159 Impact of Constant Inclusion or Decreasing Inclusion of Distillers Grains with High-Quality or low-Quality Roughage on Finishing Cattle Performance

Abstract

Abstract Crossbred, calf-fed steers (n = 480; initial body weight = 292 ± 19 kg) were used in a randomized block design finishing experiment with a 2 × 3 arrangement of treatments to evaluate the impact of constant inclusion or decreasing inclusion of modified distillers grains plus solubles (MDGS) with high-quality or low-quality roughage on finishing cattle performance. Dietary treatments included two roughage sources to provide similar neutral detergent fiber (NDF) from forage (6% corn stalks versus 12% corn silage DM basis) in three diets containing 0, 15, or decreasing inclusion of distillers (30, 15, then 0% across the feeding period). A total of 48 (10 steers/pen) pens were used with 8 pens/treatment. There was an interaction (P = 0.04) between roughage source and MDGS inclusion for dry matter intake (DMI). Cattle fed stalks with decreasing inclusions of MDGS (30-0%) had greater DMI than those fed silage as roughage source, but at 0% inclusion of MDGS there was no difference between roughage sources. No other significant interactions were observed, so main effects will be presented. Cattle fed the diet with 0% MDGS inclusion had reduced (P < 0.05) hot carcass weight (HCW), DMI, average daily gain (ADG), and 12th rib fat, and poorer G:F compared with cattle fed diets where MDGS was at 15% inclusion continuously or when MDGS decreased from 30% to 0%. For the treatment where MDGS was decreased from 30% to 0%, performance differed from that of cattle fed 15% distillers continuously. Cattle fed decreasing inclusions of MDGS (30-0%) had less (P < 0.01) DMI, ADG and tended (P = 0.07) to have lighter HCW. But G:F was not (P = 0.25) affected compared with when distillers was fed at 15% continuously. Marbling score was impacted by distillers inclusion (P = 0.03), where cattle fed 15% MDGS had greater (P = 0.01) marbling score than 0% inclusion and tended (P = 0.06) to be greater than cattle fed 30-0% MDGS. Even though there are differences in marbling score across treatments, all three treatments were within the choice grade and reflect ADG differences across treatments. Cattle fed silage consumed less, gained the same, and had greater G:F (P < 0.01). Based on numerically less HCW, ADG, and poorer G:F, these data suggest that feeding 6% corn stalks did not produce similar performance as feeding 12% corn silage. These data suggest that feeding 15% distillers was not enough to offset decreased quality roughage (stalks) compared with silage as roughage which contradicts previous studies when 30% distillers were fed.