Objective: This study evaluated the effects of feeding beef cattle finishing diets with greater than 14.0% dietary CP and with or without ractopamine hydrochloride (RH) on growth performance, carcass merit, net energy utilization, and metabolizable protein balance. Materials and Methods: Heifers (n = 525) were assigned to 48 pens in a generalized complete block design, and pens of cattle were assigned randomly to 0 or 400 mg of RH/animal per day and 3 CP treatments in a 2 x 3 factorial arrangement (n = 8 pens/treatment) fed for 35 d before slaughter. Dietary protein treatments were steamflaked corn-based diets containing 13.9% CP, 8.9% RDP, and 5.1% RUP (CON); 20.9% CP, 14.4% RDP, and 6.5% RUP (High RDP); or 20.9% CP, 9.7% RDP, and 11.2% RUP (High RUP) on a DM basis. Results and Discussion: No RH x CP interactions were observed. Final BW, ADG, water disappearance, DMI, and G:F were not different among CP treatments. Dressing percentage was greater for cattle fed High RDP than for those fed High RUP, but other carcass outcomes RUP, intermediate for High RDP, and least for CON. CatRH. Dietary CP requirements were greater for cattle fed 400 compared with 0 mg of RH but did not exceed the CP supplied by CON, High RDP, or High RUP. Implications and Applications: Feeding greater than 14.0% CP does not negatively affect performance or carcass characteristics of finishing cattle, and the absence of interactions between CP and RH suggests that RH does not increase CP requirements above those provided in a typical finishing cattle diet.

Liver abscess (LA) prevalence has increased 15% for beef cattle and 25% for Holstein cattle. The prevalence of liver abscesses in the Central Plains region (CR) is greater than the Southwest region (SR) of the United States. The objective was to evaluate soil organic matter (SOM) microbiome of feedlot pens, associated LA microbiomes, and the impact of breed, location, and tylosin. Eighty-three commercial feedlot pens were sampled for SOM prior to harvesting and LA samples were collected from two commercial packing plants in Tolleson, AZ (SR) and Greely, CO (CR). Liver abscess samples were linked to SOM samples. Amplification and sequencing of the V4 variable region of the 16S rRNA gene was performed using the Illumina MiSeq. Bacterial phyla, genera, and diversity indices were reported for LA and SOM samples. Reported data is from a subset of five pens. The most prevalent genera identified in liver abscesses were Fusobacterium (64.2%) and Bacteroides (18.6%). Predominant SOM genera were Atopostipes (13%) and Clostridium (10%). Phylum SOM Shannon Weiner Index (SWI) was lower for the CR compared to the SR (0.034 vs. 0.174; P < 0.05), indicating a dominant bacterium in the CR. Atopostipes and Clostridium comprised 48% of the CR SOM, explaining the lower SWI. The SWI of SOM and liver abscesses of Holsteins are lower (P < 0.05) compared to beef counterparts. Additionally, Clostridium, Fusobacterium, and Atopostipes populations were greater (P < 0.05) in SOM of Holstein pens than beef pens. Genus richness was lower (P < 0.05) for both SOM and liver abscesses from pens of cattle fed tylosin vs. no tylosin. There is a negative correlation between SOM SWI and LA% (R2 = -0.49; P = 0.03) and LA severity (A+) (R2 = -0.44; P = 0.05). In conclusion, SOM may serve as a potential vector for liver abscesses.

Cross-bred heifer calves (n = 579; initial bodyweight 404 ± 27.4 lb; 183.3 ± 12.4 kg) were utilized in a randomized, complete block design to compare 3 different antibiotics for control of bovine respiratory disease (BRD) in light-weight feeder heifers. Cattle originated from southeast Texas and were shipped approximately 700miles(1125 km) to the Clayton (New Mexico) Livestock Research Center. Heifers were randomly allocated off the truck into 30 pens, and administered 1 of 3 metaphylactic treatments at initial processing: 1) tulathromycin (TUL; 1.13 mg/lb (2.5 mg/kg)); 2) tilmicosin (TIL; 6 mg/lb (13.3 mg/kg)); or 3) gamithromycin (GAM; 2.72 mg/lb (6.0 mg/kg)). Heifers administered TUL had 0.29 lb (0.13 kg) greater (95% Cl = 2.27 to 2.46) average daily gain than cattle administered GAM. Cattle administered TUL had a lower (5.2%; 95% Cl = 1.2 to 9.1) morbidity rate than calves in the TIL (14.6%; 95% Cl = 6.7 to 22.5) and GAM (12.79%; 95% Cl = 7.7 to 17.9) groups. There were no differences in DM I or mortality in cattle between treatments.

Steam-flaked corn is commonly fed in feedlot finishing diets because steam-flaking improves starch availability and nutrient utilization, thus improving the overall feeding value of corn. In most operations which utilize steam-flaked corn, grain is processed to a pre-determined flake density by setting the rolls to a specific separation distance and using tension to hold rolls together. Flaked grain is most often produced to a bulk density between 24 and 32 lb/bu, with a common recommendation of 27 lb/bu for corn; however, flake density among steam-flakers within a single mill and among feedlots can vary greatly. Flaking to a similar density using 2 flakers does not ensure similar starch availability.

Cattle receiving zilpaterol hydrochloride () may recycle less N and require a greater supply of RDP. This study evaluated effects of ZH on performance and carcass characteristics of steers fed diets with increasing dietary RDP concentrations supplied as urea. Steers (429 animals; BW = 423 ± 4.5 kg) were sorted into 3 blocks according to BW and assigned to 1 of 6 treatments (6 pens per treatment) in a randomized complete block design. Treatments were a 2 × 3 factorial arrangement of either no ZH or ZH (75 mg ZH per steer daily) supplemented to finishing diets containing 0, 0.5, or 1.0% urea of dietary DM. Pen weights were recorded before treatment initiation; urea was fed for 27 d, and ZH treatments were fed for 24 d with a 3-d withdrawal period. Pen weights were recorded before transporting steers to a commercial abattoir. Continuous response variables were analyzed using the MIXED procedure and categorical data were analyzed using the GLIMMIX procedure of SAS. No ZH × dietary urea interactions ( ≥ 0.14) occurred for all performance and carcass response variables. Feeding ZH for the last 27 d (included a 3-d withdrawal period) of the finishing period increased ( < 0.01) ADG, decreased ( < 0.01) DMI, and increased ( < 0.01) G:F compared with no ZH. In addition, ZH increased HCW ( < 0.01), dressing percentage ( < 0.01), LM area ( < 0.01), and decreased ( = 0.01) yield grade. Increasing dietary urea linearly decreased ( = 0.01) ADG and DMI. A tendency for a linear decrease ( = 0.10) in HCW, and a tendency for a quadratic increase ( = 0.07) in marbling score were observed as urea increased in the diet. Results indicate that cattle supplemented with ZH do not require additional RDP in the diet, and that performance and carcass characteristics were negatively affected when urea was increased in the diet.

Liver abscesses in feedlot cattle are a major economic, welfare, and production concern to the cattle feeding industry. Severe liver abscesses (LA) reduce ADG by as much as 0.20 kg, DMI by 5%, trimming loss by 0.43%, carcasses grading choice by 7%, and HCW by 36 kg. In processing facilities, LA introduce operational and food safety concerns. These include a reduction in processing efficiency, lost time as a result of line stoppages, and offal condemnation in addition to the consumer risk associated with LA contamination of edible meat. Tylosin phosphate, a macrolide antibiotic, has been shown to reduce LA by 75% and level of Fusobacterium Necrophorum in the rumen by 80 to 90%. During this initial observational study, a total of 83 feedlot pens (each individual feed yard exceeding 40,000 head capacity) within three geographical regions (Arizona, Colorado, and the Texas Panhandle) were sampled. Feedlot pen data were collected within 1 wk before harvest and cattle were traced to the packing plant. Every third rumen and its matching liver were tagged (if condemned only). Rumens were scored for consolidation, scars, moderate and acute lesions, and a sample was taken. Livers were scored based on an adaptation of the Elanco Liver Check scoring system. Holstein cattle had a greater (P < 0.05) percentage of LA than beef breeds (30.3 vs. 20.0%). Additionally, Holstein cattle had 11% severe LA (A+) compared with 4% for beef breeds (P < 0.05). No geographical difference (P ≥ 0.10) were detected for liver abscess prevalence and averaged 23, 25, and 26% for the Texas Panhandle, Arizona, and Colorado regions, respectively. Liver abscess rate and severe LA (A+) incidence differed between feedlots (P < 0.05) with within feedlot variation. A correlation was observed for LA% and days on feed (R2 = 0.22; P = 0.04) and for LA % and breed (R2 = 0.29; P = 0.01). No correlation was observed between LA percentage and tylosin phosphate, and between LA percentage and rumen lesions (P ≥ 0.10). These data indicated no association between LA and rumen damage as a result of acidosis. Rumen lesions averaged 12.2%, of which 9.3% were consolidated, 2.4% scar tissue, and the remainder moderate and acute lesions. This study justifies further investigation of feedlot soil and manure as the source of LA causing pathogens to evaluate the within feedlot variation observed for in LA percentage in cattle.

This study evaluated if excess protein decreases performance and carcass quality of finishing cattle fed diets with or without ractopamine hydrochloride (RH). Heifers were assigned to 48 pens in a randomized complete block design and pens of cattle were randomly assigned to 3 protein and 2 RH (0 vs. 400 mg/day) treatments. Protein treatments were steam-flaked corn-based diets containing 13.9% CP, 8.8% RDP, and 5.0% RUP (CON), 20.9% CP, 13.4% RDP, 6.1% RUP (High RDP), or 20.9% CP, 9.1% RDP, 10.4% RUP (High RUP). Cattle were weighed at initiation of RH and at shipping. No RH × CP interactions (P ≥ 0.11) occurred for performance or carcass traits. Excess CP did not affect (P ≥ 0.12) final BW or ADG. Carcass-adjusted final BW and ADG tended to be greater (P = 0.06) for cattle receiving High RDP than High RUP and CON. Water intake, DMI, G:F, and carcass-adjusted G:F were not different (P ≥ 0.12) among CP treatments. Hot carcass weight tended to be greater (P = 0.06) for cattle receiving High RDP than High RUP and CON. Dressing percentage was lower (P < 0.01) for cattle fed High RUP than High RDP and CON. Marbling score, 12th rib fat depth, LM area, and yield grade were not different (P ≥ 0.16) among CP treatments. Heifers receiving High RUP tended to have lower (P = 0.10) KPH than CON. Percentage choice tended to be greater (P = 0.09) for heifers receiving High RDP vs. High RUP. Water and DMI were not different (P ≥ 0.36) for RH vs. no RH. Cattle receiving RH had greater (P < 0.01) final BW, ADG, carcass- adjusted final BW, and carcass-adjusted ADG, and lower (P < 0.01) G:F and carcass-adjusted G:F compared with no RH. Hot carcass weights were greater (P < 0.01) and dressing percentage tended to be greater (P = 0.09) for cattle receiving RH, while marbling score was not affected (P = 0.11) by RH. Twelfth-rib fat depth tended to be lower (P = 0.08), and KPH was lower (P = 0.02) for RH vs. no RH. The LM area was greater (P = 0.03) for cattle receiving RH vs. no RH. Excess CP does not negatively impact performance or carcass traits of finishing cattle, and no interactions between CP and RH suggest that CP requirements are not affected by RH.

The 2015 feedlot consulting nutritionist survey is a collaborative project between New Mexico State University and Texas Tech University that focuses on summarizing the professional practices of consulting feedlot nutritionists and updates a 2007 survey. Forty-nine consulting feedlot nutritionists were asked to participate, of which 24 completed the survey. The nutritionists surveyed service over 14,000,000 cattle annually and were representatives from individual consulting practices (54.2%), corporate cattle feeding companies (20.8%), corporate feed manufacturing companies (20.8%), or a combination of consulting practices (4.2%). The survey was completed using a web-based survey tool and contained 101 questions that were divided into sections regarding general information about the consulting practice; general cattle management; receiving cattle management, diet adaption; mixers, feed mills, and feeding management; grains and grain processing; grain by-product use; roughage use; information about supplements and microingredients; liquid feed use; nutrient formulation; feed additive use; and information used as a basis for nutritional recommendations. In most cases, the results of the current survey were similar to those reported for the 2007 survey, with a few notable exceptions such as shifts in cattle numbers and preferences for specific feedstuffs. The present study introduced a number of new questions not included in the 2007 survey that focused on management strategies used in the receiving period. Data from this survey provide insight into current nutritional and management practices of consulting nutritionists and, as in past surveys, should be useful for informing national committees that make nutritional recommendations for cattle, as well as nutrition and management strategies employed within university research settings.

This study evaluated blood parameters, health, and performance of immune-stimulated and hay-supplemented feedlot receiving calves. Heifers (n = 705; 179 ± 0.58 kg BW) were blocked by six truckloads and assigned to 48 pens and four treatments in a randomized complete block design. Treatments were a factorial arrangement of hay (+HAY vs. –HAY) and immunostimulation (+IMMUN vs. –IMMUN). Pens assigned +HAY received supplemental alfalfa hay to the receiving ration for the first 14 d. Calves assigned +IMMUN received a DNA immunostimulant on d 0. On d 0, 14, and 28, BW, rectal temperatures, and venous blood were collected. Health was recorded throughout the 56-d study, and pen weights on d 56. No HAY × IMMUN interactions occurred (P ≥ 0.18). During the first 14 d, calf ADG was greater (P < 0.01) for +HAY than-HAY, but d 14 to 28 ADG was lower (P < 0.01) for +HAY than-HAY. Calf ADG was lower (P ≤ 0.01) for +IMMUN than –IMMUN from d 28 to 56 and from d 0 to 56. Total DMI was greater (P < 0.01) for +HAY than –HAY from d 0 to 14, but lower (P ≤ 0.04) from d 14 to 28 and from d 28 to 56. Gain efficiency of +HAY calves was greater (less negative; P < 0.01) from d 0 to 14, but lower (P < 0.01) from d 14 to 28 when compared with –HAY. Gain efficiency was lower (P ≤ 0.02) for +IMMUN than –IMMUN calves from d 28 to 56 and d 0 to 56. Calf morbidity, mortality, and blood parameters (pH, glucose, lactate, hemoglobin saturated with oxygen [sO2]) were not affected (P ≥ 0.18) by treatments. Blood sO2 was lower (P < 0.01) on d 0 than d 14 and 28, and glucose was greater (P < 0.01) on d 28 than d 0 and 14. Blood sO2 correlated (P < 0.05) with glucose (R2 = 0.09), lactate (R2 = –0.12), and mortality (R2 = 0.08). Glucose correlated with lactate (R2 = 0.61), and first (R2 = –0.22) and second (R2 = –0.13) medical treatment. Lactate correlated (P < 0.05) with first medical treatment (R2 = –0.12) and mortality (R2 = –0.12). In conclusion, hay supplementation and immune stimulation did not affect calf health, performance, or blood gas parameters. Changes in calf health can be observed in measures of blood parameters.

The quality of steam-flaked corn (SFC) in feedlot diets can affect animal performance and the incidence of digestive disorders. Therefore, this study was conducted to define important and relevant measures used to determine SFC quality in commercial feedyards. Commercial feedlots (n = 17) located in Kansas, Nebraska, Texas, New Mexico, Arizona, and California were asked to participate in a survey to evaluate SFC manufacturing practices implemented, equipment used, and parameters targeted to measure flake quality. Manufacturing practice parameters evaluated included dry corn moisture, grain water addition, tempering time, steaming time, steam-cabinet temperature, mill electrical load, steam-conditioned corn moisture content, SFC moisture content, and SFC flake thickness. Equipment evaluated included roll size and steam-cabinet dimensions and capacity; flake quality parameters evaluated included hot and cooled SFC flake density, SFC volumetric flake weight, and starch availability of SFC samples. Samples of steam-conditioned corn and SFC were collected from each flaker (n = 49) within each feedlot. Flake density was measured on hot (immediately from below the rolls) and cooled flakes, and volumetric weight was measured only on cooled flakes. Steam-flaked corn samples were evaluated for starch availability using enzymatic hydrolysis. Enzymatic starch availability (ENZ) averaged 50.6 ± 8.02, with a range of 37.0 to 65.0%. Significant (P < 0.10) variables contributing to the final multiple linear regression model using ENZ as the dependent variable were SFC moisture, cooled flake density (CFD), and roll diameter [ENZ = 119.72 − (1.22 × SFC moisture) − (2.42 × CFD) + (0.47 × roll diameter); R2 = 0.5276; P < 0.10].

Published literature was reviewed to provide an overview of the historical prevalence and methods of controlling liver abscesses (LA) in feedlot cattle. Liver abscesses are typically categorized as mild, moderate, or severe, with severe LA most often being associated with reductions in performance. The prevalence of LA in beef-breed steers increased by 25% between 2008 and 2013; however, the prevalence in Holstein steers tripled over the same period. Regionally, the greatest prevalence has been observed in Kansas, eastern Colorado, and western Nebraska, and the lowest prevalence has been observed in the Midwest and the desert southwest. Fusobacterium necrophorum and Trueperella pyogenes are most commonly associated with LA, although F. necrophorum is likely the primary causative pathogen. Liver abscesses are often, but not always, associated with perforations in the rumen wall. Tylosin phosphate is commonly fed to control LA. Feeding elevated levels of roughage during growing and finishing periods results in a dramatic reduction in LA; overprocessing of dietary roughage reduces its effectiveness. Grain processing has marked effects on ruminal starch availability but has minimal effect on LA; inclusion of fibrous by-product feeds also does not mitigate prevalence of LA. Vaccination against F. necrophorum has shown little benefit in field application. Providing a source of true scratch-factor to the rumen, either by increasing the percentage of coarse roughage included in the TMR or by periodically providing coarse hay apart from the TMR, appears to be the most effective method of reducing LA.

Roughage plays a vital role in ruminant diets. This review considered the effects of roughage in diets for newly received cattle, the physical and physiological effects of roughage in feedlot cattle diets, the use of NDF as a means of assessing the roughage value for feedlot cattle, and potential alternatives to traditional roughages and roughage feeding practices. In newly received, stressed cattle, a meta-analysis from trials conducted at a single location indicated that receiving period morbidity (percentage of cattle pulled and treated for bovine respiratory disease) decreased slightly as roughage level increased. Nonetheless, increasing roughage level decreased receiving period ADG and G:F; therefore, unless cattle are able to compensate at later stages of the feeding period, the small decrease in morbidity with added roughage might be offset by decreased performance. For growing-finishing cattle, a meta-analysis indicated that intakes of DM and NEg increased linearly as dietary NDF concentration increased over a range of approximately 7.5 to 35% NDF. Both roughage and total dietary NDF were effective for determining the relative value of different roughage sources to achieve equal DMI in beef feedlot diets. Fiber in by-product feeds, such as wet corn gluten feed and distillers grains, dilute grain starch and might have the ability to substitute, in part, for traditional roughage; however, NDF concentration of these by-products is not an effective measure of roughage equivalency. Altering methods of roughage delivery, such as feeding a lower level of dietary roughage with intermittent delivery of additional dietary roughage or coarser forms of roughages that stimulate chewing or alter digesta passage rate, might provide a means of decreasing overall roughage use without compromising animal health and performance, but research is needed to test the merits of these approaches. Significant research questions remain to be addressed before we fully understand the chemical, physiological, and physical roles of roughage in feedlot diets.

Bovine Respiratory Disease (BRD) continues to be one of the major health concerns in the cattle industry. It is a multifactorial disease typically caused by infection of immune-compromised calves with both viral and bacterial pathogens. The purpose of this study was to compare the metaphylactic efficacy of various antimicrobials in high-risk beef calves.

Feedlot performance is negatively affected by the onset of infection and disease. The role of receiving calf diet composition in the development of clinical disease is debatable. This study was conducted to compare the effects of a low-concentrate diet with those of a high concentrate diet on the performance and health of newly received heifer calves.

Effects of ionophore type and carrier on in vitro ruminal digestion and fermentation patterns of a concentrate substrate were evaluated at various incubation times. Treatments were: control (no ionophore); lasalocid sodium commercial premix (Bov); lasalocid sodium mycelium cake (LasBio); laidlomycin sodium salt (LaidNa); laidlomycin propionate commercial premix (LaidPro); monensin sodium salt (Mon); and monensin sodium commercial premix (Rum). The Bov, LasBio, Mon, and Rum treatments supplied 4μg of ionophore/mL of culture volume, whereas the LaidNa and LaidPro treatments supplied 1.33μg of ionophore/mL. Total gas and methane production did not differ among treatments at any of the incubation times (P>0.09). Similarly, in vitro dry matter disappearance (IVDMD) was not affected by treatment (P>0.28) at 6, 18, and 24h of incubation; however, IVDMD (P=0.03) was greater for ionophores than for the control at 12h of incubation. Molar proportions of acetate (P<0.01), acetate:propionate (P<0.01), and total volatile fatty acid (VFA) concentrations (P<0.01) were decreased and propionate was increased (P<0.001) for the average of all ionophore-containing substrates compared with the control. Total VFA were decreased by Bov, LaidNa, and Rum, contrasted with their specific counterparts (LasBio, LaidPro, and Mon, respectively; P<0.05). Differences were detected among ionophore types for acetate (lasalocid vs. laidlomycin; P<0.05), propionate (lasalocid vs. monensin; P<0.05), and butyrate (monensin vs. lasalocid or laidlomycin; P<0.05). Capture of metabolic hydrogen in end products of fermentation was greater for ionophore-containing treatments (P<0.01) than for the control. These data suggest limited unique effects of ionophore type or carrier on IVDMD, total gas production, and methane; however, VFA proportions varied among ionophore types and carriers, which deserves further study.

Sixteen crossbred (British x Continental; average un-shrunk body weight = 507.9 kg; SD = 45.6 kg) beef heifers fed a steam-flaked corn-based finishing diet with melengestrol acetate (0.4 mg/heifer daily) included to suppress estrus were used in a completely random design to evaluate the efficacy of buccal administration of 0, 10, 100, or 1000 mg of 25-hydroxyvitamin D3, (25-OH D3). Serum Ca, P, Mg, 25-OH D3, 1,25-dihydroxyvitamin D [1,25-(OH)2 D3], albumin, and protein were measured 24 h before dosing (-24 h), at dosing (0 h), and 6 and 24 h after dosing, after which the cattle were slaughtered at a commercial facility. Samples of kidneys, liver, longissimus lumborum, and triceps brachii were collected and evaluated for concentrations of 1,25-(OH)2 D3. With -24 and 0 h as baseline covariates, a significant time x treatment interaction was observed for serum 25-OH D3 and Ca concentrations, but not for serum 1,25-(OH)2 D3. Supplemental 25-OH D3 doses of 100 and 1000 mg significantly increased serum 25-OH D3 at 24 h after dosing, 1,25-(OH)2 D3 at 6 and 24 h after dosing, and serum Ca at 24 h after dosing. Similarly, buccal dosing of 1000 mg of supplemental 25-OH D3 significantly increased (approximately 2- to 3-fold) concentrations of 1,25-(OH)2 D3 in the kidney, liver, and longissimus lumborum relative to the other 3 treatments but not in triceps brachii. Serum albumin, protein, P, and Mg were not affected by treatment. Based on these results, buccal administration of 100 and 1000 mg 25-OH D3 increased vitamin D3 metabolites in serum and tissues, and it should be an effective method of delivering the vitamin.

The objective of this study was to use feeding behavior of newly received steers (average initial weight 191 kg) to detect morbidity in animals in a commercial feedlot. Two separate 32 d feeding trials were conducted in Wellton, Arizona, in July and November 1996. Radio frequency technology was used to record the total time spent within 50 cm of the feedbunk (animal presence every 5.25 s times 5.25 s) in 3 h intervals from 0600 to 2400 on a daily basis for 103 and 122 male calves in trial 1 and 2, respectively. Statistical procedures based on the cumulative sums (CUSUM) of the 3 h feeding intervals were used to detect morbid animals, compared with detection of animals deemed morbid by experienced pen riders. In trial 1, the CUSUM procedure detected animal morbidity 4.5 d earlier (P < 0.001) than the feedlot personnel. In trial 2, the CUSUM procedure detected animal morbidity 3.7 d earlier (P < 0.001) than feedlot pen riders. Overall accuracy, positive predictive value and sensitivity of the CUSUM prediction method were 87, 91, and 90%, respectively. Combined trial data suggest that feeding behavior during the first 30 d cattle are in a receiving pen, as collected with radio frequency technology and analyzed with CUSUM charts, may be used to detect animal morbidity approximately 4.1 d earlier (P < 0.001) than conventional methods typically employed in commercial feedlots. Key words: Feeding behavior, morbidity, quality control, feedlots

Three 21-d trials were conducted at a commercial feedlot near Wellton, Arizona to determine the effects of metaphylactic injectable antibiotics on feeding and watering behavior and on animal health and growth performance of feedlot calves. Newly received male calves (n = 150, 150, and 148 for Trials 1, 2, and 3, respectively) were randomly assigned to one of four treatments: 1) no injectable antibiotic (control), 2) tilmicosin (TIL) subcutaneously (s.c.) 3) florfenicol i.m. (FIM), or 4) florfenicol s.c. (FSC). Throughout the 21-d trials, calves were observed and documented as morbid or healthy. Daily feeding and watering behaviors were collected for trials 2 and 3. A smaller (P=0.001) percentage of TIL, FIM, and FSC calves were identified as morbid (average, 27%) compared with control calves (47%), and ADG was greater (P=0.04) for TIL, FIM, and FSC calves (average, 0.42 kg/d) than for control calves (0.23 kg/d). Calves castrated before arrival had greater (P=0.001) ADG (0.53 vs 0.21 kg/d) and lower (P=0.05) mortality (0 vs 3.5%) during the first 21 d than did calves castrated upon arrival at the feedlot. Calves that remained healthy had greater (P=0.001) ADG than did calves that became morbid (0.78 vs−0.03 kg/d). Calves treated with TIL, FIM, or FSC had increased (P=0.02) feeding bouts per day in Trial 3 compared with control calves (average, 11 vs 9 bouts/d). Total feeding time was increased (P=0.005) for FIM calves compared with control, TIL, and FSC calves in Trial 3. No differences (P>0.10) were observed in watering behavior because of antibiotic treatment. Metaphylactic injectable antibiotics administered upon calves’ arrival at the feedlot did not reduce the total time newly received feedlot calves spent feeding, decreased the incidence of morbidity by 43%, and improved growth performance during the 21-d receiving period.