The objective of this study was to evaluate processing methods for frozen beef subprimals; the effects of freezing and thawing rates on tenderness, sensory properties, and retail display were evaluated. There were 6 treatments: fresh, never frozen 14 d wet aged (14D); fresh, never frozen 21 d wet aged (21D); blast frozen-fast thawed (BF); blast frozen-slow thawed (BS); conventionally frozen-fast thawed (CF); and conventionally frozen-slow thawed (CS). All frozen beef subprimals were aged for 14 d before freezing. Three beef subprimal cuts, rib eye roll (n=90), strip loin (n=90), and top sirloin butt (n=90), were used with 3 replications of 5 samples per treatment per week (total of 9 wk, n=270). Blast freezing occurred by placing spacers between the boxes of meat on pallets at -28°C with high air velocity for 3 to 5 d. Conventional freezing occurred with boxes of meat stacked on pallets and placed in a -28°C freezer with minimal air movement for at least 10 d. Fast thawing of subprimals (to an internal temperature of -1°C to 1°C) occurred by immersion in a circulating water bath (<12°C) for 21 h, and slow thawing of subprimals occurred over a 2-wk period by placing individual subprimals on tables at 0°C. Steaks (2.5 cm thick) were cut from the longissimus thoracis (LT), longissimus lumborum (LL), and gluteus medius (GM) for Warner-Bratzler shear force (WBS), trained sensory evaluation, and retail display. For LL and GM beef steaks, frozen treatments were equal or lower in WBS values to 14D and 21D beef steaks. No differences were detected in WBS among the treatments applied to GM beef steaks (P=0.08). There were no differences in sensory tenderness among the LL, LT, and GM (P>0.05). All LL and LT beef steaks had approximately 4 d to 40% discoloration, and all GM steaks had over 3 d to 40% discoloration. Steaks from the LL and LT began to discolor at about 3 d, and the GM began to discolor after 1 d. For all beef subprimals, purge loss during storage and thawing was significantly greater for the slow-thawed subprimals (P<0.01), and all fast-thawed subprimals were equal or superior to 14D and 21D (P<0.01) in storage and thawing purge. During retail display, the greatest purge loss occurred in fast-thawed treatments (P<0.01). Overall, freezing rate did not affect purge loss, and neither freezing nor thawing rates had significant meaningful effects on WBS, and sensory properties were comparable with fresh, never-frozen subprimals.

The study objective was to determine the effects of Bacillus subtilis PB6 and/or chromium propionate supplementation on health, growth performance, and carcass characteristics of high-risk beef cattle during a 56-d feedlot receiving period and the subsequent finishing period. Four truckload blocks of crossbred beef bulls (n=300) and steers (n=84; BW = 220 ± 16.2 kg) were sourced from regional auction markets and assigned randomly to treatments arranged in a 2 × 2 factorial. The generalized complete block design consisted of 12 pen replications per treatment with pen as the experimental unit. Treatments were: 1) placebo control (CON); 2) 13 g/animal daily of B. subtilis PB6 (CST); 3) 450 ppb DM chromium propionate (CHR); and 4) 13 g/animal daily of B. subtilis PB6 and 450 ppb DM chromium propionate (CST+CHR). Treatments were top dressed in feed bunks daily using 0.45 kg/animal ground corn carrier immediately following feed delivery. Data were analyzed using mixed models. During the receiving period, DMI increased (P ≤ 0.03) for CST during each interim period. Overall receiving period daily DMI was 0.35 kg/animal greater for CST (P = 0.01). Cattle fed CST had greater (P ≤ 0.06) BW on days 14, 28, and 56. Likewise, ADG was improved for CST from day 0 to 14 (P = 0.04) and for the overall receiving period (day 0 to 56; P = 0.04). From days 0 to 14, CST tended (P = 0.08) to increase G:F. During the finishing period, CHR reduced (P = 0.02) final BW and ADG (day 56 to final; P = 0.01) and ADG was less for CHR over the entire feeding period (day 0 to final; P = 0.03). Main effect of both CST (P = 0.02) and CHR (P = 0.03) decreased the overall treatment rate for bovine respiratory disease (BRD), and CST reduced overall antimicrobial treatment cost by $3.50 per animal compared to CON (P = 0.03). Hot carcass weight decreased (P = 0.01) in cattle fed CHR. Percentage of edible livers tended to increase (CST × CHR; P = 0.08) in the CST treatment. Feed intake and growth performance outcomes during the receiving period were improved by CST but not CHR supplementation. However, both CST and CHR supplementation decreased BRD morbidity rate. During the finishing period, performance and HCW were reduced in cattle supplemented with CHR.

Feeding zilpaterol hydrochloride (ZH) with ruminally protected AA was evaluated in a small-pen feeding trial. Crossbred steers ( = 180; initial BW = 366 kg) were blocked by weight and then randomly assigned to treatments (45 pens; 9 pens/treatment). Treatment groups consisted of no ZH and no AA (Cont-), ZH and no AA (Cont+), ZH and a ruminally protected lysine supplement (Lys), ZH and a ruminally protected methionine supplement (Met), and ZH and ruminally protected lysine and methionine (Lys+Met). Zilpaterol hydrochloride (8.3 mg/kg DM) was fed for the last 20 d of the finishing period with a 3-d withdrawal period. Lysine and Met were top dressed daily for the 134-d feeding trial to provide 12 or 4 g·hd·d, respectively, to the small intestine. Carcass characteristics, striploins, and prerigor muscle samples were collected following harvest at a commercial facility. Steaks from each steer were aged for 7, 14, 21, and 28 d, and Warner-Bratzler shear force (WBSF) was determined as an indicator of tenderness. Prerigor muscle samples were used for immunohistological analysis. Cattle treated with Met and Lys+Met had increased final BW ( < 0.3) and ADG ( < 0.05) compared to Cont- and Cont+. Supplementation of Lys, Met, and Lys+Met improved G:F ( < 0.05) compared to Cont- during the ZH feeding period (d 111 to 134) as well as the entire feeding period ( < 0.05). Zilpaterol hydrochloride increased carcass ADG ( < 0.05) when compared to non-ZH-fed steers. Methionine and Lys+Met treatments had heavier HCW ( < 0.02) than that of Cont-. Yield grade was decreased ( < 0.04) for Cont+ steers compared to steers treated with Lys, Lys+Met, and Cont-. Tenderness was reduced ( < 0.05) with ZH regardless of AA supplementation. Lysine, Met, Lys+Met, and Cont+ had less tender steaks ( < 0.05) throughout all aging groups compared to Cont-. Steaks from Lys-treated steers were less tender ( < 0.05) than those of Cont+ during the 7- and 14-d aging periods. Nuclei density was the greatest with Cont- cattle compared to all other treatments suggesting a dilution effect of the nuclei in the larger muscle fibers with ZH feeding. Supplementation of Met in conjunction with ZH feeding increased ADG and HCW although this may lead to decreased tenderness even after aging for 28 d. These findings indicated that steers fed ZH may require additional AA absorbed from the small intestine to maximize performance.

The objectives of this experiment were to evaluate the effects of feeding Bacillus subtilis PB6 on clinical health, performance, and carcass characteristics of feedlot steers. Bos indicus crossbred steer calves [n = 397; 342 kg initial body weight (BW)] were randomly assigned to pens by initial BW; pens (n = 24) were randomly assigned to 1 of 2 of the following experimental treatments: 1) no supplemental dietary direct-fed microbial, control (CON; n = 12 pens); or 2) 13 g/steer daily B. subtilis PB6 (CLO; CLOSTAT ®, Kemin Industries, Des Moines, IA; n = 12 pens). Steers were housed in 12.2 × 30.5 m soil surfaced pens; pen served as the experimental unit. The percentage of cattle treated once or twice for bovine respiratory disease (BRD) did not differ among treatments (P ≥ 0.27); BRD mortality also did not differ between CON and CLO (P = 0.34). During the receiving period, final BW (P = 0.97), average daily gain (ADG; P = 0.91), dry matter intake (DMI; P = 0.77), and gain:feed (P = 0.79) were not different among treatments. There was a tendency (P = 0.09) for CLO supplemented steers to be 14% more efficient from d 0 to 14 of the receiving period. Final BW, overall finishing phase ADG, and DMI did not differ by treatment (P ≥ 0.14); ADG was 0.14 kg greater for CLO than CON (P = 0.03) from d 29 to 56 of the finishing period. Gain: feed tended (P = 0.07) to be 7% greater (0.144 vs 0.141) for CLO than CON throughout the duration of the finishing period, and 6.7% greater (P = 0.08; 0.152 for CLO vs. 0.150 for CON) for the entirety of the experiment. Carcass traits did not differ among treatments (P ≥ 0.31). The results of this experiment suggest that supplementing 13 g/steer daily B. subtilis PB6 may improve feed efficiency in feedlot cattle.

Providing cattle a more bioavailable zinc (Zn) source prior to administering a beta adrenergic agonist (βAA) may enhance the metabolic pool of primary nutrients that will influence the magnitude of the βAA response. Calf-fed Holstein steers were supplemented with a Zn methionine supplement (ZnMet; ZINPRO®; Zinpro Corporation, Eden Prairie, MN) for 115 ± 5 days prior to harvest along with zilpaterol hydrochloride (ZH; Zilmax®; Merck Animal Health, Summit, NJ) for the last 20 days with a 3-day withdrawal to evaluate the effects on growth and carcass performance together with gene and protein expression of skeletal muscle, adipose tissue, and fatty acid composition of polar and neutral lipid depots. Steers (n = 1296; initial weight = 468.5 ± 0.5 kg) were sorted by weight, blocked by harvest date, and randomly assigned to pens (n = 12) and treatments: control (90 ppm Zn from ZnSO4) and ZnMet (Control plus 720 mg Zn from ZnMet/hd/d). There were no differences (P > 0.05) in growth performance or carcass characteristics. The ZnMet-fed cattle had reduced (P < 0.05) abundance of myosin heavy chain (MHC)-IIX, β1-adrenergic receptor (βAR), peroxisome proliferator-activated receptor gamma, and stearoyl-CoA desaturase mRNA in skeletal muscle tissue. The ZnMet cattle had greater (P < 0.05) abundance of MHC-II protein, increased MHC-IIA and IIX cross-sectional areas (P < 0.05), an increased percentage of MHC-I fibers (P < 0.05), and a decreased percentage of MHC-IIX fibers (P < 0.05). The combination of ZnMet and ZH had positive biological effects on musculoskeletal tissue; however, these molecular effects were not significant enough to impact overall feedlot and carcass performance.