Effects of corn processing method and particle size on feedlot performance and carcass traits of yearling steers

Abstract Text:

The objective of this study was to evaluate the effects of corn processing and particle size on performance and carcass traits of steers fed finishing diets with decreasing forage levels.  One hundred and twenty black crossbred yearling steers (initial BW 406.80 ± 1.23 kg) were blocked by BW and randomly allotted to 12 pens (10 steers/pen).  The pens were assigned randomly to one of three corn processing treatments:  1) whole (WC), 2) dry rolled (RC), and 3) finely ground (GC).  Mean particle size for WC, RC, and GC was 5.49 ± 0.14 mm, 2.84 ± 0.12 mm, and 1.35 ± 0.16 mm, respectively.  Diets were similar in protein (≥ 13.4%) and energy (≥ 0.98 Mcal NEg/Kg), met or exceeded NRC nutrient requirements, and included modified distillers grains, grass hay, corn silage, Rumensin®, vitamins, and minerals.  Dietary forage levels for all treatments was 31.5 % initially (23% corn; DM basis) and decreased at 41 d intervals to 25.0 and 15.5% (35 and 53% corn, respectively), followed by a final level of 13.5% (55% corn) for the last 22 d.  Forage levels were defined as the sum of the hay and 50 % of the dietary corn silage.  Steers were weighed individually on d 0 and at each forage level decrease, over the 145 d trial.  All cattle were harvested on the same date at a commercial abattoir.  Carcass attributes evaluated after a 24-hour chill included: 12^th rib fat depth, LM area, KPH, marbling, and USDA Yield grade.  Performance and carcass characteristics were analyzed using the GLM procedure of SAS, with pen serving as the experimental unit.  Final BW and overall ADG were similar (P ≥ 0.21) for all treatments.  DMI was similar (P = 0.24) for RC and GC and greatest (P ≤ 0.01) for WC (13.56, 13.24, and 14.42 Kg/d, respectively).  Gain efficiency was lowest (P < 0.01) with WC (0.154) but similar (P > 0.05) between RC (0.169) and GC (0.166).  All carcass characteristics, except KPH, were similar (P ≥ 0.07) among treatments.  The percent KPH was similar (P > 0.05) for RC and GC but greater for WC (P = 0.01).  These results indicate processing corn by RC or GC, to maintain a particle size between 1.35 ± 0.16 mm and 2.84 ± 0.12 mm will result in improved DMI and gain efficiency for finishing yearling steers fed diets with decreasing forage levels.

Keywords: beef, corn, particle size