Three experiments with factorial arrangements of treatments were designed to test the efficacy of avian-derived polyclonal antibody preparations (PAP) against Streptococcus bovis (PAP-Sb) or Fusobacterium necrophorum (PAP-Fn) in reducing ruminal counts of target bacteria in beef steers supplemented or not with feed additives (300 mg of monensin/d and 90 mg of tylosin/d; MT). Feeding increasing doses of PAP-Sb in Exp. 1 or a single dose in Exp. 2 reduced S. bovis counts in a cubic fashion (P = 0.014). In Exp. 1 and 2, inclusion of MT in the diet had no effect (P > 0.05) on ruminal S. bovis counts. In Exp. 2, ruminal pH was increased (P < 0.05) by feeding PAP-Sb, MT, and PAP-Sb plus MT. Ruminal F. necrophorum counts were reduced by feeding PAP-Fn (P = 0.002) and MT (P < 0.001). Reduction in ruminal F. necrophorum counts was greater (P = 0.008) when feeding MT alone than when feeding PAP-Fn and MT together. In Exp. 3, ruminal S. bovis counts were not affected (P = 0.64) by PAP-Fn. Ruminal pH was not affected (P = 0.61) by feeding PAP-Fn, and the total anaerobic bacterial count was not affected (P > 0.05) by either PAP-Sb or PAP-Fn in Exp. 1 or Exp. 3. In conclusion, PAP of avian origin and against S. bovis or F. necrophorum were effective in reducing target ruminal bacterial populations. These PAP could be effective in preventing the deleterious effects associated with these bacteria, and possibly in enhancing animal performance.

Two experiments were conducted to evaluate the influence of vaccination on the acute-phase protein (APP) reaction (Exp. 1 and 2) and measures of performance (Exp. 2) in growing beef calves. In Exp. 1, the APP reaction was assessed in newly weaned steers administered 1 of 3 treatments (n = 8 steers/treatment), consisting of 1) Mannheimia haemolytica vaccine (One Shot; Pfizer Inc., New York, NY), 2) Clostridium vaccine (UltraBac 7; Pfizer, Inc.), or 3) saline-injected control. Blood samples for the evaluation of APP concentrations were collected on d 0, 1, 3, 5, 7, 10, and 14 and steer BW measured on d 0 and 21 relative to treatment administration. Plasma concentrations of haptoglobin (Hp) increased (P < 0.05) in vaccinated but not control calves and reached a peak on d 3 and 5 for steers receiving Mannheimia haemolytica and Clostridium vaccine, respectively. Plasma concentrations of ceruloplasmin (Cp) and fibrinogen (Fb) increased (P < 0.05) in all calves after treatment administration and Fb concentrations were greatest (P < 0.01) in calves receiving Mannheimia haemolytica vaccine on d 3 and 5 compared with the other treatments. There were no treatment effects (P = 0.44) on 21-d steer ADG (0.43 kg/d; SEM = 0.082). In Exp. 2, 23 heifers were randomly assigned to 2 treatments: 1) vaccinated (Mannheimia haemolytica vaccine (One Shot; n = 12) and 2) saline control (n = 11). After vaccination, blood samples were collected for determination of APP concentrations on d 0, 3, 6, 9, 12, and 15. During this period, individual heifer DMI was measured using an automated feed intake measuring system (Model 4000E; GrowSafe Systems Ltd., Airdrie, Alberta, Canada). Initial and final shrunk BW did not differ (P > 0.36) among treatments. On d 1, plasma Cp concentrations increased (P < 0.01) sharply in vaccinated heifers but not control heifers and were greater (P < 0.05) in vaccinated vs. control heifers on d 3, 6, 9, and 12 relative to injection. Daily DMI did not differ (P = 0.66) among treatments (average = 9.1 kg/d; SEM = 0.34); however, ADG and G:F were greater (P ≤ 0.05) for control vs. vaccinated heifers (1.14 vs. 0.87 kg/d and 0.13 and 0.10 kg, respectively; SEM = 0.064 and 0.011). These data indicate that within a 2 wk period after vaccination, beef calves experience an acute-phase protein response, which may result in reduced ADG and feed efficiency.

Our objectives were to evaluate the dose/payout pattern of trenbolone acetate (TBA) and estradiol-17β (E(2)) implants and feeding of zilpaterol hydrochloride (ZH) on performance and carcass characteristics of finishing beef steers. A randomized complete block design was used with a 3 × 2 factorial arrangement of treatments. British × Continental steers (n = 168; initial BW = 362 kg) were blocked by BW and allotted randomly to 42 pens (7 pens/treatment; 6 pens/block; 4 steers/pen). The main effects of treatment were implant [no implant (NI); Revalor-S (REV-S; 120 mg of TBA + 24 mg of E(2)); and Revalor-XS (REV-X; 200 mg of TBA + 40 mg of E(2))] and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal before slaughter). Blocks were split into 2 groups, and block groups were fed for either 153 or 174 d. No implant × ZH interactions were noted for cumulative performance data. Overall, shrunk final BW (567, 606, and 624 kg for NI, REV-S, and REV-X, respectively), ADG (1.25, 1.51, and 1.60 kg), and G:F (0.14, 0.16, and 0.17) increased (P < 0.05) as TBA and E(2) dose increased. Implanting increased (P < 0.05) DMI, but DMI did not differ (P > 0.10) between REV-S and REV-X (8.8 for NI vs. 9.4 kg/d for the 2 implants). From d 1 to 112 of the feeding period, implanting increased (P < 0.05) ADG and G:F, but REV-S and REV-X did not differ (P > 0.10). From d 112 to end, ADG increased by 19% (P < 0.05) and G:F was 18% greater (P < 0.05) for REV-X vs. REV-S. Carcass-adjusted final BW (29-kg difference), ADG (0.2-kg/d difference), and G:F (0.02 difference) were increased (P < 0.05) by ZH, but daily DMI was not affected by feeding ZH. Hot carcass weight was increased (P < 0.05) by ZH (19-kg difference) and implant, with REV-X resulting in the greatest response (HCW of 376 for NI vs. 404 and 419 kg for REV-S and REV-X, respectively; P < 0.05). An implant × ZH interaction (P = 0.05) occurred for dressing percent (DP). Without ZH, implanting increased DP, but DP did not differ (P > 0.10) between REV-X and REV-S. With ZH, REV-X increased (1.7%; P < 0.05) DP vs. NI and REV-S. Marbling score, 12th-rib fat, and KPH were not affected (P > 0.10) by implant or ZH. Overall, treatment increased steer performance and HCW in an additive fashion, suggesting different mechanisms of action for ZH and steroidal implants. In addition, a greater dose of TBA + E(2) and extended payout improved steer performance and HCW.

Seventy-four beef heifers were used to evaluate relationships among performance, residual feed intake (RFI), and temperament measured as growing heifers (Phase 1) and subsequently as 3-yr-old lactating beef cows (Phase 2) in the same cohort. In both phases, females were housed in a covered facility and fed similar forage-based diets, and individual feed intakes, BW, BCS, chute scores (CS), exit velocities (EV), and pen scores (PS) were collected throughout the 70-d feeding trials. In Phase 2, cows were milked on trial d 14 (lactation d 28 ± 3.5) and trial d 70 (lactation d 84 ± 3.5) to determine energy-corrected milk (ECM) production. Ultrasonic backfat thickness (BF), and ribeye area (REA) were evaluated on d 0 and 70 of the trial in Phase 2. Heifers were ranked by RFI and placed into Low (<0.5 SD mean RFI; n = 27), Medium (within ± 0.5 SD; n = 23), and High (>0.5 SD mean RFI; n = 24) RFI groups. Body weight, BCS, and ADG were similar among all RFI groups; however, daily DMI differed for all groups (P < 0.01) and was greater (10.76 ± 0.24 kg/d) for High, intermediate (9.88 ± 0.25 kg/d) for Medium, and less (8.52 ± 0.23 kg/d) for Low RFI heifers. When cow performance was analyzed based on RFI rank as heifers, BW, BCS, ADG, RFI, d 14 and d 70 ECM, BF, and REA were similar among RFI groups; however, cows that were most efficient as heifers (Low) had decreased (P < 0.05) daily DMI values (10.30 ± 0.41 kg/d) compared with cows that ranked Medium (11.60 ± 0.44 kg/d) or High (11.50 ± 0.43 kg/d) as heifers. The Pearson rank correlation between Phase 1 and 2 RFI was r = 0.13 (P = 0.30), and Pearson rank correlations showed no relationship (P > 0.1) between RFI and temperament. Phase 1 CS was negatively associated with ADG in Phase 1 (r = -0.28; P = 0.02) and 2 (r = -0.32; P = 0.01), and positively associated with d 14 (r = 0.24; P = 0.04) and 70 (r = 0.25; P = 0.03) ECM. Phase 2 CS was negatively associated with Phase 2 ADG (r = -0.29; P = 0.01) and positively associated with d 14 (r = 0.46; P = 0.001) and 70 (r = 0.33; P = 0.004) ECM. Phase 2 PS also tended to be negatively associated with DMI in Phase 1 (r = -0.20; P = 0.096) and 2 (r = -0.20; P = 0.08). In this study, heifers that were most feed efficient subsequently consumed less feed as lactating cows and maintained similar performance. Feed efficiency was not associated with differences in temperament; however, more excitable females had poorer BW gains and tended to have reduced feed intakes but produced more ECM.