229 The effects of direct-fed microbial with and without monensin plus tylan on performance, feed efficiency and feeding behavior patterns in feedlot steers

Abstract

Abstract Objectives of this study were to evaluate the effects of DFM with and without Monensin plus Tylan on feed efficiency and feeding behavior patterns in steers. Crossbred steers (n = 125; BW = 303 kg) were randomly assigned to 1 of 4 treatments in a 2 x 2 factorial design: (1) control (no feed additives), (2) DFM only (25 g/d; Natur’s Way), (3) Monensin (40 g/ton) plus Tylan only (MON) and (4) DFM and MON. In pens with GrowSafe feedbunks, steers were fed the grower diet for 14 d and transitioned to a finisher diet on 16 d. During the grower/transition phase, MON-fed steers had 9.5% higher (P < 0.05) ADG and improved F:G (7.8 vs 8.94; P = 0.06) and RFI (-0.28 vs 0.27 kg/d; P < 0.01) vs CON-fed steers. DFM-fed steers had lower (P < 0.01) ADG, but similar F:G and RFI than CON-fed steers. Daily variances of bunk-visit event frequencies were reduced (P < 0.01) in MON- vs CON-fed steers. During the finisher period, MON x DFM interactions (P < 0.10) were observed for ADG and F:G. MON-fed steers had numerically improved F:G (5%) when DFM was excluded, but not when DFM was included. MON-fed steers had lower RFI (P < 0.01; -0.23 vs 0.23 kg/d), whereas DFM-fed steers had higher RFI (P < 0.01) compared to respective controls. MON-fed steers ate less (P < 0.01) DMI, spent 9% more (P < 0.05) time consuming meals and had 14% slower (P < 0.01) meal eating rate then CON-fed steers. The DFM did not positively affect feed efficiency. Although the magnitude of improvement in feed efficiency due to MON was small, results demonstrated that MON may minimize digestive upsets by reducing daily variation in feeding behavior during diet transition and slow meal-eating rate on high-grain diets.