Impact of health management, health treatments, and zilpaterol hydrochloride supplementation on carcass quality, color, and palatability traits in heifers.

Two hundred sixty-eight strip loins were collected from heifers fed at Oklahoma State University in Stillwater, OK. In Exp. 1, heifers (n = 127) were assigned to 1 of 3 health management treatment groups: antimicrobial administrations were given based on standard feedlot protocol (SFP) or ruminal temperature (RT) or given a metaphylactic treatment of tulathromycin (MT) followed by visual assessment (VA). In Exp. 2, heifers (n = 155) were assigned to the same treatment groups as above and were supplemented zilpaterol hydrochloride (ZH) or control (CON). Three steaks were collected from each strip loin, 1 each for retail display, sensory evaluation, and Warner-Bratzler shear force (WBSF). Color was evaluated from the retail display steak using a trained color panel and objectively using a HunterLab Miniscan XE. An Instron Universal Testing Machine with a Warner-Bratzler head was used for evaluation of instrumental tenderness, and a trained sensory panel was used to assess palatability traits. Heifers treated by VA had the least number of antimicrobial administrations and lowest yield grade and also had the lightest HCW (P < 0.05) compared with the heifers treated by the other health management protocols. There were no subjective color attribute differences or sensory panel differences (P > 0.05) across all health management systems or antimicrobial administrations. There were no differences in carcass and performance traits for any antimicrobial administrations treatment groups (P > 0.05). Heifers who had 0 or 1 antimicrobial administrations had lower (P < 0.05) a* (redness/greenness: positive values = red and negative values = green), and b* (yellowness/blueness: positive values = yellow and negative values = blue) values compared with those who had 2 antimicrobial administrations. In Exp. 2, heifers treated by VA had the least number (P < 0.05) of antimicrobial administrations when compared with MT and RT. Health management group did not have any other effects on carcass, sensory, or color attributes. Zilpaterol hydrochloride supplementation caused a decrease (P < 0.05) in internal fat and yield grade, but no interactions were observed between the number of antimicrobial administrations and ZH supplementation. With the supplementation of ZH, WBSF significantly increased (P < 0.05). At the end of retail display, the control group had a greater (P < 0.05) surface discoloration when compared with the ZH group. Treatment and detection of bovine respiratory diseases (BRD) is critical to the industry economically and results from this study show that different methods can be used to detect BRD without dramatically impacting carcass, sensory, and retail case life characteristics.