High-Fibre High-Lipid By-Product Pellets Are an Effective Replacement for Barley Grain in Diets for Finishing Beef Cattle

This study was conducted to evaluate the effects of treating oat hulls with CaO prior to inclusion in a high-lipid by-product pellet (HLP) on DMI, ruminal fermentation, and total tract digestibility (Study 1) and growth performance (Study 2). In Study 1, 6 ruminally cannulated cross-bred Hereford heifers (374 kg ± 18 kg BW) were used in a replicated 3 3 Latin square design. Periods consisted of 25 d, with the last 5 d used for sample collection. Dietary treatments included a barley-based control diet (CON) composed of 90% concentrate: 10% barley silage. The barley grain and canola meal in the CON were replaced with HLP (30% DM basis) that were not treated (HLP-NT) or a treatment where pelleted oat hulls were treated with 7.5% CaO (HLP-CaO). Study 2 used 210 steers assigned to 21 pens in a 113-d finishing study to evaluate DMI, ADG, and gain:feed (G:F). Steers were fed diets similar to Study 1. Data from Study 1 were analyzed with the mixed model of SAS including the fixed effects of treatment, period, and square, and the random effect of heifer nested in square. Data from Study 2 included treatment as a fixed effect. For Study 1, DMI and ruminal short-chain fatty acid concentration were not affected. For individual short-chain fatty acids, the molar proportion of isobutyrate was greatest (P ≤ 0.018) for HLP-NT, intermediate but not different for CON, and least for HLP-CaO. Ruminal pH was not affected (P > 0.10). Apparent total-tract digestibility of DM (P < 0.05) and OM (P < 0.001) was greatest for the CON (70.7, 79.0%) compared to HLP-NT (68.9, 66.3%), and HLP-CaO (68.4, 65.4%). Digestibility of CP was greater (P = 0.02) for the HLP-NT (65.7%) compared to the CON (64.0%), but was not different from HLP-CaO (65.7%). Ether extract digestibility was greater for the HLP-NT (82.6%) and HLP-CaO (79.1%) treatments compared to CON (85.5%; P < 0.01). In Study 2, starting BW (424 kg), ending BW (645 kg), and ADG (2.0 kg/d) were not different. However, DMI (kg/d) was greater (P < 0.01) for HLP-CaO (12.5) and HLP-NT (12.6) than CON (11.5), and G:F tended to be reduced (P = 0.08; 0.15, 0.15, and 0.16 kg/kg, respectively). Calcium oxide treatment of oat hulls did not improve digestibility, but the inclusion of HLP is an effective partial replacement of barley grain without negatively affecting ruminal fermentation, and ADG.