155 Effect of Forage Inclusion Strategy on Finishing Beef Cattle Performance and Liver Abscesses

Abstract

Abstract This study evaluated different strategies of forage inclusion for finishing beef cattle and their impact on performance, carcass quality, and liver abscesses. Steers (n=360, 400±29 kg) were blocked by weight and randomly assigned to one of four treatments (15 steers/pen, 6 pens/treatment) in a complete randomized experiment. Treatments were: 1) positive control (+CON) fed a diet (7.5% forage on a diet DM basis) with tylosin (11 mg/kg); 2) negative control (–CON; 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), the inverse of the DECR without tylosin. There were no differences in initial BW, DMI, and G:F (P≥0.38). The INCR steers had lower ADG (1.63 vs. 1.74 kg, P=0.05), total BW gain (287 vs. 306 kg, P=0.05), and tended to have lower final BW and carcass weight (P=0.07) compared to +CON, with no differences from the other treatments. No differences were observed for carcass dressing percentage, ribeye area, marbling scores, and quality grades (P≥0.41). Backfat thickness and yield score were lower for INCR steers (14.2 mm and 3.42) compared to –CON (16.9 mm and 3.82, P=0.04), while other treatments did not differ. There was no difference for the percentage of steers with liver abscess or severe abscess (A+; P≥0.17). However, the percentage of steers with minor liver abscesses (A) was numerically less for +CON (51.8%) and DECR (51.8%) compared to –CON (62.2%) and INCR (64.3%, P=0.055). This suggests that higher dietary concentrations of forage in the beginning stages of finishing, with a subsequent decline thereafter has the potential to decrease the proportion of minor liver abscesses, similar to the inclusion of tylosin in a high-grain diet, without impacting growth performance or carcass quality.