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.

Ruminal acidosis challenge impact on ruminal temperature in feedlot cattle.

The objective of this experiment was to determine if ruminal temperature rise coincides with pH reduction using an acidosis challenge model. Twelve ruminally cannulated steers (518 ± 28 kg BW) were administered ruminal temperature-monitoring devices that recorded temperature every 2 min. Steers were fed a 63% concentrate diet at 1.6% BW for 20 d before being randomly assigned to 1 of 3 acidosis challenge treatments: no dietary change (CON), one-half of daily DMI replaced with cracked corn (HALF), or all of daily DMI replaced with cracked corn (CORN). The challenge was initiated by ruminally dosing steers with their treatment diets. Ruminal pH and rectal temperatures (T(rec)) were recorded every 3 h for 72 h. All steers were offered CON diets at 24 and 48 h after challenge. Ruminal pH showed a treatment × day effect (P = 0.01). Ruminal pH of CORN steers was lower (P = 0.03) than that of HALF steers on d 1, was lower (P ≤ 0.004) than that of HALF and CON steers on d 2, and tended to be lower (P ≤ 0.10) than that of HALF and CON steers on d 3. Treatment did not affect (P ≥ 0.42) RecT. Ruminal temperature (T(rum)) showed a treatment · d(-1) · h(-1) after feeding interaction (P < 0.01). At 3 h after challenge, T(rum) of CORN and HALF steers was higher (P ≤ 0.01) than that of CON steers. On d 2, T(rum) of CORN steers was higher (P ≤ 0.03) than that of CON between 6 and 12 h after feeding. From 15 to 21 h after feeding on d 2, T(rum) of HALF steers was higher (P < 0.01) than that of CORN and CON steers. On d 3, at the time of feeding until 3 h later, T(rum) of CORN steers was lower (P ≤ 0.04) than that of all other steers. Rectal temperature was correlated (P ≤ 0.01) with T(rum) on all days for CON and CORN steers. Ruminal pH was negatively correlated (P ≤ 0.04) with T(rec) on d 2 and T(rum) on d 1 in CORN steers, and T(rum) was negatively correlated (P ≤ 0.02) with ruminal pH in HALF and CON steers on d 1 and 3, respectively. The amount of time above T(rum) of 39.0°C or 39.45°C was correlated (P ≤ 0.05) with the time spent below a ruminal pH of 5.5 in CORN steers; however, time above T(rum) of 39.0°C did not differ (P = 0.87) among treatments. Results indicate that there is a negative relationship between T(rum) and ruminal pH during an acidotic episode; therefore, T(rum) monitoring can detect a potential acidotic episode.

Vitamin E supplementation in beef finishing diets containing 35% wet distillers grains with solubles: feedlot performance and carcass characteristics.

Supplementation of vitamin E has indications for improving cattle health, performance, and retail characteristics when included in grain-based diets. This experiment was conducted to determine performance and carcass characteristics of steers fed diets containing wet distillers grains with solubles (WDGS) and supplemented with vitamin E. Steers of mixed Bos indicus and Bos taurus breeding (n = 199; BW = 363 ± 32 kg) were blocked by BW and assigned to 1 of 4 supplemental vitamin E (VITE) treatments [0 (control), 125, 250, and 500 IU·steer(-1)·d(-1)], which were fed for the last 97 d of the feeding period. Two blocks were on feed 129 d, and 3 blocks were fed for 150 d. Steers were fed a dry-rolled corn-based finishing diet with 35% WDGS (DM basis). Individual BW were measured initially, the initial day of vitamin E supplementation, and the day of slaughter. Carcass weights were collected at slaughter, and carcass data were collected after a 36-h chill. Body weight and ADG were not affected by VITE (P ≥ 0.34). There was a tendency for a linear (P = 0.08) increase in carcass-adjusted BW with increasing VITE. Use of carcass-adjusted final BW resulted in a linear increase (P = 0.04) in ADG with increasing VITE. Pre-vitamin E and vitamin E feeding period DMI were not affected (P ≥ 0.24) by VITE, but there was a tendency (P = 0.08) for a linear increase in overall DMI with increasing VITE. No difference (P ≥ 0.29) occurred in G:F measures using BW gains, but G:F using carcass-adjusted BW gains resulted in a trend (P = 0.11) for G:F to increase linearly with increasing VITE. Hot carcass weights tended (P = 0.08) to increase linearly with increasing dietary vitamin E. Vitamin E supplementation resulted in no effects (P ≥ 0.13) on measured carcass characteristics. Calculated yield grades (YG) were also not affected (P ≥ 0.37). However, the distribution of calculated YG resulted in a quadratic effect (P = 0.02) for YG 3 with the control and 500 VITE being greater than the 2 intermediate amounts. However, the percentage of carcasses grading YG 3 or less were not affected by vitamin E supplementation (P = 0.64). No differences were observed in the distribution of quality grades based on marbling scores (P ≥ 0.57). Data from this study suggest that vitamin E supplemented above basal requirements during the last 97 d of the feeding period in finishing diets containing 35% WDGS results in slight to no effect on animal performance or carcass characteristics.