Supplemental trace minerals (zinc, copper, and manganese) as sulfates, organic amino acid complexes, or hydroxy trace-mineral sources for shipping-stressed calves.

Crossbred calves (n = 350; average BW 240 ± 1 kg) were obtained from regional livestock auctions. Within each set (block, n = 4), calves were stratified by BW and arrival sex into 1 of 8, 0.42-ha pens (10 to 12 calves per pen). Pens were assigned randomly to 1 of 3 treatments consisting of supplemental Zn (360 mg/d), Mn (200 mg/d), and Cu (125 mg/d) from inorganic (zinc sulfate, manganese sulfate, and copper sulfate; n = 2 pens per block), organic (zinc amino acid complex, manganese amino acid complex, and copper amino acid complex; Availa-4, Zinpro Corp., Eden Prairie, MN; n = 3 pens per block), and hydroxy (IntelliBond Z, IntelliBond C, and IntelliBond M; Micronutrients, Indianapolis, IN; n = 3 pens per block) sources. During the 42- to 45-d backgrounding period calves had ad libitum access to bermudagrass hay and were fed corn and dried distillers grain-based supplements that served as carrier for the treatments. After removal of data for chronic (n = 6) and deceased (n = 1) calves, trace-mineral source had no effect on final or intermediate BW (P = 0.86) or ADG (P ≥ 0.24). With all data included in the analysis, dietary treatments had no effect on the number treated once (P = 0.93), twice (P = 0.71), or 3 times (P = 0.53) for bovine respiratory disease or on the number of calves classified as chronic (P = 0.55). Based on these results, trace-mineral source had no effect on total BW gain, ADG, or morbidity during the receiving phase in shipping-stressed cattle.

Effects of monensin and tylosin in finishing diets containing corn wet distillers grains with solubles with differing corn processing methods.

A total of 3,632 crossbred steers were used in 3 separate randomized complete-block designed finishing experiments. Data from Exp. 1 were analyzed separately whereas data were combined for Exp. 2 and 3, based on corn processing method used [Exp.1 = equal combination of dry-rolled and high-moisture (DRC:HMC); Exp. 2 and 3 = steam-flaked (SFC)]. Steers were fed 1 of 5 treatments to evaluate the effects of monensin and tylosin in feedlot diets containing 25% corn wet distillers grains with solubles (WDGS; DM basis). Treatments included: 1) corn-based diet (no WDGS) with 360 mg/d monensin and 90 mg/d tylosin (CORN+MT), 2) 25% wet distillers grains with solubles (WDGS-CON), 3) 25% WDGS with 360 mg/d monensin (WDGS+M), 4) WDGS with monensin and tylosin at same levels as treatment 1, and 5) WDGS with 480 mg/d monensin and 90 mg/d tylosin (WDGS+HIMT). In Exp. 1, WDGS+MT increased (P < 0.01) ADG (6.5%), G:F (6.9%), and HCW (3.0%) compared with CORN+MT. Alternatively, in Exp. 2 and 3, WDGS+MT had no effect on ADG (P = 0.18), decreased (P < 0.01) G:F by 3.2%, and did not affect HCW (P = 0.57) compared with CORN+MT. In Exp. 1, addition of monensin to a WDGS diet increased G:F by 3.1% (P = 0.03) and tended to increase G:F in Exp. 2 and 3 (P = 0.09) compared with WDGS-CON. For all experiments, addition of monensin and tylosin in a diet containing WDGS increased G:F (P < 0.01) and reduced total and severe liver abscesses (P < 0.01) compared with WDGS-CON. Additionally, HCW was increased in Exp. 2 and 3 (P < 0.01) and tended to increase in Exp. 1 (P = 0.09) when monensin and tylosin were fed in a WDGS diet compared with WDGS-CON. Feeding WDGS+MT reduced total liver abscesses by 79.3% (Exp. 1) and 57.6% (Exp. 2 and 3) compared with WDGS-CON. Compared with WDGS+MT, minimal differences were observed when monensin was fed at 480 mg/steer daily with tylosin in diets containing WDGS. Inclusion of WDGS in finishing steer diets did not alter effectiveness of monensin with tylosin in improving G:F and reducing prevalence of liver abscesses, regardless of corn processing method. Corn processing method appears to be an important factor in performance response to WDGS with feeding value of WDGS, measured as an increase in feed efficiency, being greater in a DRC:HMC-based diet compared with a SFC-based diet.

Effects of ractopamine and trenbolone acetate implants with or without estradiol on growth performance, carcass characteristics, adipogenic enzyme activity, and blood metabolites in feedlot steers and heifers.

Two experiments were conducted to evaluate effects of ractopamine (RAC) and steroidal implant treatments on performance, carcass traits, blood metabolites, and lipogenic enzyme activity in feedlot cattle. In Exp. 1, yearling steers (n = 486; initial BW = 305 kg) were used in a 3 × 3 factorial arrangement of RAC doses of 0 (R0), 100 (R100), or 200 (R200) mg·steer(-1)·d(-1) fed for 28 d and implant regimens (implant-reimplant) of no implant-no reimplant (NI-NI), 120 mg of trenbolone acetate (TBA) and 24 mg of estradiol-17ß (E17B)-no implant (RS-NI), or 80 mg of TBA and 16 mg of E17B followed by 120 mg of TBA and 24 mg of E17B (RI-RS). Except for KPH and skeletal maturity score, no RAC × implant interactions were noted (P > 0.10). Carcasses from R200 were 6.3 kg (P = 0.042) heavier than those from R0. Marbling, calculated empty body fat (EBF), and USDA quality grade did not differ (P > 0.10) among RAC treatments. The RI-RS steers had 12.6 kg (P = 0.001) and 41.1 kg (P < 0.001) greater HCW than RS-NI and NI-NI, respectively. Despite no difference (P > 0.10) in EBF, marbling score was decreased for RI-RS (P < 0.001) and RS-NI (P = 0.001) relative to NI-NI, resulting in 14.6 and 11.4 percentage unit fewer USDA Prime and Choice carcasses with RI-RS (P = 0.008) and RS-NI (P = 0.039) than with NI-NI. In Exp. 2, heifers (n = 48; initial BW = 347 kg) were used in a 3 × 2 factorial arrangement of RAC doses of 0 (R0) or 250 (R250) mg·heifer(-1)·d(-1) and implant regimens of none (NI), 200 mg of TBA (TO), or 200 mg of TBA and 20 mg of E17B (TE). Blood samples were collected at various times during the feeding period, and subcutaneous adipose samples were collected on d 119. For growth and carcass measurements, no RAC × implant interactions (P > 0.10) were detected. The RAC-supplemented heifers had greater HCW (P < 0.10) with no difference in marbling score. For implant regimens, TE heifers had greater HCW than the NI (P = 0.001) and TO (P = 0.037) heifers. Although EBF did not differ among implant treatments (P > 0.10), TE (P = 0.021) and TO (P = 0.039) had fewer Choice carcasses than NI. Heifers with implants had decreased cortisol and increased IGF-1 and NEFA (P < 0.10) compared with NI heifers. An implant × RAC interaction was detected (P = 0.001) for serum urea nitrogen (SUN), with TE and RAC-supplemented heifers having decreased SUN. These data suggest that the effects of implant and RAC on growth and carcass traits are independent and that USDA quality grade and marbling score can differ significantly among carcasses with similar calculated EBF values.

Effects of ractopamine and sex on serum metabolites and skeletal muscle gene expression in finishing steers and heifers.

We evaluated growth-related responses to ractopamine in steers and heifers. Sixteen Angus steers (512 kg) and 16 Angus heifers (473 kg) housed in individual pens were used in a complete block design. At 90 to 97 d before the experiment, steers were implanted with 120 mg of trenbolone acetate and 24 mg of estradiol-17beta (Component TE-S) and heifers were implanted with 140 mg of trenbolone acetate and 14 mg of estradiol-17beta (Component TE-H). Treatments were arranged as a 2 x 2 factorial and included sex (steer vs. heifer) and ractopamine-HCl (0 or 200 mg/d). Cattle were fed a diet based on steam-flaked corn once daily. Blood and LM and biceps femoris (BF) biopsy samples were collected on d 0 (before ractopamine feeding) and after 14 and 28 d of ractopamine feeding. Serum insulin concentrations were not affected by ractopamine or sex. Serum IGF-I concentrations were greater in steers than heifers (P < 0.001), and steers demonstrated greater IGF-I mRNA expression in BF than heifers (P = 0.05). Ractopamine decreased serum IGF-I concentrations in heifers on d 14, but increased serum IGF-I concentrations in steers on d 28 (sex x ractopamine x day interaction; P = 0.03). Ractopamine did not affect (P >or= 0.19) mRNA expression of IGF-I, IGFBP-3, or calpastatin in BF or LM. However, ractopamine led to increases in LM expression of IGFBP-5 in heifers, but to decreases in expression in steers (ractopamine x sex interaction; P = 0.04). Ractopamine decreased myosin heavy chain IIA mRNA expression in BF (P = 0.04) but not in LM (P = 0.99). Ractopamine decreased beta(2)-receptor mRNA expression in LM of steers on d 14, but not on d 28; in contrast, expression of beta(2)-receptor mRNA in LM of heifers was not affected by ractopamine (sex x ractopamine x day interaction; P = 0.03). Although there were a few criteria for which ractopamine led to differences in response between steers and heifers, there were no striking disparities to suggest that the effectiveness of ractopamine would markedly differ between sexes.

Effects of ractopamine supplementation and postmortem aging on longissimus muscle palatability of beef steers differing in biological type.

Effects of ractopamine hydrochloride (RAC) supplementation and postmortem aging on palatability of beef from steers differing in biological type were evaluated using LM samples from British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 98/type). Equal numbers of steers within each type were assigned to treatments of 0 or 200 mg.steer(-1).d(-1) of RAC fed during the final 28 d of the finishing period. Warner-Bratzler shear force (WBSF) was measured at 3, 7, 14, and 21 d postmortem, and trained sensory panel (TP) evaluation was conducted using LM samples aged for 14 d postmortem. A RAC x type interaction (P = 0.006) was detected for WBSF. Within each type, steers fed RAC produced steaks with greater (P < 0.05) WBSF values than steaks from control steers; however, the magnitude of the effect of RAC on WBSF was more pronounced among Brahman cross-breds (5.53 vs. 4.96 +/- 0.10 kg) than among Continental crossbred (4.16 vs. 3.96 +/- 0.10 kg) and British steers (4.10 vs. 3.75 +/- 0.10 kg). The effect of RAC on WBSF, though diminished slightly by aging (mean WBSF difference: 3 d = 0.49 kg; 21 d = 0.24 kg), was not completely mitigated by 21 d of postmortem storage (P(RAC x AGE) = 0.16). Steers fed RAC produced steaks that received lower (P < 0.05) TP ratings for tenderness (8.09 vs. 8.95 +/- 0.18) and juiciness (7.41 vs. 8.07 +/- 0.16 kg), along with slightly lower (P = 0.06) ratings for beef flavor (6.67 vs. 6.93 +/- 0.10 kg), compared with steaks from unsupplemented steers, regardless of biological type. Among the 3 biological types, Brahman crossbred cattle produced steaks with the greatest (P < 0.05) WBSF values at each aging period; WBSF values for steaks from British and Continental type steers did not differ (P > 0.05) at any aging time. Sensory panel ratings of tenderness, juiciness, and beef flavor were greatest (P < 0.05) for steaks from British steers, and least (P < 0.05) for steaks produced by Brahman-type steers. Results from this study suggest that RAC supplementation slightly decreases LM tenderness (WBSF and TP) of British, Continental crossbred, and Brahman cross-bred steers, and that the effect of RAC on WBSF may be more pronounced in steaks from Brahman crossbred cattle than among stenks from Continental type or British steers.

The development of potentially better practices to support the neurodevelopment of infants in the NICU.

OBJECTIVE: To review the existing evidence used to identify potentially better care practices that support newborn brain development. STUDY DESIGN: Literature review. RESULT: Sixteen potentially better practices are identified and grouped into two operational clinical bundles based upon timing for recommended implementation. CONCLUSION: Existing evidence supports the implementation of selected care practices that potentially may support newborn brain development.

Implementing potentially better practices to support the neurodevelopment of infants in the NICU.

OBJECTIVE: The purpose of the Vermont Oxford Neonatal Quality Improvement Collaborative 2005 was to explore improvements related to the physical environment of the newborn intensive care unit (NICU) in order to optimize the neurodevelopmental outcome of newborns. STUDY DESIGN: Five centers were involved in a focus group examining NICU environmental design and its impact on the neurodevelopmental outcome of the neonate. Using an evidence-based approach, the group identified 16 potentially better care practices. This article describes the implementation approaches for some of these practices. The practice areas include tactile stimulation, providing early exposure to mother's scent, minimizing exposure to noxious odors, developing a system for noise assessment of the NICU acoustic environment, minimizing ambient noise in the infants environment, and preservation of sleep. RESULT: Approaches to implementation were center specific. Optimizing neurodevelopment of the newborn was the desired goal, but this outcome is difficult to measure with a limited number of subjects over a short study period. Many of the changes although intuitively beneficial are difficult to measure. Education of all participants was considered essential to the process of implementation. CONCLUSION: The process of collaborative quality improvement is useful in identifying ways to optimize the physical environment of the NICU to improve the neurodevelopmental outcome of the neonate.

Effects of ractopamine supplementation on growth performance and carcass characteristics of feedlot steers differing in biological type.

Effects of ractopamine hydrochloride (RAC) supplementation on growth performance and carcass characteristics of feedlot steers differing in biological type were investigated using British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 420). Steers of each type were weighed at reimplantation [British, mean BW = 375 kg (SD = 38 kg); Continental crossbred, mean BW = 379 kg (SD = 42 kg); Brahman crossbred, mean BW = 340 (SD = 32 kg)] and sorted into 7 BW blocks, each block consisting of 2 pens (10 steers per pen) per type. Pens within a block x type subclass were randomly assigned to RAC treatments (0 or 200 mg x steer(-1) x d(-1) fed during the final 28 d of the finishing period). The type x RAC interaction did not affect (P > 0.05) any of the traits evaluated in this study. Feeding RAC improved (P = 0.001) ADG (1.50 vs. 1.73 +/- 0.09 kg) and G:F (0.145 vs. 0.170 +/- 0.005), but did not affect (P = 0.48) DMI of steers. Dressing percentage, adjusted fat thickness, KPH percentage, and yield grade were not affected by RAC supplementation. Carcasses of steers fed RAC had heavier (P = 0.01) HCW (359 vs. 365 +/- 4.9 kg), larger (P = 0.046) LM areas (81.7 vs. 84.0 +/- 1.1 cm(2)), and tended (P = 0.07) to have lower mean marbling scores (487 vs. 477 +/- 5.2; Slight = 400, Small = 500) than did carcasses of control steers. Among the 3 biological types, Brahman crossbred steers had the lowest DMI and produced the lightest-weight carcasses that had the lowest mean marbling score (P < 0.05). Compared with Continental crossbred and Brahman crossbred steers, British steers produced carcasses with the greatest (P = 0.001) mean marbling scores. Continental crossbred steers had the heaviest BW and greatest dressing percentages and produced the heaviest carcasses with the largest LM areas (P < 0.05) compared with British and Brahman crossbred steers. In the present study, 28 d of supplementation with RAC at a dosage rate of 200 mg x steer(-1) x d(-1) elicited consistent responses in growth performance and carcass traits among 3 diverse biological cattle types.

Effects of ractopamine supplementation on behavior of British, Continental, and Brahman crossbred steers during routine handling.

Equal numbers of British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 420) were used to examine the effects of ractopamine supplementation and biological type on behavior during routine handling. Steers were blocked by BW within type and allocated to pens, resulting in 2 pens (10 cattle per pen) representing each block x type subclass. Pens within each block x type subclass then were randomly assigned to ractopamine supplementation treatments (0 or 200 mg.steer(-1).d(-1)), which were administered during the final 28 d of the finishing period. At the time final BW were obtained (28 d after treatment initiation), a single, trained observer, blinded with respect to treatment designations, recorded subjective scores to characterize behavior of each animal. Scores included entry force score (degree of force required to load the animal into the chute); entry speed score (walk, trot, run); chute behavior score (calm, restless shifting, moderate struggling); and exit speed score (walk, trot, run). Ractopamine supplementation had no effect on entry force score, chute behavior score, or exit speed score; however, cattle supplemented with ractopamine entered the chute more rapidly than did control cattle. Biological cattle type was a significant source of variation in entry force score and exit speed score. Continental crossbreds required greater (P < 0.05) force to enter the squeeze chute than did Brahman crossbred or British steers. In addition, Continental crossbred and Brahman crossbred steers left the processing chute with the greatest speed, whereas British steers exited the processing chute most slowly. Biological cattle type did not affect scores for entry speed or behavior during restraint in the chute. No adverse effects of ractopamine supplementation on cattle behavior were observed in this study.

Bacterial flora of liver abscesses in feedlot cattle fed tylosin or no tylosin.

Bacterial flora of liver abscesses from cattle fed tylosin or no tylosin and susceptibilities of the predominant bacterial isolates to tylosin and other antimicrobial compounds were determined. Abscessed livers were collected at slaughter from cattle originating from feedlots that had fed tylosin (n = 36) or no tylosin (n = 41) for at least 2 yr, and segments of livers with one or two intact abscesses were transported to the laboratory. Abscesses were cultured for anaerobic and facultative bacteria. Fusobacterium necrophorum, either as single culture or mixed with other bacteria, was isolated from all abscesses. The incidence of subsp. necrophorum, as part of the mixed infection, was lower (P < .05) in the tylosin group than in the no-tylosin group (33 vs 61%). However, the incidence of Actinomyces pyogenes was higher (P < .01) in the tylosin group than in the no-tylosin group (53 vs 10%). Totals of 119 F. necrophorum and 21 A. pyogenes isolates were used for determinations of susceptibilities to bacitracin, oxytetracycline, chlortetracycline, lasalocid, monensin, tylosin, tilmicosin, and virginiamycin. The minimum inhibitory concentrations (MIC) of antibiotics were determined with a broth microdilution method. The mean MIC of tylosin for F. necrophorum and A. pyogenes were not different between isolates from tylosin and no-tylosin groups. We concluded that continuous feeding of tylosin did not induce resistance in F. necrophorum or A. pyogenes. Also, the higher incidence of mixed infection of F. necrophorum and A. pyogenes in liver abscesses of tylosin-fed cattle suggests a potential synergistic interaction between the two organisms in causing liver abscesses.

Effects of tilmicosin on acute undifferentiated respiratory tract disease in newly arrived feedlot cattle.

OBJECTIVES: To evaluate effects of tilmicosin when used in fever-based and metaphylactic treatment programs to attenuate acute undifferentiated bovine respiratory disease (BRD) in cattle that recently arrived at feedlots, and to evaluate the effects of tilmicosin for the treatment of BRD. DESIGN: Randomized-block controlled study. ANIMALS: 1,639 calves from livestock auctions. PROCEDURES: Cattle were assigned to 3 groups. Cattle in the nonmedicated (control) group were not given antibiotics during processing. Cattle in the fever-based treatment group were given tilmicosin (10 mg/kg [4.5 mg/lb] of body weight, s.c.) during processing when their rectal temperature was > or = 40 C (104 F). All cattle in the metaphylactic treatment group were given tilmicosin (10 mg/kg, s.c.) during processing. Calves with BRD were treated with tilmicosin (10 mg/kg, s.c.). RESULTS: Morbidity rates in the metaphylactic (30.4%) and fever-based (44.7%) treatment groups were less than that for the nonmedicated group (54.8%). Mortality rate for the metaphylactic group during the first 28 days (1.1%) and during the entire study (1.7%) was less than that for the nonmedicated group (3.3 and 4.6%, respectively). Differences were not observed in therapeutic response rates among calves with BRD that were treated. CLINICAL IMPLICATIONS: Fever-based and metaphylactic treatment programs that used tilmicosin decreased the prevalence of BRD and improved growth of calves. Metaphylactic treatment decreased the number of fatalities caused by BRD in high-risk calves. Fever-based treatment was less effective than metaphylactic treatment for decreasing the prevalence of BRD in newly arrived cattle.

Comparison of Infasurf (calf lung surfactant extract) to Survanta (Beractant) in the treatment and prevention of respiratory distress syndrome.

OBJECTIVE: To compare the relative safety and efficacy of Infasurf (calf lung surfactant extract; ONY, Inc, Amherst, NY, IND #27169) versus Survanta (Beractant, Ross Laboratories, Columbus, OH) in reducing the acute severity of respiratory distress syndrome (RDS) when given at birth and to infants with established RDS. DESIGN: A prospective, randomized, double-blind, multicenter clinical trial. SETTING: Thirteen neonatal intensive care units participated in the treatment arm: seven of these concurrently participated in the prevention arm. PATIENTS: The treatment arm enrolled infants of

Effect of monensin and monensin and tylosin combination on feed intake variation of feedlot steers.

A trial involving four commercial feedlots and an individual feeding trial evaluated the effect of monensin and monensin/tylosin on intake variation and deaths from digestive disorders. Four commercial feedlots in Texas and Colorado fed 2,904 yearling crossbred steers (340 kg) high-grain diets containing approximately 82% grain, 8% silage and alfalfa hay, 4% fat, and 6% supplement (DM basis). Steers were allotted randomly to one of three monensin/tylosin levels: 1) no monensin or tylosin (control); 2) 22 mg/kg of monensin and 11 mg/kg of tylosin; or 3) 33 mg/kg of monensin and 11 mg/kg of tylosin. Monensin/tylosin reduced DMI (P < .05) and improved ADG (P < .05) and feed efficiency (P < .01). Intake variation associated with dry matter offered per pen was not different among treatments. In the individual feeding trial, feeding 27 mg/kg of monensin reduced (P < .10) DMI variation during grain adaptation and during d 57 to 70 and d 97 to 110 compared with the control (no monensin) diet. The magnitude of intake variance was 5 to 10 times greater with individually fed steers than with steers fed in the commercial feedlot pens. When the DMI of the individually fed steers were averaged and treated as a pen of steers, DMI variance was reduced drastically and was not different between treatments. We interpret these data to indicate that monensin and monensin/tylosin reduce feed intake variation among individual steers within a pen of steers. Pen means mask individual animal variation to the point that it is difficult to detect treatment differences.

Comparative age-related acute and chronic pulmonary oxygen tolerance in rats.

Young rats are thought to be more tolerant to hyperoxia. We propose that this may not be proven and depends on how tolerance is defined. We assessed oxygen tolerance in Sprague-Dawley rats from birth to maturity by comparing survival, lung water, antioxidant enzyme activity, lung morphometrics, heart weight, and arterial blood gases in newborn and 27-, 44-, 48-, and 96-day-old rats exposed to 100% O2 or room air for 22 days. Some 96-day-old rats (rest group) received only 50% O2 between 48 and 72 h. Mortality after 5 days of O2 was 0% in newborn and 27-day-old rats and 27% in 44-day-old rats but was > 80% in 48- and 96-day-old rats. Between 5 and 22 days, the death rate was 100% in newborns, 25% in 27-day-old rats, and 0% in 44- to 96-day-old rats. Death occurred when lung water was > 84% except in newborns, which tolerated high lung water for the first 7 days. In chronically exposed 44- and 96-day-old rats, lung water returned to normal. Enzyme activity increased with O2 at all ages but did not relate to survival. In 96-day-old rats, the initial increase was suppressed on day 3. All chronically O2-exposed rats had minimal nonvascular parenchymal changes but developed right ventricular hypertrophy and increased alveolar ductal artery muscularization and lost alveolar capillaries. The most mature rats were least affected. In O2, there was pulmonary insufficiency the first 3 days, followed by recovery, and later hypercarbia and decreased arterial PO2. We conclude that young rats, 0-44 days old, are more O2 tolerant for 5 days. More mature animals, surviving 5 days, are more tolerant to chronic exposure.

Effect of sequential implanting with zeranol on steer lifetime performance.

Three trials involving 513 exotic crossbred steers were conducted to determine the effect of zeranol implanting in the suckling and growing phases on subsequent feedlot performance and carcass characteristics. Treatments were 1) unimplanted control, 0000; 2) implanted twice in the finishing phase, 00II; 3) implanted in the growing phase and twice in the finishing phase, 0III; 4) implanted in the suckling phase and twice in the finishing phase, I0II; 5) implanted in the suckling and growing phases with a single implant in the finishing phase, III0; and 6) implanted in the suckling and growing phases and twice in the finishing phase, IIII. Implanting in the suckling period did not significantly affect preweaning gain. Implanting in the growing period produced a treatment x trial interaction (P less than .05), but zeranol increased gains by an average of 8.4% over the three trials. Growing period gain was not influenced by implanting during suckling. Implanting twice during the finishing period increased gain (P less than .05) over unimplanted and III0 steers. Finishing gain was not influenced by previous suckling and(or) growing implant treatment. Lifetime ADG of steers was increased (P less than .05) by all implant treatments compared with unimplanted controls. Zeranol tended (P = .14) to improve feed conversion in the finishing phase. All implant treatments increased hot carcass weight (P less than .05), and all but III0 reduced fat deposition, as indicated by lower quality grade (P less than .05). Other carcass characteristics were not significantly affected by treatment. These trials demonstrated that implanting in the suckling and(or) growing phases of production did not reduce performance in the finishing phase.