76 Effects of replacing monensin and tylosin in finishing cattle diets with essential oils and/or benzoic acid on growth performance and carcass characteristics

Abstract

Abstract This study examined the effects of replacing monensin and tylosin with essential oils and/or benzoic acid in finishing cattle diets on growth performance, feed efficiency, and carcass characteristics. Crossbred steers (n = 68; BW = 539 ± 4 kg) were blocked by starting weight into three blocks and were assigned to 1 of 5 finishing diets: no additional supplement (CON), monensin/tylosin (M/T), essential oils (EO), benzoic acid (BA), or a combination of essential oils and benzoic acid (COMBO). Steers were housed with two dietary treatments represented in seven pens, while an eighth pen only housed steers fed the CON diet. Individual animal feed intake was collected using an Insentec feeding system, so steer was the experimental unit for all analyses. Data were analyzed using a randomized complete block design with fixed effect of treatment and random effect of block. Final weight, average daily gain, and dry matter intake were similar (P > 0.12) among treatments. Gain to feed ratio differed (P = 0.05) among treatments, specifically steers fed the M/T diet had greater G:F compared with steers fed CON, EO, and COMBO diets. For carcass characteristics, there were no significant treatment differences in hot carcass weight (P = 0.19), dressing percentage (P = 0.62), ribeye area (P = 0.49), fat thickness (P = 0.84), calculated yield grade (P = 0.91), marbling score (P = 0.07), and yield grade (P = 0.43). Quality grade differed (P = 0.05) among treatments, with steers fed the EO diet having a lower quality grade than all other dietary treatments. Overall, steers supplemented with essential oils and(or) benzoic acid had similar gain, feed intake, and carcass parameters as steers fed CON, while steers fed M/T had slightly improved feed efficiency compared to all other treatments.