Assessment of forage inclusion strategies as a means of reducing liver abscesses in finishing feedlot cattle*†

This study evaluated different strategies of forage inclusion in finishing beef cattle diets and their ef- fects on feed intake, ruminal fermentation and microbiota, blood serum parameters, growth performance, carcass quality, and liver abscesses. Steers (n = 360, 400 ± 29 kg) were stratified by weight and randomly allocated across 24 pens, which were randomly assigned to 1 of 4 dietary treatments (15 steers/pen, 6 pens/treatment) in a completely randomized experiment. Treatments included: (1) positive control (+CTRL) fed a diet (7.5% forage on a diet DM basis) with tylosin (11 mg/kg); (2) negative control (−CTRL; control diet without tylosin); (3) a diet where forage concentration decreased (DECR) every 42 d and was static for the last 84 d (forage represented 15%, 9%, 3%, and 3% of DM, respectively) without tylosin; and (4) a diet where forage concentration increased (INCR), inverse of the DECR without tylosin. The +CTRL steers had greater ADG (1.74 kg/d vs. 1.63 kg/d), shrunk total BW gain (306 vs. 287 kg), and a tendency for greater final BW (705 vs. 687 kg), than than INCR steers. As expected, a diet × period interaction was observed for DMI, but it did not differ among treatments over the full study. Yield scores and rib fat thickness were greater in –CTRL than INCR steers. The percentage of steers with minor liver abscesses tended to be less for +CTRL (51.8%) and DECR (51.8%) compared with −CTRL (62.2%) and INCR (64.3%). Greater dietary con- centrations of forage earlier in the finishing phase, with a subsequent decline thereafter, has the potential to de- crease the proportion of minor liver abscesses similar to typical finishing diets including tylosin, without affecting growth performance or carcass quality.