Effect of processing method of hybrid rye grain on growth performance, dietary net energy utilization, and carcass characteristics of yearling beef steers fed a finishing diet.

This experiment evaluated the effects of replacing one-third of corn grain in a finishing diet with rye grain (RG) processed using one of three processing methods. Predominately Angus steers (n = 192, initial shrunk BW = 410 ± 20.9 kg) were blocked by source and pen location and assigned to one of four dietary treatments: dry-rolled corn (DRC), unprocessed RG (UNP), dry-rolled RG (DRR) and hammer-milled RG (HMR). Steers were fed for a total of 147 d. Pen was the experimental unit (6 pens per treatment, 8 steers per pen), and data were analyzed as a randomized complete block design using three contrasts: grain type [DRC vs. (UNP + DRR + HMR)], RG processing (UNP vs (DRR + HMR), and RG processing method (DRR vs HMR). Processing RG increased (P = 0.02) apparent neutral detergent fiber digestibility (aNDFD). Dry-rolling RG increased digestibility of dry matter and organic matter (P ≤ 0.02) and tended (P = 0.09) to increase starch digestibility compared to HMR. Dry matter intake (DMI) was unaffected by grain type (P = 0.55) and whether RG was processed (P = 0.27), but processing method affected DMI (P < 0.01; 11.5 and 12.3 kg/d for DRR and HMR, respectively). Grain type did not affect (P = 0.18) gain to feed (G:F). Rye processing tended to increase G:F by 4.4% (P = 0.08), and DRR steers tended to be 4% more efficient than HMR steers (P = 0.10; 0.146 and 0.140, respectively). Observed Net Energy for gain (paNEg) tended to be 3% greater for DRC than steers fed RG (P = 0.09) with RG processing having no effect (P = 0.17). Steers fed DRR tended to have 4.5% greater paNEg than HMR steers (P = 0.06; 1.32 and 1.26 Mcal/kg, for DRR and HMR, respectively). Rye grain processing tended to decrease dressing percentage (P = 0.07) but no other effects on carcass characteristics or USDA grade distributions were observed (P ≥ 0.24). Liver abscess prevalence was unaffected by grain type (P = 0.81) and whether RG was processed (P = 0.77). However, processing method tended (P = 0.08) to influence liver abscess prevalence (78.4% and 91.8% normal livers for DRR and HMR, respectively). Rye grain effectively replaced one-third of DRC in a finishing diet with minor effects on performance or feed efficiency. Processing RG tended to improve efficiency, and using dry-rolling tended to improve feed efficiency compared to hammer-milling under the conditions of this experiment.