Effects of Irrigation Levels of Corn Silage Hybrids on Nutrient Profile and in Vitro Disappearances

Corn hybrids designed for silage were evaluated under different irrigation regimens effects on nutritional composition, fermentation losses, and aerobic stability. Corn silage hybrids (n = 6) were randomly assigned into plots (n = 8 per hybrid) divided under two irrigation systems (50 and 100 ET), totaling 48 experimental units (field plots). Forages for all plots were mechanically harvested on the same day, sampled, and ensiled into laboratory experimental silos (18.93 L units with sand in bottom for effluent collection and gas valve on top for gas release) and stored for 98 d. An aerobic stability test was conducted during post silo opening period, with measurements taken at 5, 10, and 15 d. A complete randomized design was used to compare the effects of irrigation level, hybrids, and potential interactions on variables of interest. Data were analyzed using the GLIMMIX procedures of SAS. Upon forage harvesting, DM content of hybrids tended (P = 0.08) to interact with irrigation level, where most of the hybrids under irrigation 50ET had 2 to 6 percent units of DM greater than those under 100 ET. Still at ensiling moment, lower (P = 0.01) pH and greater (P = 0.01) particle size were observed for forages under irrigation 50 ET compared with 100 ET, respectively, regardless of hybrid type. After fermentation period, only subtle differences (P = 0.05) on silage pH were observed, in which all of hybrids and irrigation levels showed desirable pH averages for silage. Hybrids submitted to 50 ET irrigation treatment tended (P = 0.10) to provide drier silages than those at 100 ET. Tendencies (P = 0.08) were also observed for hybrids fermentation losses (DM and gas), regardless of irrigation level (P ≥ 0.81). Silage time to break aerobic stability was not affected (P ≥ 0.14) by treatments; whereas regardless of hybrid type, silages that passed by hydric-stress showed lower pH during post-opening compared to 100 ET treatments. In vitro true digestibility of silages were not affected (P = 0.22) by treatments, averaging 78%. Corn silage hybrids assessed appear to preserve high nutritional value even when submitted to hydric stress. Corn crops assessed under restricted irrigation may require earlier harvesting time due to drier plants; whereas fermentation losses may be more dependent of hybrid type rather than irrigation level. Imminent post-opening of silos (0-5 d) appears to be more stable for hybrids that passed by water restriction.