Effects of Kernel Processing of Corn Silage with and without the Brown Midrib Trait on Nutrient Digestion By Finishing Steers

The effect of kernel processing and corn silage hybrid were evaluated for digestion by beef cattle fed dry rolled corn-based diets with 40% silage inclusion. Six ruminally fistulated steers (518 ± 40 kg) were used in a 126-d metabolism study in a 6×6 Latin Square design. Three corn silage hybrids were evaluated (CON; hybrid TMF2H708), a brown midrib hybrid (bm3; hybrid F1557952), and Unified™ corn silage with SilaSoft™ kernel technology, which was a brown midrib with a floury endosperm (bm3-EXP; hybrid F15578XT). The treatment design was a 2×3 factorial with the three hybrids and kernel processed or not. Silage was included in the diet at 40% on a DM basis. Each period was 21 d, which included a 14-day adaptation period followed by a 7-day collection period. Titanium dioxide was intraruminally dosed from days 10-21 as digestibility marker. Fecal samples were collected days 16-20, four times daily. Data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC.), with individual steer within period serving as the experimental unit. No interaction between corn silage hybrid and kernel processing were observed (P > 0.14). Corn silage treatment affected OM digestibility, with cattle fed bm3-EXP having greater OM digestibility than CON (P = 0.03), and both did not differ from bm3 (P > 0.17). Feeding bm3 and bm3-EXP corn silage did not have different (P = 0.17) NDF digestibility (54.4 and 58.2%, respectively), but both were greater (P < 0.01) than CON (45.5%). Digestibility of ADF did not differ from NDF with greater digestion for both brown midrib corn silages over the CON (P < 0.05). Total GE intake (Mcal/day) was greatest for bm3 corn silage (P < 0.07) as compared to CON and bm3-EXP, which did not differ (P = 0.94). Digestible energy (Mcal/day) was greater for bm3 over CON (P = 0.02) and bm3-EXP was intermediate between the two (P > 0.20). Digestible energy per unit of intake (Mcal/kg) was lowest (P < 0.03) for CON (3.09 Mcal/kg), with no difference (P = 0.24) between bm3 (3.25 Mcal/kg) and bm3-EXP (3.33 Mcal/kg). The use of kernel processing did not affect any digestibility parameters (P > 0.11) or measured DE. The use of brown midrib corn silage hybrids improved fiber digestibility and energy content of finishing diets at 40% inclusion.