Effect of length of time spent on the receiving diet on growth performance, rumination activity, and carcass outcomes in beef × dairy steers

We investigated the effect of increasing length of time spent on a 30% roughage equivalent (RE) receiving diet on growth performance, carcass characteristics, rumination activity, and serum metabolites in Angus × Holstein steers. Angus × Holstein steers (n = 144) were allotted by BW 18 pens (n = 8 steers/pen) in a randomized complete block design. A corn silage-based receiving diet, formulated to provide 30% roughage equivalency (RE; 60% DM basis) was fed for either 28 (REC28), 56 (REC56), or 84 d (REC84) post-feedlot arrival followed by a 12% RE finishing diet (6 replicate pens per treatment). Dry matter intake was reduced (P = 0.10) with increasing time spent on the receiving diet during the first 97 DOF. This reflected the reduced ADG and BW observed of the REC84 steers on d 97 (P < 0.01). No differences (P ≥ 0.18) were observed for post-receiving period ADG, DMI, and G:F. Less fat thickness (P = 0.07) was observed for REC84 steers, but no other differences (P ≥ 0.19) in carcass characteristics among treatments were noted. A numerical reduction in total liver abscessation was observed, driven by a numeric reduction (P = 0.13) in minor abscesses with increasing time spent on a 30% RE receiving diet. Increased time spent on the receiving ration was positively associated with rumination activity (P < 0.01). However, rumination activity (min/kg of NDF and peNDF consumed) decreased (P ≤ 0.02) with increasing time spent on the receiving diet. Dietary treatments did not affect (P ≥ 0.18) circulating concentrations of serum NEFA or glucose. Steers on the REC84 treatment exhibited the greatest concentration of circulating SUN (12.76 mg/dL), followed by steers on the REC28 treatment (12.41 mg/dL), and steers on the REC56 treatment had the least concentration of circulating SUN (11.49 mg/dL). Greater time spent on the receiving ration resulted in reduced DMI, ADG, and BW during the first 97 d, but did not alter overall feeding performance or carcass characteristics, including prevalence of liver abscesses. Increased time spent on the receiving diet positively influenced absolute rumination activity and minimally affected circulating concentrations of serum metabolites.