Effects of foliar fungicide and ensiling time on dry matter and in vitro digestibility of brown midrib and floury corn silage varieties

The objective of this study was to determine the effect of foliar fungicide (FUNG) and ensiling time on the in vitro digestibility of 2 corn silage (CS) varieties: brown midrib (BMR) and floury (FLY). Treatments were assigned to 16 plots in a completely randomized block split-plot design. Treatments were: BMR without FUNG, FLY without FUNG, BMR with FUNG, and FLY with FUNG. Fungicide (Headline AMP; BASF Corp.) was applied at vegetative tassel. Fresh-cut silage samples were collected at harvest and sealed inside vacuum seal bags using the Minipack MVS-20 single chamber vacuum sealer (Doug Care Equipment, Inc., Springville, CA). Mini silos were made for 4 separate time points: 0, 30, 90, and 150 d. Statistical analysis was performed using the MIXED procedure in SAS (v9.4). No significant 2- (variety × day, treatment × day, variety × treatment) or 3-way interactions (variety × treatment × day) were observed for CS dry matter (DM), neutral detergent fiber digestibility at 30 h (NDFD30), or undigested NDF (uNDF); P ≥ 0.13. Corn treated with FUNG had a lower DM % than corn in CON with 29.76 and 31.44 ± 0.35% DM, respectively; P = 0.006. NDFD30 and uNDF were not affected by application of FUNG; P ≥ 0.26. Brown midrib corn had a lower DM content than FLY corn with 29.58 and 31.62 ± 0.36 % DM, respectively; P = 0.002. Dry matter increased as ensiling time increased with 28.48, 30.34, 30.47, and 33.11 ± 0.48 % DM for 0, 30, 90, and 150 d ensiled, respectively; P < 0.0001. BMR NDFD30 was greater than FLY with 57.26 and 49.23 ± 0.69 % DM, respectively; P < 0.0001. NDFD30 was lowest when corn was ensiled for 0 d compared to 30, 90, or 150 with 50.77, 53.63, 55.53, and 53.05 ± 0.94 % DM, respectively; P = 0.007. BMR corn had a lower uNDF compared to FLY with 9.61 and 12.53 ± 0.21 % DM, respectively; P < 0.0001. Corn ensiled for 150 d had a lower uNDF compared to corn ensiled for 0, 30, or 90 d with 9.68, 11.67, 11.92, and 11.02 ± 0.29% DM, respectively; P < 0.0001. In conclusion, BMR corn silage had improved in vitro digestibility compared with FLY and 150 d ensiled compared to 0, 30, or 90 d based on improvements in NDFD30 and uNDF, however, application of FUNG exhibited no differences in plant in vitro digestibility.