn grains were milled (2 mm), rehydrated to 67% DM, and ensiled (silo density of 880 kg/m³) in mini-silos. Furthermore, the MREC samples were evaluated in different storage periods (3 to 330 d). The MREC were analyzed for nutrient contents, fermentation products and in situ DM degradability. The data were modeled according to Mehrez and Ørskov (1977), and the effects of MREC storage time on degradability were evaluated by the MIXED procedure of SAS (α = 0.05), in a completely randomized design with two replications. No effect of ensiling period was observed for MREC DM and CP content. The ensiling period reduced the MREC starch content (P<0.001). The MREC starch content was 2.4 percentage points lower in the silos with 330 days of storage compared to the silos with 3 days of storage. The MREC with 330 days of storage had greater (P<0.001) concentrations of NH₃-N, ethanol, lactate, acetate, propionate, and butyrate were increased by 8.5, 2.4, 3.45, 4.1, 1.7, and 2.8 folds, respectively. Likewise, the storage time of MREC increased (P<0.001) in situ DM degradability. The percentage of rapidly degradable DM fraction (fraction A), the degradation rate of the slowly degradable DM fraction (fraction C) and the potentially degradable DM (pD) were increased by 3.04, 2.42 and 1.009 folds after 330 days of storage. The C fraction (slowly degradable DM fraction) from the MREC stored for 330 days decreased by 1.91 fold in comparison to the MREC stored for 3 days. The effective DM degradability, which was adjusted for rumen passage rates of 0.02, 0.05 and 0.08 %/h, increased (P<0.001) from 81 to 93.3%, from 66.6 to 88.6%, and from 57.6 to 84.9%, respectively. In conclusion, the storage period affected the chemical composition and increased the in situ DM degradability of MREC with medium vitreous endosperm.

Keywords: Ensiling. In situ Degradability. Vitreousness.