Effects of corn treated with foliar fungicide on in situ corn silage degradability in Holstein cows

With increasing feed prices and decreasing profit margins livestock producers are constantly searching for ways to increase nutritive value of the feed in order to get more production per unit of feedstuff. The objective of this study was to assess the digestibility of corn silage made of corn plants treated with various foliar fungicide applications. Treatments were: control (CON), corn received no foliar fungicide application; 1X, corn received one application of pyraclostrobin foliar fungicide (PYR; Headline; BASF Corp.) at vegetative stage 5 (V5); 2X, corn received 2 applications of foliar fungicides, PYR at stage V5, and a mixture of pyraclostrobin and metconazole (PYR+MET; Headline AMP; BASF Corp.) at reproductive stage 1 (R1); and 3X, corn received 3 applications of foliar fungicides, PYR at stage V5, PYR+MET at stage R1, and PYR+MET at reproductive stage 3. Corn was harvested at the same time and ensiled for 7 months. Dried unground corn silage was put into 288 (3 per time points/treatment/cow) 10×20cm bags and incubated for 8 different time points (0, 2, 4, 8, 12, 48, 72, and 96h). A sample of unground dried corn silage was also placed into 20×40cm bag and incubated for 48h. Digestibility of corn silages was estimated using in situ procedure with 3 rumen-cannulated lactating multiparous Holstein cows. The degradable fraction of dry matter (DM) tended to be greater (P=0.08) for corn silages treated with fungicide when compared with CON. There was no treatment effect (P>0.05) on neutral detergent fiber (aNDF), acid detergent fiber (ADF), starch, and crude protein (CP). However, the soluble fraction of DM, aNDF, and ADF decreased (P<0.05) as fungicide applications increased. Effective degradability (ED) was greater (P<0.05) in CON than corn silages treated with fungicide mainly due to decreased ED in 3X compared with 1X and 2X. In situ digestibility for bigger and smaller bags was different. Degradability of DM, aNDF, and ADF was higher (P<0.05), while starch and CP degradability was lower (P<0.01) in the larger bags. Fungicide application to corn for silage lead to higher DM degradable fraction which seems to be the result of increased sugar and starch along with decreased aNDF and ADF.