Barley Silage or Corn Silage Fed in Combination with Barley Grain, Corn Grain, or a Blend of Corn and Barley Grain for Finishing Beef Cattle

Abstract

The objectives of the current studies were to evaluate the effects of silage (S) and cereal grain (G) source and their interaction (S × G) on growth performance, digestibility, and carcass characteristics (Study 1) and dry matter intake, ruminal fermentation, total-tract digestibility, and nitrogen balance (Study 2) for finishing beef cattle. For Study 1, 288 steers weighing 465 ± 28 kg were randomly assigned to 1 of 24 pens (12 steers/pen) in an 89-d finishing study. Study 2 used five ruminally cannulated heifers in an incomplete 6 × 6 Latin square design. Periods were 25-d in duration with 5 d of diet transition, 13 d of dietary adaptation, and 7 d of sample collection. Dietary treatments for both studies included corn silage (CS) or barley silage (BS) at 8% of DM. Within each silage source, diets contained dry-rolled barley grain (BG; 86% of DM), dry-rolled corn grain (CG; 85% of DM), or an equal blend of barley and corn grain (BCG; 85% of DM). In Study 1, there were no interactions between silage and cereal grain source (P ≥ 0.10). Feeding CG increased (G, P < 0.01) DMI by 0.8 and 0.6 kg/d relative to BG and BCG, respectively. Gain-to-feed was greater (G, P = 0.04) for BG (0.17 kg/kg) than CG (0.16 kg/kg), but not different from BCG (0.17 kg/kg). Furthermore, average daily gain (2.07 kg/d) and final body weight were not different among treatments (P > 0.05). Hot carcass weight was 6.2 kg greater (372.2 vs. 366.0 kg; S, P < 0.01) and dressing percent was 0.57% greater (59.53 vs. 58.96 %; S, P = 0.04) for steers fed CS than BS, respectively. In Study 2, DM intake and mean pH were not affected by diet. Total SCFA concentrations were greater for BCG than BG or CG (G, P < 0.01) and for CS (S, P < 0.01) relative to BS. Molar proportion of acetate was increased for BS-BG and BS-CG (S × G, P < 0.01), while molar proportion of propionate was greatest for CS-BG (S × G, P < 0.01). Rumen ammonia-nitrogen concentrations were greatest for CG (G, P < 0.001), and higher for CS than BS (S, P = 0.02). Apparent total-tract digestibility of DM, OM, aNDFom, starch and gross energy were greatest for BG (G, P ≤ 0.04). Dietary digestible energy content (Mcal/kg) was greatest for BG treatments (G, P = 0.03). Total nitrogen retention (g/d and % of intake) was greatest for CS-BG (S × G, P ≤ 0.03). The potentially degradable fraction of DM, CP, and starch were greater for CG (P ≤ 0.03) than BG. For silage sources, CS had greater 24, 48 and 72-h starch digestibility (P ≤ 0.03) relative to BS. These results indicate that feeding dry-rolled BG may improve performance and digestibility when compared to CG and BCG and CS may provide benefits over BS. Improvements related to feeding BG and CS may be due to greater propionate production, improved nutrient digestibility, and greater N retention.