Abstract #W136

# W136
Effects of feeding floury and brown midrib whole-plant corn silage varieties from corn treated with foliar fungicide to lactating Holstein cows on nutrient digestibility.
L. J. Wente*1, M. S. Akins2, F. C. Cardoso1, 1Department of Animal Sciences, University of Illinois, Urbana, IL, 2Department of Dairy Science, University of Wisconsin-Madison, Marshfield, WI.

It is important to feed high-quality feedstuffs to lactating dairy cows to maximize productivity and economic return. Nutrient intake and digestibility are ways to assess the quality and production potential of these feeds. The purpose of this experiment was to determine the effects of feeding floury and brown midrib (BMR) whole-plant corn silage (WPCS) varieties from corn treated with foliar fungicide on nutrient digestibility in lactating Holstein cows. Thirty-two lactating cows [BW = 649 ± 74 kg; DIM = 189 ± 49 d] were randomized in a 4 × 4 Latin square design balanced to measure carryover effects. Treatments were floury WPCS with fungicide application (FF), floury WPCS with no fungicide application (FC), BMR WPCS with fungicide application (BF), and BMR WPCS with no fungicide application (BC). Corn was sprayed with fungicide (pyraclostrobin, C19H18ClN3O4 + metconazole, C17H22ClN3O; Headline AMP, BASF, Florham Park, NJ) at the vegetative tassel stage (VT). WPCS was inoculated (Silo-King; Agri-King, Fulton, IL) and allowed to ensile in Ag Bags (Ag Bag Systems, St. Nazianz, WI) for 295 d before feeding. Statistical analysis was conducted using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Cows in non-fungicide treatments had greater DM digestibility (74.35 ± 0.37%) than those in fungicide treatments (72.57 ± 0.37%; P < 0.01). Cows in non-fungicide treatments also had greater DMI (23.41 ± 0.72 kg/d) than cows in fungicide treatments (22.35 ± 0.72 kg/d; P < 0.01). Cows in BMR treatments had greater starch digestibility (93.16 ± 0.10%) than those in floury treatments (92.81 ± 0.10%; P < 0.01); cows in fungicide treatments had greater starch digestibility (93.21 ± 0.10%) than those in non-fungicide treatments (92.75 ± 0.10%; P < 0.01). Starch intake was greater for FC cows (6.24 ± 0.18 kg/d) than for FF cows (5.89 ± 0.18 kg/d; P < 0.01). Crude protein intake was greater for FC cows (4.21 ± 0.12 kg/d) compared with FF cows (3.63 ± 0.12 kg/d; P < 0.01). In conclusion, non-fungicide treatments had greater DM and starch digestibility compared with fungicide treatments.

Key Words: foliar fungicide, corn silage, digestibility