Como a disponibilidade do amido da silagem de milho é afetada pelo atraso na ensilagem, densidade da silagem e tempo de armazenagem?

Abstract

The current study was carried out to investigate the effects of delayed ensiling, silage density and storage time on starch availability in corn silage. A whole corn plant (hybrid Pioneer 3016VYHR) was manually harvested with approximately 30% of dry matter (DM). The corn forage was crushed by a stationary chopper and ensiled in mini-silos (PVC tubes). The experiment was carried out under a completely randomized design following the factorial scheme: 2 (corn forage was ensiled immediately after the cut (0 h) or after 24 h, to simulate a delay in the process) x 2 (silage density: 514 and 605 kg wet forage/m3) x 2 (storage times of silage: 30 and 120 d) with 4 replicates per treatment. After the silos were opened, the aerobic stability assay was carried out at room temperature for 10 days. Data were analyzed by the SAS mixed at 5% of probability. The analysis of the interaction among the factors studied (i.e., delayed ensiling, silage density, and storage time) showed that the starch content was higher in the corn silage produced with high density, regardless of the delayed ensiling (~27% based on DM; p = 0.002). Corn silage produced immediately after the cut, with high density and stored for 120 d exhibited the highest starch digestibility (91.6%; p < 0.001). The amount of digestible starch was higher in corn silage with high density, regardless of the delayed ensiling (p = 0.014). Delayed ensiling increased the content of neutral detergent fiber (NDF) in 2.8 percentage units, decreased NDF digestibility in 3.5 percentage units and decreased the estimated milk production (–78 kg t/DM; p < 0.05) from corn silage. Delayed ensiling accompanied of low silage density and storage for 120 d resulted in the highest DM losses of corn silage (p = 0.016). In general, the storage time was the determining factor to increase the aerobic stability of corn silage (p < 0.05). Good silage practices (i.e., ensiling corn forage immediately after the cut and using higher silage density), associated with long storage time are fundamental factors to increase starch availability in corn silage. The delay in ensiling depress the nutritional value and estimated milk production of corn silage. In order to increase aerobic stability of corn silage, the storage time must be 120 d.