Effects of a phytogenic feed additive on growth performance, feed intake, and carcass traits of beef steers

Objective

This study examined the effects of a commercial phytogenic feed additive (PFA) on growth performance, feed efficiency, carcass traits, liver abscesses, and the immune response of growing and finishing steers.

Materials and Methods

Forty-five crossbred Angus steers (initial BW = 272 ± 20.5 kg) housed in individual pens (4.9 × 1.8 m) were used in a randomized complete block design in a 110-d growing and 120-d finishing experiment. Steers were blocked by BW and allocated to 1 of 3 treatments: control (without PFA and monensin), PFA at 500 mg/steer daily, or monensin at 300 mg/steer daily. Steers were fed a TMR ad libitum once daily and weighed on d 32, 59, and 110 in the growing phase but only at the beginning and the end of the finishing phase.

Results and Discussion

During growing, DMI did not differ, whereas final BW (trend; 415 vs. 403 kg) and ADG (numerically; 1.31 vs. 1.20 kg/d) were greater with PFA than control but did not differ from monensin (BW = 422 kg and ADG = 1.38 kg/d). Gain:feed was greater with monensin (0.173) than with PFA (0.161) and for the control (0.156). During finishing, ADG, G:F, and carcass traits did not differ, whereas DMI and acute proteins were lesser with monensin than with PFA and for the control.

Implications and Applications

Growing steers fed PFA had similar DMI and ADG but lesser G:F than did those given monensin. Both PFA and monensin resulted in similar growth performance and G:F in the finishing phase.