Abstract
This study compared the yield of barley and hybrid rye when harvested for silage, and evaluated the effects of replacing barley silage (BARS) with hybrid rye silage (HRS) on dry matter intake (DMI), growth, and carcass characteristics of feedlot steers. The whole-plant hybrid rye (late milk) and barley (soft dough) were each harvested from 3 replicate 7.85-ha plots in 2022 and 2023 and ensiled (n = 3/treatment/yr). In each year, 192 steers were allocated to 1 of 16 pens in a completely randomized block design for growing (4 pens/treatment/yr) and finishing (5 or 6 pens/treatment/yr) phases. Treatments during the growing phase (84 d) included a control diet (GCON) that contained 60% BARS, and in the remaining treatments HRS replaced 33 (GLOW), 67 (GMED), or 100% (GHIGH) of the BARS (DM basis). Steers were then re-randomized and allocated to 1 of 16 pens for the finishing phase with diets that contained (DM basis) 10% BARS (FCON) or diets where HRS replaced 50% (FMED) or 100% (FHIGH) of the BARS. Steers were fed for 112 d. Forage DM yield did not differ between whole plant hybrid rye and barley (3.96 vs. 3.70 mT/ha). During the growing phase, increasing the HRS inclusion at the expense of BARS decreased DMI (quadratic, P = 0.02), average daily gain (ADG; quadratic, P < 0.01), and final BW (quadratic, P = 0.02) with the magnitude of the response increasing with increasing HRS inclusion. In addition, the gain:feed (G:F) ratio linearly decreased (P < 0.01) with increasing HRS inclusion. During finishing, DMI tended to linearly decrease (P = 0.06), ADG decreased and then increased (quadratic, P = 0.04) with the lowest ADG observed for FMED, while G:F was unaffected. Carcass weight for steers fed FMED and FHIGH did not differ but were lighter (quadratic, P = 0.02) than FCON, and dressing percentage decreased linearly from 58.81 to 58.34% (P = 0.03) as HRS inclusion increased. Carcass yield grade and marbling were unaffected. Increasing HRS inclusion at the expense of BARS linearly decreased the proportion of steers with minor (P = 0.02) and severe (P = 0.04) liver abscesses. In conclusion, while forage yield may not differ between hybrid rye and barley, increasing the inclusion rate of HRS in diets for growing steers reduced DMI and ADG. During finishing, increasing the inclusion of HRS may decrease DMI and resulted in lighter hot carcass weight without affecting carcass yield grade or marbling.