Effects of whole or rolled corn and 20 or 40 percent grass hay levels on finishing performance of yearling steers

Abstract Text: A 141 d finishing study using 108 crossbred yearling steers (Initial BW = 415 ± 1.13 kg) evaluated whole (WC, 5.5 mm) or dry-rolled (RC, 2.8 mm) corn in diets with 20 or 40% grass hay (GH).  The study was a 2 x 2 factorial, with WC or RC as one factor and 20 or 40% GH as another.  Steers were stratified by BW and randomly assigned to pen (n = 12) and 1 of 4 treatments (n = 3 pens/treatment).  Diets were formulated to meet or exceed NRC recommendations and included modified corn distillers grains (25% DM basis) and an ionophore/vitamin/mineral supplement (2%, DM basis).  Initial BW were recorded on d 0 and every 28 d till harvest.  No corn type x forage level interactions were detected (P ≥ 0.21).  Initial BW were similar (P = 0.96) among treatments, and for WC and RC (P ≥ 0.47) across all five weight periods (WP).  Overall ADG was similar (P ≥ 0.25) across all WP, except d 56, steers on RC gained more compared to WC (P = 0.03).  Overall DMI was similar for WC and RC (P ≥ 0.42).  While overall G:F tended (P = 0.09) to favor RC, all interim periods had similar (P ≥ 0.29) G:F with the exception of d 56, when RC was lower than WC (P = 0.003).  Carcass attributes were similar (P ≥ 0.11) for WC and RC.  BW was similar (P ≥ 0.69) among GH treatments, at d 0 and through d 56; however greater (P ≤ 0.03) for 20 % GH at each subsequent period after d 56.  ADG was greatest for 20% GH during periods 1-3 and overall.  While DMI was similar (P ≥ 0.20) among GH treatments across all periods and for the whole 141 d trial.  G:F followed a similar pattern to ADG. The 20% GH cattle used less feed to gain a kg of body weight for periods 1-3 and overall, compared with 40 % GH (P ≤ 0.03).  Marbling score, LM area, BF and DP were similar among GH levels (P ≥ 0.16).  HCW and YG tended (P = 0.06) to be greater for 20% GH. Results indicate corn type and GH level did not interact and feeding RC slightly improved feed efficiency over WC.  20% GH diets had higher calculated energy values which did translate into improved ADG and feed efficiency over the 40% GH diets.

Keywords: Corn, Forage Level, Beef Cattle