156. Influence of Accelerated Feedlot Diet Adaptation, with or without a Calcareous Algae Rumen Buffer Additive, on Growth Performance, Liver Abscess Prevalence, and Carcass Traits of Beef × Dairy Steers.

Abstract The objectives of this study were to compare the influence of an accelerated feedlot adaptation strategy to a conventional approach and to evaluate the inclusion of a calcareous algae rumen buffer additive within an accelerated adaptation strategy on growth performance, liver abscess prevalence, and carcass characteristics of beef × dairy steers. A total of 157 steers (initial shrunk body weight (SBW) = 215.7 ± 20.8 kg) were received at the CSU research feedlot (Fort Collins, CO), rested for a minimum of 72 hours, and given access to a hay-based diet before processing. Steers were blocked by SBW and allocated to 21 pens. Pens were randomly assigned to one of three treatments: 1) a conventional 28-day adaptation period with 14 days on a 27% roughage (DM basis) starter diet followed by 14 days on an 18% roughage transition diet (CONV); 2) an accelerated 14-day adaptation period on an 18% roughage transition diet (ACON); or 3) an accelerated 14-day adaptation period on an 18% roughage transition diet with inclusion of a calcareous algae rumen buffer (Calmin; Feedworks USA, ltd.) supplied at 50 g/hd daily for the first 28 days on feed (DOF) and 25 g/hd for an additional 7 days (AADD). Individual SBW was collected on d14 and d28, and every 42 days thereafter throughout the 257-day feeding period. Pen was the experimental unit (n = 7). Data were analyzed using linear mixed-effects models with orthogonal contrasts to evaluate adaptation length (CONV vs. Accelerated [ACC; mean of ACON and AADD]) and additive treatment (AADD vs. ACON). Steers in the CONV treatment exhibited greater (P ≤ 0.02) average daily gain (ADG) and SBW at 28 DOF compared to ACC steers. Additionally, CONV steers tended (P = 0.10) to have greater overall ADG. The ACC steers had greater (P = 0.05) dry matter intake (DMI) from day 28 to 257 and tended (P = 0.07) to have greater DMI overall but were less (P ≤ 0.02) feed efficient than CONV steers. Final SBW and hot carcass weight also tended (P ≤ 0.09) to be greater in CONV compared to ACC. Feedlot growth performance and carcass traits were similar (P ≥ 0.13) for AADD steers compared to ACON. Overall liver abscess prevalence did not differ (P ≥ 0.36) among treatments. However, severe liver abscess incidence (A+, adhered, open, open and adhered) tended (P = 0.06) to be reduced by 81% in AADD compared to ACON. Accelerated diet adaptation hindered early growth and had lasting negative implications for feedlot performance compared to a conventional approach, while inclusion of a calcareous rumen buffer product in an accelerated strategy tended to reduce severe liver abscess prevalence but did not alter growth performance of beef × dairy steers.