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Raising young dairy calves presents many challenges for producers and veterinarians including losses attributable to BRD. This article will discuss several key concepts for practitioners to consider when applying evidence-based medicine for the control and treatment of BRD in young dairy calves. The authors review BRD complex, provide considerations for diagnostic approaches, and discuss research associated with the control and treatment of BRD., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Changes in cattle feeding in the twentieth century led to the "Golden Age of Cattle Feeding" on the US High Plains; this was accompanied by recognition that bovine respiratory disease (BRD) is the leading cause of feedlot morbidity and mortality. Decades of research have illuminated the multiple viruses and bacteria that contribute to BRD, which led to vaccines and antimicrobials to prevent, treat, and control BRD. Despite these discoveries, feedlot BRD morbidities do not appear to have changed substantially over this time. New technologies are being developed that have the potential to improve accuracy of BRD detection., Competing Interests: Disclosure The authors have received financial support from veterinary biologics and pharmaceutical manufacturers for consulting and to conduct research to test the efficacy of products for BRD treatment, prevention, and control. Dr D.L. Step is employed by Boehringer Ingelheim Animal Health, a company that markets vaccines and antimicrobials for prevention, treatment, and control of BRD., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Bovine viral diarrhea virus (BVDV) represents a major cattle disease with multiple forms including fetal infections resulting in persistently infected (PI) cattle. The objectives of this study were to investigate the immune response to six vaccines, five modified live viral (MLV) and one killed vaccine containing BVDV immunogens as measured by antibodies to BVDV1a, BVDV1b, BVDV2a, and BVDV2c. The predominant BVDV subgenotype in the U.S. is BVDV1b compared to BVDV1a and BVDV2a. There are MLV and killed BVDV vaccines containing BVDV1a and BVDV2a marketed in the U.S. A prior study evaluated immune response to vaccination with BVDV1a and BVDV2a inducing virus neutralizing antibody titers. BVDV1b titers 128 or higher at time of exposure to BVDV1b PI cattle protected heifers against fetal infection. Calves received two doses and postweaning serums were collected and assayed for BVDV antibodies. Antibody titers were expressed as geometric mean averages. Percentages were expressed as proportions of animals within three antibody levels, including targeted level 128 or greater. There were statistical differences among vaccines in each study, particularly to BVDV1a, BVDV1b, and BVDV2a. MLV vaccines containing Singer strain induced higher levels to BVDV1a and BVDV1b than NADL vaccine in all three studies. Two vaccines, both MLV, Vaccine 1 and Vaccine 6 containing Singer strain induced higher proportion of 128 or higher BVDV1b titers than vaccine with NADL. Antibody levels to BVDV2a and BVDV2c were dependent on BVDV2a vaccine strain. This study indicates strain in BVDV vaccines reflects differences in immune response to different BVDV subgenotypes, particularly BVDV1b and BVDV2c., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Growth-promoting technologies such as implants, ionophores, and β-agonists improve feedlot performance, efficiency, and carcass characteristics of cattle. The objective of this experiment was to determine the effects of dose and duration of ractopamine hydrochloride (RH) on feedlot performance and carcass characteristics when fed to Holstein steers. A randomized complete block design was used with a 3 × 3 factorial arrangement of treatments with 3 RH doses (0, 300, or 400 mg∙steer -1 ∙d -1 ) fed for 3 durations (28, 35, or 42 d). Holstein steers ( n = 855; initial body weight [BW] = 448 ± 37 kg) were blocked by BW and randomly allocated to 1 of 9 pens (15 blocks; 9 dose × duration treatment combinations) approximately 72 d before harvest. Weekly pen weights, chute temperament scores, and animal mobility were determined during the RH feeding period. At harvest, carcass data were collected on all steers, and tenderness was measured on steaks from 3 or 4 randomly selected steers from each pen and slice shear force (SSF) was determined on one steak selected from each side of the carcass after aging for 14 or 21 d. For feedlot performance, carcass characteristics, and SSF, no dose × duration interactions were observed ( P ≥ 0.11). With increasing RH dose, average daily gain (ADG) and gain-to-feed ratio (G:F) increased linearly ( P ≤ 0.01), whereas BW gain increased linearly with RH dose and duration ( P ≤ 0.01). Hot carcass weight ( P = 0.02) and longissimus muscle (LM) area ( P ≤ 0.01) increased linearly with increasing RH dose. The percentage of carcasses in the USDA Yield Grade 2 category increased linearly ( P ≤ 0.01) and percentage of carcasses in the USDA Yield Grade 4 category tended ( P = 0.08) to decrease linearly as RH dose increased. In the 14-d aged steaks, the percentage of steaks with SSF ≤ 15.3 kg decreased linearly ( P ≤ 0.01), whereas the percentage of steaks with ≥20.0 kg SSF increased linearly ( P ≤ 0.01) with increasing RH dose. After 21-d aging, there was a tendency ( P = 0.06) for a greater percentage of steaks from steers fed RH to have SSF ≥ 20.0 kg (2% of total steaks), but no difference ( P ≥ 0.12) in the percentage of steaks with SSF ≤ 19.9 kg. Final chute temperament ( P ≥ 0.45) and animal mobility ( P ≥ 0.67) scores were not affected by feeding RH. Increasing the dose of RH (300 or 400 mg∙steer -1 ∙d -1 ) fed for 28 to 42 d before harvest increased ADG, G:F, hot carcass weight, and LM area when fed to Holstein steers with no negative effects on behavior or mobility. The percentage of steaks classified as not tender improved when steaks were aged for 21 d from steers treated with RH., (© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Morbidity and mortality in newly weaned calves resulting from bovine respiratory disease (BRD) continue to be the most significant problems facing the beef industry. Morbidity attributed to BRD accounts for approximately 75% of total feedlot morbidity. Several experiments have documented the economic impacts of BRD. Direct costs attributable to BRD include death loss, treatment and labor costs, and prevention costs, while indirect costs associated with BRD include decreased growth performance and feed efficiency, increased days on feed, and decreased carcass merit and market value. In recent years, cattle treated for BRD have returned $50 to $250 less per head at harvest than cattle never treated for BRD. Best management practices for newly weaned calves vary depending on a multitude of factors including: season of year calves are purchased, calf genetics, length of time in the marketing and transport channels, previous management and vaccination programs, and other factors. In general, calves purchased directly from a ranch have fewer health problems than calves purchased through auction markets. The longer a calf is in the marketing chain, the more likely health problems will be encountered. Calves that have spent several days in the marketing chain may develop clinical BRD before or very soon after arrival, whereas cattle with less time in the marketing chain may get sick later (2 to 4 wk), due to the length of time it takes for BRD to develop. On or before arrival, calves should be given a risk score (high, medium, or low) that relates to the quantity and magnitude of stress they have encountered and the probability they will develop BRD. High-risk calves typically will have been recently weaned, received no vaccinations, not been castrated or dehorned, been commingled, and moved through an auction market. Low-risk calves will often originate from a single source and will have gone through a preconditioning program that includes vaccination, castration, dehorning, weaning, and potentially feed bunk adaptation. Variation exists within risk category, so the preliminary assessment should be combined with visual observation on arrival as additional health assessments and feed intake information becomes available. Cattle managers should adjust management strategies based on risk category to meet the perceived needs of individual lots of cattle to improve the health and well-being of newly weaned calves.

Bovine respiratory disease (BRD) is responsible for the majority of morbidity, mortality, and production losses occurring in feedlots. This experiment evaluated the effects of BRD incidence on subsequent finishing performance, efficiency, carcass characteristics, and lung scores of steers. Crossbred steers (n = 516) were monitored daily for clinical signs of BRD (BRD attributed morbidity and mortality were 66.5 and 13.2%, respectively). A subset of calves (n = 174) were grouped by the number of times treated for BRD (BRDX) and randomly allocated to finishing pens. The BRDX experimental groups included never treated for BRD (0X; 8 pens) and treated 1 time (1X; 8 pens), 2 times (2X; 8 pens), or 3 or 4 times (3/4X; 8 pens). Arrival BW was not different among BRDX groups ( P = 0.17); however, BRDX during the receiving period decreased performance, resulting in BW of 324, 316, 285, and 260 kg for 0X, 1X, 2X, and 3/4X, respectively, at the start of finishing ( P < 0.001). Ultrasound estimates, BW, and visual appraisal were used to target a common body composition (average days on feed = 182). With increasing BRDX, days on feed increased linearly ( P = 0.002), whereas HCW, DP, rib eye area, QG, and unconsolidated lungs decreased linearly ( P ≤ 0.03). These results suggest that with additional days on feed, calves treated multiple times for BRD are able to reach similar compositional endpoints as their untreated cohorts; however, it may not be possible for these calves to reach the same QG and carcass yield., (© 2017 American Registry of Professional Animal Scientists.)

Bovine respiratory disease (BRD) is the most common and economically detrimental disease of beef cattle during the postweaning period, causing the majority of morbidity and mortality in feedlots. The pathogenesis of this disease often includes an initial viral infection, which can predispose cattle to a secondary bacterial infection. The objective of this experiment was to determine the effects of timing of an intratracheal (MH) challenge relative to 72 h of natural exposure to bovine viral diarrhea virus (BVDV) type 1b persistently infected (PI) calves on performance, serum antibody production, total and differential white blood cell (WBC) count, rectal temperature, clinical severity score (CS), and haptoglobin (Hp). Steers ( = 24; 276 ± 31 kg initial BW) were randomly allocated to 1 of 3 treatments (8 steers/treatment) in a randomized complete block design. Treatments were steers not exposed to calves PI with BVDV 1b and not challenged with MH (CON), steers intratracheally challenged with MH 84 h after being exposed to calves PI with BVDV 1b for 72 h (LateCh), and steers intratracheally challenged with MH 12 h after being exposed to calves PI with BVDV 1b for 72 h (EarlyCh). Performance (ADG, DMI, and G:F) was decreased ( < 0.001) for both EarlyCh and LateCh from d 0 to 4. From d 5 to 17, LateCh appeared to compensate for this lost performance and demonstrated increased ADG ( = 0.01) and G:F ( = 0.01) compared with EarlyCh. Both EarlyCh and LateCh had decreased platelet counts ( < 0.001) compared with CON. Antibody concentrations of BVDV and MH were higher ( < 0.05) for both EarlyCh and LateCh compared with CON. Rectal temperature, CS, and Hp increased ( < 0.001) across time from h 4 to 48, h 4 to 36, and h 8 to 168, respectively. Within 24 h of MH challenge, WBC and neutrophil concentrations within the blood increased whereas lymphocyte concentrations decreased. The timing of BVDV exposure relative to a MH challenge appears to influence the CS and acute phase response associated with BRD. As typical beef cattle marketing channels allow for variation in the timing of respiratory pathogen exposure, understanding the physiological changes in morbid cattle will lead to improved management of BRD.

Research has indicated that trace mineral (TM) supplementation may alter immune function and reduce morbidity associated with bovine respiratory disease. The objective of this experiment was to determine the influence of dietary Cu, Mn, and Zn supplementation on the performance, clinical signs, and TM balance of calves following a bovine viral diarrhea virus (BVDV) and (MH) combination respiratory pathogen challenge. Steers ( = 16; 225 ± 20 kg BW) from a single ranch were processed, weaned, and randomly pairwise assigned to either the TM-supplemented (MIN) or the control (CON) experimental treatments. The MIN calves received an additional 150 mg of Cu, 130 mg of Mn, and 320 mg of Zn daily and the CON calves received the basal diet with no additional Cu, Mn, or Zn supplementation. The basal diet contained sufficient Mn and Zn but inadequate Cu based on published nutrient requirements. After 46 d on the experimental treatments, all calves were naturally exposed to a heifer persistently infected with BVDV type 1b for 4 d and then subsequently intratracheally challenged with MH. Data were analyzed using the GLIMMIX procedure of SAS with sampling time serving as a repeated measure and calf serving as the experimental unit. The respiratory challenge was validated via increased BVDV type 1b antibody concentrations, MH whole cell and leukotoxin antibody concentrations, rectal temperatures (TEMP), and subjective clinical severity scores (CS). Calf performance ( ≥ 0.48) was not affected by TM supplementation. Mineral supplementation also did not impact the CS or TEMP of calves ( ≥ 0.53). There was a treatment × time ( < 0.001) interaction observed for liver Cu concentrations. The concentrations of Cu, Mn, Zn, and Fe within the liver; Cu, Mn, and Zn within the muscle; and Cu, Zn, and Fe within the serum were all impacted by time ( ≤ 0.03). Calves receiving the MIN treatment had greater ( < 0.01) liver Cu and Mn concentrations compared with CON calves. In contrast, serum Cu and Fe concentrations were increased ( ≤ 0.05) in CON calves compared with MIN calves. Mineral supplementation did not impact TM concentrations within the muscle ( ≥ 0.38). The supplementation of Cu, Mn, and Zn can improve the Cu and Mn status within the liver and serum of calves in response to a BVDV and MH challenge. When Cu is supplemented to calves receiving a marginally Cu-deficient diet, Cu status within the body is significantly improved.

The inclusion of wet distillers grains plus solubles (WDGS) in feedlot diets has become a common practice in many regions of the United States due to the expanded production of byproducts and fluctuating corn prices related to ethanol production and other factors. In addition, societal concerns over the continued use of antimicrobials in agriculture production combined with an enhanced interest in disease and pathogen prevention in the food supply have led to an increased interest in use of direct-fed microbials (DFM) in growing and finishing cattle. Direct-fed microbials have been shown to improve ADG and feed efficiency, alter ruminal fermentation, and decrease fecal shedding of potential harmful pathogens in feedlot cattle in some experiments. The objective of this experiment was to evaluate the effects of WDGS inclusion with or without a DFM containing (1 × 10 cfu ∙ heifer ∙ d) combined with (1 × 10 cfu ∙ heifer ∙ d) on the performance, carcass characteristics, and O157:H7 shedding in feedlot heifers. In early August, 288 crossbred heifers (initial BW = 295 ± 28 kg) were assigned to 1 of 4 treatments (12 pens per treatment; 6 heifers per pen) in a randomized complete block design with a 2 × 2 factorial arrangement of treatments. Body weights and fecal grab samples were obtained at approximately 28-d intervals throughout the experiment. Across the feeding period, heifers fed 30% WDGS tended ( = 0.09) to have greater ADG and had greater carcass-adjusted ADG ( = 0.05) compared with heifers fed dry-rolled corn (DRC). Dry matter intake was not affected ( = 0.65) by diet, although carcass-adjusted G:F tended ( = 0.10) to be improved for heifers fed WDGS. Heifers fed 30% WDGS tended ( ≤ 0.10) to have greater fat thickness at the 12th rib, lower marbling scores, and higher yield grades. The inclusion of . combined with . in the diet had no effect ( > 0.10) on performance or carcass merit in the present experiment. The incidence of O157:H7 throughout the experiment was low, with only 18 positive samples across all sampling periods. Neither WDGS inclusion nor the inclusion of . combined with . in the diet had any effect ( > 0.10) on O157:H7 shedding in this experiment. Feeding 30% WDGS to feedlot heifers improved animal performance compared to the DRC-based control diet.

Ancillary therapy (ANC) is commonly provided in conjunction with an antimicrobial when treating calves for suspected bovine respiratory disease (BRD) in an attempt to improve the response to a suspected BRD challenge. The first experiment evaluated the effects of 3 ANC in combination with an antimicrobial in high-risk calves treated for BRD during a 56-d receiving period. Newly received crossbred steers (n = 516; initial BW = 217 ± 20 kg) were monitored by trained personnel for clinical signs of BRD. Calves that met antimicrobial treatment criteria (n = 320) were then randomly assigned to experimental ANC treatment (80 steers/experimental ANC treatment): intravenous flunixin meglumine injection (NSAID), intranasal viral vaccination (VACC), intramuscular vitamin C injection (VITC), or no ANC (NOAC). Animal served as the experimental unit for all variables except DMI and G:F (pen served as the experimental unit for DMI and G:F). Within calves treated 3 times for BRD, those receiving NOAC had lower (P < 0.01) clinical severity scores (severity scores ranged from 0 to 4 on the basis of observed clinical signs and severity) and heavier (P = 0.01) BW than those receiving NSAID, VACC, or VITC at the time of third treatment. Between the second and third BRD treatments, calves receiving NOAC had decreased (P < 0.01) daily BW loss (−0.13 kg ADG) compared with those receiving NSAID, VACC, or VITC (−1.30, −1.90, and −1.41 kg ADG, respectively). There were no differences in rectal temperature, combined mortalities and removals, or overall performance among the experimental ANC treatments. Overall, morbidity and mortality attributed to BRD across treatments were 66.5% and 13.2%, respectively. After the receiving period, a subset of calves (n = 126) were allocated to finishing pens to evaluate the effects ANC administration on finishing performance, carcass characteristics, and lung scores at harvest. Ultrasound estimates, BW, and visual appraisal were used to target a common physiological end point for each pen of calves. There were no differences among the experimental ANC observed during the finishing period (P ≥ 0.11). In summary, the use of NSAID, VACC, and VITC do not appear to positively impact clinical health and could potentially be detrimental to performance during the receiving period in high-risk calves receiving antimicrobial treatment for suspected BRD.

Bovine respiratory disease complex (BRDC) is the leading cause of morbidity and mortality in feedlot cattle. Significant inflammation and lesions are often observed in lungs of infected cattle. During acute inflammatory responses, histones contribute to mortality in rodents and humans and serum proteins can protect against histone-induced cytotoxicity. We hypothesized that cattle experiencing chronic or fatal cases of BRDC have reduced ability to protect against cytotoxic effects of histones. Serum samples were collected from 66 bull calves at the time of normal feedlot processing procedures. Animals were retrospectively assigned to groups consisting of calves never treated for BRDC (control [CONT]; n = 10), calves treated with antimicrobials once for BRDC (1T; n = 16), calves treated twice for BRDC (2T; n = 13), calves treated 3 times for BRDC (3T; n = 14), or calves treated 4 times for BRDC (4T; n = 13). Samples were also collected each time animals received antimicrobial treatment; animals within a group were further sorted by calves that recovered and calves that died to test histone cytotoxicity. Bovine kidney cells were cultured in duplicate in 96-well plates and exposed to 0 or 50 μg/mL of total histones for 18 h with 1% serum from each animal. Cell viability was assessed by the addition of resazurin for 6 h followed by fluorescent quantification. Fluorescent values from serum alone were subtracted from values obtained for histone treatment for each animal. Serum from CONT, 1T, and 2T at initial processing all exhibited a similar (P > 0.10) response to histone treatment with fluorescent values of -312 ± 557, -1,059 ± 441, and -975 ± 489, respectively. However, 3T and 4T demonstrated an impaired capacity (P < 0.05) to protect against histones (-2,778 ± 471 and -3,026 ± 489) at initial processing when compared to the other groups. When sorted by mortality within group, calves that were treated twice and recovered (-847 ± 331) demonstrated a greater (P < 0.05) protective capacity than calves that were treated twice and died (-2,264 ± 412), indicating that calves that contract BRDC and ultimately die might have reduced protective capacity against histone cytotoxicity. Results suggest that calves that require multiple treatments for BRDC have reduced ability to protect against cytotoxicity of histones. Understanding the primary mechanism responsible for protecting against histone cytotoxicity could lead to improved identification of animals susceptible to severe cases of BRDC, improved focus and use of available resources, or better treatments for severe cases of BRDC

Three hundred ninety five calves were purchased from sale barns and delivered to the Willard Sparks Beef Research Center. Nasal swabs were collected to determine if presence of Mannheimia haemolytica and Pasteurella multocida in the upper respiratory tract (URT) can facilitate diagnosis of bovine respiratory disease (BRD). Samples were collected at arrival and at treatment for BRD. Clinically healthy control calves were sampled at time of treatment of sick calves. M. haemolytica was more commonly isolated from calves at treatment than at time of arrival or from control calves. M. haemolytica was more common in calves requiring treatment than in those never treated. Need for treatment and number of treatments were negatively associated with average daily gain, supporting the accuracy of diagnosis. These results suggest that URT sampling, when combined with clinical diagnosis, may assist in providing greater diagnostic accuracy, improving ability to evaluate risk factors, interventions, and treatments., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The objectives of this study were to examine the effects of feedlot production systems with and without the use of a β-adrenergic agonist compared to an all-natural production program on feedlot performance and carcass characteristics. Crossbred beef steers ( = 336; initial BW = 379 ± 8 kg) were randomized to 1 of 3 treatments in a randomized complete block design (RCBD; 14 steers/pen; 8 pens/treatment). Treatments consisted of an all-natural treatment (NAT), a conventional treatment (CONV), and a conventional treatment with a β-agonist (CONV-Z). All treatments were fed the same basal diet with NAT cattle receiving no growth promoting technologies. The CONV and CONV-Z cattle were implanted with 40 mg of estradiol and 200 mg of trenbolone acetate (TBA) on d 0 and were fed 33 and 9 mg/kg of monensin and tylosin daily, respectively. The CONV-Z cattle were fed zilpaterol hydrochloride (ZH) at 6.76 mg/kg (90% DM basis) for the last 20 days on feed (DOF) There was no effect of treatment on DMI ( = 0.83); however, CONV-Z steers gained 3.8% faster (1.64 vs. 1.58 kg/d; < 0.01) and were 5.3% more efficient (0.160 vs. 0.152; < 0.01) than CONV steers, and CONV steers gained 32.8% faster (1.58 vs. 1.19 kg/d; < 0.01) and were 26.7% more efficient (0.152 vs. 0.120; < 0.01) than NAT steers. There was a 35.7% improvement in estimated carcass gain (1.29 vs. 0.95 kg/d; < 0.01) and a 32.6% improvement in carcass efficiency (0.126 vs. 0.095; < 0.01) for CONV-Z steers compared to NAT steers. Hot carcass weight was increased by 8 kg for CONV-Z steers compared to CONV steers (394 vs. 386 kg; = 0.05) and 46 kg compared to NAT steers (394 vs. 348 kg; < 0.01). Longissimus muscle area was increased by 3.6 cm for CONV-Z steers compared to CONV steers (92.29 vs. 88.67 cm; = 0.02) and 12.1 cm for CONV-Z steers compared to NAT steers (92.29 vs. 80.16 cm; < 0.01), resulting in a 9.6% unit increase in USDA yield grade (YG) 1 (15.14 vs. 5.52%; < 0.05) and a 21.6% unit reduction in USDA YG 3 for CONV-Z steers compared to CONV steers (30.70 vs. 52.32%; < 0.05). The CONV-Z steers had a lower marbling score compared to the other treatments (432; 0.01), resulting in an 11.7% unit increase (20.70 vs. 9.03%; < 0.05) in USDA Select carcasses compared to CONV steers. The results of this experiment show that CONV-Z and CONV production results in a significant improvement in feedlot performance and USDA YG compared to NAT.

The objective of this study was to evaluate conventional (CONV) and natural (NAT) beef production systems from annual pasture through finishing through grazing. Beef steers (n=180, initial BW=250±19 kg) were assigned randomly to 2 treatments in the pasture phase. Steers were implanted with 40 mg of trenbolone acetate (TBA), 8 mg estradiol, and 29 mg tylosin tartrate (CONV), or received no implant (NAT). Steers on the 2 treatments grazed wheat or cereal rye for 109 d. Conventional steers had an 18.5% improvement in ADG (1.22 vs. 1.03 kg/d, P<0.01) and a heavier final BW (385 vs. 366 kg, P<0.01) compared with NAT steers. Following the pasture phase, steers (n=160 steers, 5 steers/pen, 8 pens/treatment) were assigned to a 2×2 factorial in the feedlot phase. Production system (NAT vs. CONV) was maintained from the pasture phase, and the second factor was 7 vs. 12% low-quality roughage (DM basis, LOW vs. HIGH). During finishing, CONV steers were given 120 mg of TBA and 24 mg estradiol at processing, fed monensin and tylosin, and fed zilpaterol hydrochloride for the last 20 d of the experiment. There were no program×roughage level interactions (P>0.07). The CONV steers ate 6.9% more feed (11.8 vs. 11.0 kg/d, P<0.01), gained 28.4% faster (1.90 vs. 1.48 kg/d, P<0.01), and were 24.2% more efficient (0.164 vs. 0.132, P<0.01) compared with NAT steers. The LOW steers had greater G:F (0.153 vs. 0.144, P<0.01) compared with HIGH steers. There was a 28.3% improvement in estimated carcass weight gain (1.36 vs. 1.06 kg/d), 18.6% improvement in carcass efficiency (0.115 vs. 0.097, P<0.01), and 21.6% improvement (1.52 vs. 1.25 Mcal/kg, P<0.01) in calculated dietary NEg for CONV compared with NAT steers. Hot carcass weight was increased by 62 kg (424 vs. 362 kg, P<0.01) and LM area was increased by 16.9 cm2 (100.9 vs. 84.0 cm2, P<0.01), decreasing USDA yield grade (YG, 3.09 vs. 3.54, P<0.01) for CONV steers compared with NAT steers. Natural steers had a greater percentage of carcasses in the upper 2/3 of USDA Choice grade (48.7 vs. 18.7%, P<0.01), a greater percentage of YG 4 and 5 carcasses (25.4 vs. 9.3%, P<0.01), and a greater percentage of abscessed livers (39.6 vs. 10.5%, P<0.01) compared with CONV steers. The results show that CONV production results in more rapid and efficient production that resulted in heavier carcasses with superior YG and desirable quality grades with both roughage levels.

Bovine respiratory disease (BRD) involves interactions between respiratory pathogens and stressors. Marketing beef cattle in North America frequently involves commingling of cattle from different backgrounds along with various stressors. Veterinarians are faced with unique challenges when designing preventive health care protocols. Research at Oklahoma State University has generated information to assist the practitioner to make more informed recommendations regarding the value of a single vaccination or revaccination in high-risk cattle, and the benefits of management programs at the farm or ranch of origins, particularly in regard to the impact of commingling of cattle from different origins.

Objective: To evaluate whether pedal bacteremia develops following regional IV perfusion (RIVP) of a 2% lidocaine hydrochloride solution in cattle with deep digital sepsis (DDS) and to determine which bacterial pathogens are most commonly isolated from the pedal circulation., Design: Prospective observational cohort study., Animals: 9 adult cattle with DDS in 10 limbs and 10 healthy adult cattle with no evidence of lameness or digital infection., Procedures: Blood samples were obtained aseptically from the dorsal common digital vein immediately following tourniquet application and 30 to 60 minutes after aseptic RIVP with a 2% lidocaine solution. Aerobic and anaerobic bacterial cultures were performed on all samples collected. For cattle with DDS, clinical examination with or without debridement of digital lesions was performed after RIVP., Results: Bacteria were isolated from pedal blood prior to RIVP in 1 cow with DDS and after RIVP and examination with or without debridement in that cow and 4 additional cattle with DDS. Bacteria were not isolated from any blood sample obtained from the healthy cattle. Of the 8 bacterial isolates identified, 5 were gram-positive facultative anaerobes. Cattle with DDS were significantly more likely to develop bacteremia in the pedal circulation than were healthy cattle following RIVP., Conclusions and Clinical Relevance: Results indicated that bacteremia may be present in the pedal circulation before and following RIVP and examination with or without debridement in cattle with DDS. Thus, systemic or local antimicrobial treatment might be warranted prior to or concurrently with RIVP in cattle with DDS.

Inflammation caused by bovine respiratory disease (BRD) continues to be one of the greatest challenges facing beef cattle producers and feedlot managers. Inflammation decreases DMI, ADG, and G:F in feedlot calves, decreasing growth rate and increasing days on feed, which results in economic losses during the feeding period. During the past decade, marketing of feedlot animals has changed from selling cattle on a live basis to a grid-based marketing system. When cattle are marketed on a live basis, the economic effects of BRD stop at increased health cost and decreased feedlot performance, carcass weight, and death loss. However, when cattle are marketed in a grid-based system, inflammation has the potential to also affect carcass cutability and quality. The effects of inflammation on feedlot cattle in regards to performance are well understood; however, specific effects on cattle growth and ultimately carcass merit are not as well described. Recent studies in feedlot cattle have indicated that the incidence of BRD decreases both HCW and marbling; however, mechanisms are not understood. Research in other species has demonstrated that during the acute phase response, pro-inflammatory cytokines promote skeletal muscle catabolism to supply AA and energy substrates for immune tissues. Further, during this early immune response, the liver changes its metabolic priorities to the production of acute phase proteins for use in host defense. Together these dramatic shifts in systemic metabolism may explain the detrimental effects on performance and carcass traits commonly associated with BRD in feedlot calves. Moreover, recent studies relative to human health have revealed complex multilevel interactions between the metabolic and immune systems, and highlighted inflammation as being a significant contributor to major metabolic diseases. The objective of this paper is to review data to help explain the economical and physiological effects of inflammation on cattle growth and carcass merit.

The objective of this study was to assess the role of leukotoxin (LKT) in modulating the pulmonary cytokine response of calves challenged with Mannheimia haemolytica. Thirty-six calves, seronegative to LKT and M. haemolytica whole cell antigen were divided into three groups (I, II and III). Calves in groups I and II were challenged by the intra-bronchial route with 25 mL of phosphate buffered saline (PBS) containing 0.44×10(9) cfu/mL of LKT deficient (lkt(-)) and 25 mL of PBS containing 0.31×10(9) cfu/mL of wild-type (wt) M. haemolytica serotype 1, respectively. Group III calves were challenged intra-bronchially with 25 mL of sterile PBS. Leukocytes were collected from broncho-alveolar lavage fluid (BALF) 4 days before and at 1, 3, and 6 days post-inoculation (p.i.). Expression of the following cytokines in the recovered leukocytes was measured using real-time PCR: interleukin (IL)-1β, -8, -10, -12 (p40) and TNF-α. The amount of TNF-α produced was also quantified by ELISA. Although a statistically significant difference in the expression of these cytokines was not observed between groups challenged with the wt and lkt(-) strains, the wt infected group (II) did exhibit higher mean clinical scores. Overall, there was considerable variation in the composition of the BALF between the groups and by day 7 p.i., both lkt(-)- and wt-challenged calves had seroconverted to M. haemolytica., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Bovine respiratory disease complex is the leading cause of morbidity and mortality in feedlot cattle. A number of vaccines against bacterial respiratory pathogens are commercially available and researchers have studied their impact on morbidity, mortality, and other disease outcome measures in feedlot cattle. A systematic review will provide veterinarians with a rigorous and transparent evaluation of the published literature to estimate the extent of vaccine effect. Unfortunately, the published body of evidence does not provide a consistent estimate of the direction and magnitude of effectiveness in feedlot cattle vaccination against Mannheimia haemolytica, Pasteurella multocida, or Histophilus somni.

A retrospective study was performed to compare the treatment regimens in feedlot cattle that died with bovine respiratory disease (BRD) to the antimicrobial susceptibility patterns of the microorganisms isolated from lungs. Forty-three cattle submitted by the Willard Sparks Beef Research Center (WSBRC) to the Oklahoma Animal Disease Diagnostic Laboratory for postmortem examination during 2007 had bronchopneumonia (acute = 16, subacute = 5, or chronic = 22). Lungs from cattle were cultured aerobically (40 cattle) and for Mycoplasma spp. (34 cattle). Susceptibility panels were performed. At least 1 BRD pathogen (Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Mycoplasma bovis, or Arcanobacterium pyogenes) was isolated from 39 cattle, and 77% (30/39) had multiple organisms recovered. Mycoplasmal infections were common (25/34) and a major component of mixed infections (24/25). The majority (60%) of the M. haemolytica, P. multocida, and H. somni isolates were resistant to tetracycline. Most of the H. somni isolates (67%) were susceptible to tilmicosin (Ti), enrofloxacin (En), ceftiofur (Ce), and florfenicol, despite extensive treatment with Ti, En, and Ce (75% of isolates were from cattle that received each antimicrobial once). Most of the M. haemolytica (65%) and P. multocida (79%) isolates were susceptible to En and Ce, despite antemortem treatment of cattle with these antimicrobials. Hence, the current study reports a discrepancy between the antemortem treatment of clinical BRD and the susceptibility patterns of the bacteria isolated from lungs postmortem. Based on these findings, factors other than antimicrobial resistance are playing a role in the death of feedlot cattle with BRD.

Objective: To evaluate serum haptoglobin concentration at feedlot arrival and subsequent performance and morbidity and mortality rates of calves that developed bovine respiratory disease., Animals: 360 heifer calves and 416 steer and bull calves., Procedures: Serum samples were obtained from cattle at the time of arrival to a feedlot (day -1) and analyzed for haptoglobin concentration. In experiment 1, calves were classified into groups with a low (< 1.0 μg/mL), medium (1.0 to 3.0 μg/mL), or high (> 3.0 μg/mL) serum haptoglobin concentration and allotted into pens on the basis of group. In experiment 2, calves were classified as having or not having detectable serum haptoglobin concentrations., Results: In experiment 1, average daily gain from days 1 to 7 decreased as haptoglobin concentration increased. Dry-matter intake (DMI) from days 1 to 21 decreased with increasing haptoglobin concentration, and DMI typically decreased from days 1 to 63. Total bovine respiratory disease morbidity rate typically increased with increasing haptoglobin concentration. At harvest, no differences in carcass characteristics were observed on the basis of haptoglobin concentration. In experiment 2, cattle with measureable serum haptoglobin concentrations at arrival weighed less throughout the experiment, gained less from days 1 to 7, and had lower DMI from days 1 to 42. Overall morbidity rate was not different between groups, but cattle with detectable serum haptoglobin concentrations had higher odds of being treated 3 times., Conclusions and Clinical Relevance: Serum haptoglobin concentration in cattle at the time of feedlot arrival was not associated with overall performance but may have limited merit for making decisions regarding targeted prophylactic treatment.

This study investigated bovine coronavirus (BCV) in both beef calves direct from the ranch and commingled, mixed-source calves obtained from an auction market. The level of BCV-neutralizing antibodies found in the calves varied among ranches in 2 different studies in a retained-ownership program (ROP), from the ranch to the feedlot. Calves with low levels of BCV-neutralizing antibodies (16 or less) were more likely to be treated for bovine respiratory disease (BRD) than those with higher titers. In 3 studies of commingled, mixed-source calves, BCV was recovered from calves at entry to the feedlot and the infections were cleared by day 8. The BCV was identified in lung samples [bronchoalveolar lavage (BAL) collection] as well as in nasal swabs. Calves with low levels of BCV-neutralizing antibodies at entry were most likely to be shedding BCV. Bovine coronavirus was isolated from both healthy and sick calves, but not from sick calves after 4 d arrival at the feedlot. Bovine coronavirus (BCV) should be considered along with other bovine respiratory viruses in the diagnosis of etiologies in bovine respiratory disease, especially for animals that become sick shortly after arrival. If approved vaccines are developed, it would be best to carry out vaccination programs before calves are weaned, giving them sufficient time to gain active immunity before commingling with other cattle.

Mycoplasma bovis is a pathogen causing respiratory disease, otitis media, arthritis, mastitis, and a variety of other diseases in cattle worldwide. It is increasingly recognized by the veterinary and livestock communities as having an important impact on the health, welfare, and productivity of dairy and beef cattle. M. bovis diseases can be difficult to diagnose and control because of inconsistent disease expression and response to treatments and vaccines, and large gaps in our understanding of the epidemiology and pathophysiology of these diseases. There are limited data on which to base evidence-based decisions for treatment and control, and the literature contains differing clinical biases and opinions. This document is intended for veterinarians dealing with cattle and is focused on the cattle production systems of North America. The goal of the consensus statement panel was to encourage an evidence-based approach to M. bovis problems. The scientific literature was critically reviewed, including peer-reviewed journal articles and reviews obtained by database searches using the terms "Mycoplasma bovis" or "mycoplasma + cattle." Where other data were lacking, conference proceedings were reviewed as a source of expert opinion., (Copyright © 2011 by the American College of Veterinary Internal Medicine.)

Remote rumen temperature monitoring is a potential method for early disease detection in beef cattle. This experiment was conducted to determine if remotely monitored rumen temperature boluses could detect a temperature change in steers exposed to bovine viral diarrhea virus (BVDV) and challenged with a common bovine respiratory disease pathogen, Mannheimia haemolytica (MH). Twenty-four Angus crossbred steers (BW = 313 ± 31 kg) were allotted to 1 of 4 treatments: 1) no challenge (control); 2) challenge by a 72-h exposure to 2 steers persistently infected with BVDV; 3) bacterial challenge with MH; and 4) viral challenge by a 72-h exposure to 2 steers persistently infected with BVDV followed by bacterial challenge with MH (BVDV + MH). Remotely monitored rumen temperature boluses programmed to transmit temperature every minute were placed in the rumen before the time of exposure to steers persistently infected with BVDV. Rectal temperatures were taken before MH challenge (0) and at 2, 4, 6, 12, 18, 24, 36, 48, 72, and 96 h after MH challenge. Rumen temperatures were recorded 3 d before (-72 h; period of BVDV exposure) through 14 d after (336 h) MH challenge. Rumen temperatures were analyzed as a randomized complete block design with a 2 × 2 factorial arrangement of treatments and a first-order autoregressive covariance structure for repeated measures. A treatment × day interaction was observed for average daily rumen temperature (P < 0.01). A treatment difference (P < 0.01) was observed on d 0, when MH-challenged steers had greater rumen temperatures than steers not challenged with MH. There was no BVDV × day interaction (P > 0.01). Rumen temperatures averaged every 2 h resulted in a BVDV × hour interaction (P < 0.01) and an MH × hour interaction (P < 0.01). The BVDV × hour differences occurred at h -18 to -14, 40 to 46, 110, 122, and 144 to 146 (P < 0.01). The MH × hour difference occurred at h 4 to 24 (P < 0.01). Maximum rumen temperature was increased (P < 0.01) for BVDV (0.8 °C), MH (1.2 °C), and BVDV + MH (1.3 °C) compared with the control. On average, rumen temperatures measured by the boluses at the same time points as the rectal temperatures were 0.13 °C less than rectal temperatures, and the 2 body temperatures were highly correlated (r = 0.89). Rumen temperature boluses appear to have potential as a tool for detecting temperature changes associated with adverse health events such as exposure to bovine respiratory disease and BVDV.

Objective: To determine efficacy of a modified-live virus (MLV) vaccine containing bovine viral diarrhea virus (BVDV) 1a and 2a against fetal infection in heifers exposed to cattle persistently infected (PI) with BVDV subtype 1 b., Animals: 50 heifers and their fetuses., Procedures: Susceptible heifers received a placebo vaccine administered IM or a vaccine containing MLV strains of BVDV1a and BVDV2a administered IM or SC. On day 124 (64 to 89 days of gestation), 50 pregnant heifers (20 vaccinated SC, 20 vaccinated IM, and 10 control heifers) were challenge exposed to 8 PI cattle. On days 207 to 209, fetuses were recovered from heifers and used for testing., Results: 2 control heifers aborted following challenge exposure; both fetuses were unavailable for testing. Eleven fetuses (8 control heifers and 1 IM and 2 SC vaccinates) were positive for BVDV via virus isolation (VI) and for BVDV antigen via immunohistochemical analysis in multiple tissues. Two additional fetuses from IM vaccinates were considered exposed to BVDV (one was seropositive for BVDV and the second was positive via VI in fetal tissues). A third fetus in the SC vaccinates was positive for BVDV via VI from serum alone. Vaccination against BVDV provided fetal protection in IM vaccinated (17/20) and SC vaccinated (17/20) heifers, but all control heifers (10/10) were considered infected., Conclusions and Clinical Relevance: 1 dose of a BVDV1a and 2a MLV vaccine administered SC or IM prior to breeding helped protect against fetal infection in pregnant heifers exposed to cattle PI with BVDV1b.

Bovine respiratory disease (BRD) is the most common and costly disease of beef cattle in North America. Despite extensive research, industry practices are often more informed by dogma than by fact. Frequently advocated interventions, including vaccination, various processing procedures, and nutritional manipulation, have limited impact on morbidity and mortality. Evidence for use of oral antimicrobials, either in feed or water, appears to be equivocal. In contrast, preconditioning and metaphylaxis have significant scientific evidence of efficacy, with weaning prior to sale potentially being the most important component of preconditioning. The inability to reach more definitive conclusions in preventing BRD may be attributable to difficulties in investigating the disease. Study challenges include potential for extensive confounding, tremendous variability, the multi-factorial nature of the disease, and inadequate methods for diagnosis.

Bovine respiratory disease (BRD) is the most costly disease of beef cattle in North America. It is multi-factorial, with a variety of physical and physiological stressors combining to predispose cattle to pneumonia. However, efforts to discern which factors are most important have frequently failed to establish definitive answers. Calves are at highest risk shortly after transport. Risk factors include purchasing from sale barns and commingling. It is unclear whether or not these practices increase susceptibility, increase exposure, or are proxies for poor management. Lighter-weight calves appear to be at greater risk, although this has not been consistent. Persistent infection (PI) with bovine virus diarrhea virus increases BRD occurrence, but it is unclear if PI calves affect other cattle in the feedlot. The complexity of BRD has made it difficult to define involvement of individual factors. Stressors may play a role as "necessary but not sufficient" components, requiring additive effects to cause disease.

Heifers with expected increased risk of bovine respiratory disease (BRD; n = 360; initial BW = 241.3 +/- 16.6 kg) were assembled at a Kentucky order-buyer facility and delivered to Stillwater, OK, in September 2007 to determine the effects of clinical BRD observed during preconditioning on subsequent feedlot performance, carcass characteristics, and meat attributes. During a 63-d preconditioning period, morbidity and mortality attributed to BRD were 57.6 and 8.6%, respectively. Immediately after preconditioning, heifers were grouped according to health outcome category and allotted to finishing pens (5 to 7 heifers/pen). Heifers were never treated for BRD (0X; n = 9 pens), treated 1 time (1X; n = 9 pens), 2 times (2X; n = 6 pens), 3 times (3X; n = 6 pens), or designated as chronically ill (CI; n = 2 pens). Arrival BW was not different (P = 0.21) among treatment categories. However, disease incidence during preconditioning decreased (P < 0.001) growth, resulting in BW of 318, 305, 294, 273, and 243 kg for 0X, 1X, 2X, 3X, and CI, respectively, at the start of the finishing phase. Estimates on the LM, taken by ultrasound on d 65 and 122, were combined with BW and visual appraisal to target common average endpoint within category and block. On average, heifers were slaughtered on d 163 for 0X, 1X, and 2X, d 182 for 3X, and d 189 for CI (P < 0.01). Final BW was similar (P > or = 0.18) for heifers treated 0, 1, 2, or 3 times, but heifers deemed CI weighed less (P = 0.01) than 3X heifers. Considering the finishing phase only, ADG was linearly increased (P < 0.001) with increasing BRD treatments, but was linearly decreased (P = 0.003) as BRD treatments increased from arrival to slaughter. Therefore, G:F was greater (P = 0.007) for CI than 3X and linearly increased (P = 0.002) from 0X to 3X. Similar to BW, HCW was less (P = 0.03) for CI than 3X. Marbling score tended (P = 0.06) to decrease linearly as the number of treatments increased, but no other differences (P > or = 0.24) in carcass traits were detected. No differences were observed in beef tenderness (P = 0.65), and no consistent trends were noted in retail display or palatability data. Less than 20 additional days on feed were required for heifers treated 3 times to have similar BW and carcass characteristics to heifers never treated for BRD. Segregating animals with multiple BRD treatments and feeding them to an acceptable carcass endpoint may be a viable strategy for increasing value of animals treated for BRD.

Bovine viral diarrhea viruses (BVDV) have been isolated alone or in combination with other viral and bacterial pathogens in animals diagnosed with bovine respiratory disease (BRD), a disease causing major economic loss to the feedlot industry. The objective of this experiment was to determine the effects of Mannheimia haemolytica challenge after short-term exposure (72 h) to bovine viral diarrhea virus type 1b (BVDV1b) persistently infected (PI) calves on performance, N balance, and organ mass in finishing cattle. Treatments (6 steers/treatment; initial BW = 314 +/- 31 kg) were 1) steers not exposed to steers PI with BVDV nor challenged with M. haemolytica (control; CON); 2) steers exposed to 2 steers PI with BVDV1b (BVD) for 72 h; 3) steers intratracheally challenged with M. haemolytica (MH); or 4) steers exposed to 2 steers PI with BVDV1b for 72 h and challenged with M. haemolytica (BVD+MH). There were 12 h between exposure to PI steers and challenge with M. haemolytica. Steers were housed in metabolism stanchions during the first 5 d after the M. haemolytica challenge and on d 7 to 11, 28 to 32, and for 5 d before slaughter (average 119 d on feed) to determine N balance and were weighed every 28 d. At slaughter, carcass and organ mass data were collected. Data were analyzed as a randomized complete block design with a 2 x 2 factorial arrangement of treatments, and steer was used as the experimental unit. From d -3 (beginning of PI steer exposure) to 4, steers challenged with M. haemolytica had less (P = 0.04) ADG than steers not challenged with M. haemolytica. In addition, steers exposed to steers PI with BVDV tended (P = 0.09) to have less ADG and G:F across the entire finishing period than steers not exposed to BVDV. Before slaughter, retained N expressed as grams per day (P = 0.03) and as a percentage of N intake (P = 0.04) was less in BVD steers compared with steers not exposed to BVDV. There were no effects (P > 0.10) of BVDV exposure or M. haemolytica challenge on empty BW (EBW) or carcass characteristics. Expressed as a percentage of EBW, HCW was less (P = 0.02) and total offal weight was greater (P = 0.02) for steers challenged with M. haemolytica compared with steers not challenged. Results are in agreement with those reported in larger scale finishing studies and suggest that acute exposure to BRD-related pathogens can have long-term effects on animal performance.

The objective was to determine effects of an intratracheal Mannheimia haemolytica challenge after 72-h exposure to bovine viral diarrhea virus type 1b (BVDV1b) persistently infected (PI) calves on serum antibody production, white blood cell count (WBC), cytokine concentrations, and blood gases in feedlot steers. Twenty-four steers (initial BW = 314 +/- 31 kg) were randomly allocated to 1 of 4 treatments (6 steers/treatment) arranged as a 2 x 2 factorial. Treatments were 1) steers not exposed to steers PI with BVDV nor challenged with M. haemolytica (control; CON); 2) steers exposed to 2 steers PI with BVDV for 72 h (BVD); 3) steers intratracheally challenged with M. haemolytica (MH); and 4) steers exposed to 2 steers PI with BVDV for 72 h and challenged with M. haemolytica (BVD+MH). There were 12 h between exposure to PI steers and challenge with M. haemolytica. Rectal temperature was increased (P < 0.001) for MH and BVD+MH during the initial 24 h after the M. haemolytica challenge. For MH and BVD+MH, total WBC count was increased (P < 0.01) at 36 h post M. haemolytica challenge compared with CON, whereas in BVD steers, WBC count was decreased (P < 0.01). Total lymphocyte count was increased (P = 0.004) during the initial 72 h post BVDV exposure for the BVD and BVD+MH groups compared with MH and CON, and this difference remained at 96 h post M. haemolytica challenge. An increased (P < 0.001) total neutrophil count was observed during the initial 36 h for the MH group and at 72 h for the BVD+MH challenge group. Interleukin 1beta, IL-6, and tumor necrosis factor alpha (TNFalpha) concentrations were greater (P

The lone star tick, Amblyomma americanum, vectors pathogens of emerging diseases of humans and animals in the United States. Currently, measures are not available for effective control of A. americanum infestations. Development of vaccines directed against tick proteins may reduce tick infestations and the transmission of tick-borne pathogens. However, the limiting step in tick vaccine development has been the identification of tick protective antigens. Herein, we report the application of RNA interference (RNAi) for screening an A. americanum cDNA library for discovery of tick protective antigens that reduce tick survival and weights after feeding. Four cDNA clones, encoding for putative threonyl-tRNA synthetase (2C9), 60S ribosomal proteins L13a (2D10) and L13e (2B7), and interphase cytoplasm foci protein 45 (2G7), were selected for vaccine studies in cattle, along with subolesin, a tick protective protein identified previously. In vaccinated cattle, an overall efficacy (E)>30% was obtained when considering the vaccine effect on both nymphs and adults, but only 2D10, 2G7 and subolesin affected both tick stages. The highest efficacy of control for adult ticks (E>55%) was obtained in cattle vaccinated with recombinant 2G7 or subolesin. These collective results demonstrated the feasibility of developing vaccines for the control of lone star tick infestations. The use of RNAi for identification of tick protective antigens proved to be a rapid and cost-effective tool for discovery of candidate vaccine antigens, and this approach could likely be applied to other parasites of veterinary and medical importance., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

The objective was to evaluate the effects of an extended withdrawal period after feeding the beta-adrenergic agonist zilpaterol hydrochloride (ZH) for 20 d at the end of the feeding period. Three hundred eighty-four crossbred beef steers were blocked by BW and randomly allocated into 64 pens (6 steers/pen). Pens were assigned to treatments in a 2 x 4 factorial arrangement in a randomized complete block design. Main effects were the addition of 0 (control) or 8.3 mg/kg of ZH (DM basis) to the finishing diet for 20 d before estimated average slaughter date and paired withdrawal periods of 3, 10, 17, or 24 d before slaughter. Individual BW were measured initially, 1 d before ZH feeding, and 1 d before slaughter. The ZH feeding period was initiated so that control cattle in the 3-d withdrawal group would be expected to average 65% USDA Choice Quality grade and have 1.27 cm of 12th-rib fat based on visual appraisal. Carcass data were collected at slaughter. For the 3-d withdrawal steers, 2 steers from each pen were selected to determine visceral organ and total offal mass at slaughter. The ZH x withdrawal day interaction was not significant (P > 0.10) for the majority of variables. There was no difference (P > or = 0.12) due to ZH feeding for final BW, carcass-adjusted final BW, or ADG. However, DMI was decreased (P = 0.02) and G:F increased (P = 0.01) in steers fed ZH vs. control steers. As day after withdrawal of ZH increased, there was a linear increase (P < 0.001) in final BW and carcass-adjusted final BW, but a linear decrease (P < 0.001) in ADG over the finishing period and over the ZH plus withdrawal period. Overall, HCW was 380 and 369 kg (P < 0.001) for ZH and control steers, respectively. However, the difference between ZH and control was 14, 17, 5, and 6 kg with 3, 10, 17, and 24 d withdrawal, respectively (ZH x withdrawal day, P = 0.09). Feeding ZH increased dressing percentage (65.8 vs. 64.6%; P < 0.001) and LM area (94.8 vs. 89.7 cm(2); P < 0.001), and decreased calculated yield grade (2.69 vs. 2.91; P = 0.03) and percentage of cattle grading USDA Choice (31.1 vs. 42.3%; P = 0.03) compared with controls. Small intestinal mass (g/kg of empty BW) was greater (P = 0.03) for steers fed ZH compared with controls. There were no other differences (P > or = 0.11) in mass of body components, expressed in kilograms or as a fraction of empty BW. In this experiment, improvements in animal performance and HCW due to feeding ZH were generally maintained when withdrawal was extended through 10 d.

This study was done to determine if intranasal vaccination of weaned beef calves with a chimeric protein containing the immunodominant surface epitope of Mannheimia haemolytica PlpE (R2) and the neutralizing epitope of leukotoxin (NLKT) covalently linked to truncated cholera toxin (CT) subunit B (CTB) could stimulate secretory and systemic antibodies against M. haemolytica while enhancing resistance of cattle against M. haemolytica intrabronchial challenge. Sixteen weaned beef calves were intranasally vaccinated with CTB-R2-NLKT chimeric (SAC102) or with R2-NLKT-R2-NLKT chimeric (SAC89) protein with or without native CT on days 0 and 14 and were challenged intrabronchially on day 28. In vitro, SAC102 bound the CT receptor molecule, GM(1)-ganglioside. Mean IgA antibodies to M. haemolytica whole cells (WC) and to LKT were high on day 0. A small, yet significant increase (p<0.05) was found in mean nasal antibodies to M. haemolytica WC for the SAC89+CT and SAC102 vaccinates after the second vaccination. SAC102 stimulated significant (p<0.05) mean serum antibody responses to all three antigens by day 28. Following challenge, mean antibodies to WC and LKT significantly increased (p<0.05) for the SAC102, SAC89 and SAC89+CT groups with the mean antibody responses to rPlpE stimulated by SAC102 vaccination being significantly higher (p<0.05) than for the other vaccinated and control groups. On day 1 after challenge, mean clinical score for the control group was significantly higher (p<0.05) than for the SAC102 and SAC89+CT vaccinates, and by day 2 after challenge, clinical score for the control group was significantly higher (p<0.05) than for all three chimeric vaccinated groups. Therefore, intranasal vaccination with CTB-R2-NLKT (SAC102) and R2-NLKT-R2-NLKT (SAC89) chimeric proteins enhanced resistance against intrabronchial challenge with the bacterium as well as stimulating antibody responses to M. haemolytica antigens.

Objective: To evaluate exhaled N(2)O (eN(2)O), exhaled CO (eCO), and serum haptoglobin concentrations as diagnostic criteria for bovine respiratory disease (BRD) and determine whether a combination of biomarkers would be useful for predicting health outcomes of heifer calves., Animals: 337 heifer calves newly arrived at a feedlot., Procedures: Body weights, serum haptoglobin concentrations, and rumen temperatures were determined. Calves (n = 183) were randomly selected for breath sampling. Variables were compared among calves that remained healthy and those requiring treatment., Results: Body weight at the time of first and second antimicrobial treatments did not differ from that at arrival, whereas body weight at the time of third antimicrobial treatment was lower. Temperature was lower at arrival, compared with that during antimicrobial treatment. Ratio of eN(2)O:eCO(2) was lowest at arrival, intermediate at the first and second antimicrobial treatments, and greatest at the third antimicrobial treatment. Ratio of eCO:eCO(2) was greater at times of antimicrobial treatment, compared with arrival. Concentration of serum haptoglobin was greatest at the time of the first antimicrobial treatment, lowest at the times of second and third treatments, and intermediate at arrival. Arrival ratios of eN(2)O: eCO(2) and eCO:eCO(2) and concentration of haptoglobin did not differ among heifers subsequently treated 1, 2, or 3 times., Conclusions and Clinical Relevance: Although breath analysis was successfully implemented in a research feedlot, arrival rumen temperature, eN(2)O, eCO, and haptoglobin concentration were not accurate in predicting occurrence of BRD during a preconditioning program. However, these biomarkers might support the diagnosis of BRD.

Objective-To compare effects of administration of a modified-live respiratory virus vaccine once with administration of the same vaccine twice on the health and performance of cattle. Design-Randomized, controlled trial. Animals-612 mixed-breed male cattle with unknown health histories. Procedures-Cattle were randomly assigned to 1 of 2 treatment groups (single vaccination treatment group [SVAC group] vs revaccination treatment group [REVAC group]) during the preconditioning phase of production. All cattle were given a modified-live respiratory virus vaccine. Eleven days later, REVAC group cattle received a second injection of the same vaccine. During the finishing phase of production, cattle from each treatment group were either vaccinated a third time with the modified-live respiratory virus vaccine or given no vaccine. Health observations were performed daily. Blood and performance variables were measured throughout the experiment. Results-During preconditioning, no significant differences were observed in performance or antibody production between groups. Morbidity rate from bovine respiratory disease was lower for SVAC group cattle; however, days to first treatment for bovine respiratory disease were not different between groups. No significant differences in body weights, daily gains, or dry-matter intake between groups were observed during the finishing phase. Revaccination treatment group cattle had improved feed efficiency regardless of vaccination protocol in the finishing phase. Conclusions and Clinical Relevance-Vaccination once with a modified-live respiratory virus vaccine was as efficacious as vaccination twice in the prevention of bovine respiratory disease of high-risk cattle, although feed efficiency was improved in REVAC group cattle during the finishing period.

Unlabelled: We developed several chimeric PlpE-leukotoxin (LKT) constructs containing the major epitope of Mannheimia haemolytica outer membrane lipoprotein PlpE (epitope R2) and the neutralizing epitope of M. haemolytica LKT (NLKT) [Ayalew et al. Mannheimia haemolytica chimeric protein vaccine composed of the major surface-exposed epitope of outer membrane lipoprotein PlpE and the neutralizing epitope of leukotoxin. Vaccine 2008;26(38):4955-61]. Vaccination of mice with these PlpE-LKT chimeric proteins stimulated anti-PlpE antibodies that caused complement-mediated bacteriolysis of M. haemolytica as well as neutralizing anti-LKT antibodies. Chimeric protein SAC89, which contains two copies of R2 and two copies of NLKT, generally stimulated the best overall responses in mice. The objectives of the current study were: (1) to determine through a dose titration study if vaccination of cattle with SAC89 stimulated antibodies to both PlpE and LKT and (2) evaluate SAC89-induced immunity against experimental M. haemolytica challenge of cattle. In the dose titration study, vaccine doses ranged from 100 to 400 microg. SAC89 significant anti-M. haemolytica surface and LKT antibodies were detected following vaccination with each dose. The vaccination/challenge study was conducted with 30 weaned beef cattle distributed among four groups: Control (no vaccine), 100 microg SAC89, M. haemolytica Bacterin, and SAC89+M. haemolytica bacterin. On day 42 after two vaccinations, cattle were challenged transthoracically with M. haemolytica. There was significant reduction (p<0.05) in lesion scores for the SAC89+bacterin-vaccinated group (74.6% reduction compared to control lesion scores) when compared to the other groups (34.7% and 35.6% reduction compared to control lesion scores). Evaluation of antibody responses demonstrated that the control group failed to develop antibody responses to M. haemolytica surface antigens or to LKT. Bacterin-vaccinated cattle developed anti-M. haemolytica antibodies after the second vaccination. SAC89- and SAC89+bacterin-vaccinated groups developed significant antibody responses 14 days after the first vaccination and further significant increases in antibodies after the second vaccination., Conclusions: Vaccination with the chimeric protein SAC89 in conjunction with a M. haemolytica bacterin stimulated significant protection against a severe transthoracic challenge with the bacterium.

Objective: To identify any adverse effects on health or performance in young dairy calves fed clinoptilolite mixed with milk replacer., Animals: 26 male Holstein calves (1 to 7 days old)., Procedures: Twice daily for 28 days, calves were fed milk replacer with no clinoptilolite (control group; n=8), 0.5% clinoptilolite (low-dosage group; 9), or 2% clinoptilolite (high-dosage group; 9); each calf consumed approximately 12% of its body weight (based on the replacer solids in the milk replacer mixture)/d. For each calf, subjective health assessments, weight and rectal temperature measurements, and CBC and serum biochemical analyses were performed at intervals. All calves underwent necropsy., Results: 2 calves were euthanized during the experiment because of bronchopneumonia or enteritis. Body weight and average daily gain did not differ among treatment groups. The percentage of monocytes and serum total protein concentration in the low-dosage group were higher than values in the control and high-dosage groups. Compared with values for either clinoptilolite-treated group, BUN concentration was greater in the control group. Serum globulin concentration differed significantly among groups (2.77, 2.50, and 2.36 g/dL in the low-dosage, control, and high-dosage groups, respectively). At necropsy, gross lesions associated with clinoptilolite treatment were not detected in any of the calves., Conclusions and Clinical Relevance: Even under stressful conditions, clinoptilolite fed at low or high dosages did not affect the performance of dairy calves and had no negative effect on WBC count and blood metabolite concentrations and enzyme activities. Clinoptilolite ingestion was not associated with treatment-specific gross changes.

The study objective was to determine health and performance of ranch calves from different preconditioning strategies during a 42-d receiving period when commingled with calves of unknown health histories from multiple sources. Steer calves from a single source ranch (RANCH) were weaned and immediately shipped to a feedlot (WEAN, initial BW = 247 +/- 29 kg); weaned on the ranch for 45 d before shipping, but did not receive any vaccinations (WEAN45, initial BW = 231 +/- 26 kg); or weaned, vaccinated with modified live viral vaccine, and held on the ranch for 45 d before shipping (WEANVAC45, initial BW = 274 +/- 21 kg). Multiple-source steers were purchased through auction markets (MARKET, initial BW = 238 +/- 13 kg), and upon receiving, a portion of ranch-origin steers from each weaning group was commingled with a portion of MARKET cattle (COMM). The experimental design was completely randomized with a 2 x 3 +1 factorial arrangement of treatments. Factors were RANCH vs. COMM and weaning management (WEAN vs. WEAN45 vs. WEANVAC45) as the factors; MARKET cattle served as the control. Calves of WEAN, WEAN45, and MARKET were vaccinated on arrival at the feedlot. Ranch-origin calves tended (P = 0.06) to have greater ADG than COMM or MARKET calves, although ADG was not affected (P = 0.46) by weaning management. Across the 42-d receiving period, DMI was not affected (P = 0.85) by cattle origin. However, MARKET, WEAN45, and WEANVAC45 calves consumed more (P < 0.001) DM than WEAN calves. Gain efficiency was not affected (P > or = 0.11) by treatment. Ranch-origin calves were less (P < 0.001) likely to be treated for bovine respiratory disease than MARKET calves; COMM calves were intermediate. Calves that were retained on the ranch after weaning (WEAN45 and WEANVAC45) were also less likely to be treated (P = 0.001) than MARKET or WEAN calves. As expected, differences in morbidity related to differences in health costs. Calves of WEAN45 and WEANVAC45 had less (P < 0.001) health costs than MARKET and WEAN calves. On arrival, serum haptoglobin concentrations were greater (P < 0.001) in MARKET and WEAN compared with WEAN45 and WEANVAC45 calves. Calves from a single source that are retained on the ranch for 45 d after weaning exhibit less morbidity and less health costs during the receiving period at the feedyard than when cattle are commingled or trucked to the feedyard immediately after weaning.

Objective: To compare antibody responses, feedlot morbidity and mortality rates, feedlot performance, and carcass value for calves vaccinated with 1 of 2 vaccination strategies and for unvaccinated control calves., Design: Randomized controlled clinical trial., Animals: 451 beef steers and heifers., Procedures: Calves were vaccinated with a modified-live infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea virus types 1 (BVDV1) and 2 (BVDV2), parainfluenza type 3 virus, and bovine respiratory syncytial virus vaccine and Mannheimia haemolytica and Pasteurella multocida bacterin-toxoid at approximately 67 and 190 days of age (group 1; n = 151) or at approximately 167 and 190 days of age (group 2; 150) or were not vaccinated (control; 150). Serum antibody titers were measured at approximately 2, 67, 167, 190, and 232 days of age. Morbidity and mortality rates, feedlot performance, and carcass value were recorded for 361 calves shipped to feedlots., Results: Percentages of calves seroconverting to IBRV, BVDV1, and BVDV2 were significantly higher for groups 1 and 2 than for the control group. Mean treatment costs were significantly lower for vaccinated than for control calves, and mean mortality rate was significantly higher for control calves than for group 1 calves. Feedlot performance and carcass value did not vary significantly among groups., Conclusions and Clinical Relevance: Results suggested that vaccination of beef calves with a 5-antigen modified-live virus vaccine at 67 and 190 days of age was as effective in terms of immunologic responses as was vaccination at 167 and 190 days of age.

The use of diagnostic ultrasound equipment is becoming widespread within various sectors of veterinary practice. Ultrasonographic examination has several advantages over other imaging modalities and it can be applied in hospital and ambulatory settings. It has the potential for widespread use in the diagnosis of disorders of several body systems in food animal species. This article describes its application to gastrointestinal, hepatobiliary, cardiothoracic, urogenital, and umbilical disorders. Normal and abnormal findings are portrayed and discussed. Accurate and timely use of this diagnostic modality requires a modest amount of training and practice, but it allows for relatively rapid, inexpensive, and noninvasive acquisition of clinically relevant data.

The transmission of bovine viral diarrhea virus (BVDV) from persistently infected (PI) heifers to adult seronegative goats was examined in this study. Ten seronegative adult goats were exposed to 4 PI heifers. None of the goats developed any clinical signs but all goats seroconverted by 42 days after exposure to the PI cattle. Results indicate that goats are susceptible to BVDV infection when housed with PI cattle.

Necropsy of 4 neonatal calves with a peracute syndrome of abdominal distention, diarrhea, dehydration, shock, and death revealed abomasal tympany, marked edema, hemorrhage, and emphysema of ruminal and abomasal walls and histopathologic lesions characteristic of forestomach acidosis. The presence of acid damage and the production of substantial quantities of gas strongly suggested that the pathogenesis of the syndrome involved exuberant fermentation of intragastric substrate. This supposition led to attempts to experimentally induce the syndrome by dosing neonatal calves with an alimentary tract flora, followed by milk replacer supplemented with excessive fermentable carbohydrate (D-glucose and cornstarch). Two of the 5 calves thus treated developed a syndrome very similar to that observed in naturally affected calves. Literature suggests involvement of several Clostridial species, Sarcina spp., and possibly other microbes or a combination thereof to be involved in very similar syndromes. Therefore it is suggested that this complex of lesions and clinical signs is not dependent on a single etiologic agent. Rather, it is proposed that the natural occurrence of disease requires a quantity of highly fermentable substrate (starch, glucose, lactose, etc.) and a bacterial flora that is capable of rapidly fermenting that particular substrate with a resultant production of gas and acid.

A total of 894 calves at high risk for bovine respiratory disease were processed at two sites and randomly assigned to receive one of three antimicrobial metaphylactic regimens to determine if a two-drug regimen offered any advantage over the more conventional one-course regimens. On arrival, calves received either a two-course regimen of ceftiofur crystalline free acid (CCFA) followed by tulathromycin 8 days later (Group 1) or a one-course regiment of CCFA (Group 2) or tilmicosin (Group 3). At Site A, morbidity was significantly lower (52%) in Group 1 than in Group 2 (76.3%) and Group 3 (78.4%). At Site B, morbidity was significantly lower in Group 1 (2.6%) than in Group 2 (9.4%) and Group 3 (7.2%).

Measurement of nitric oxide (NO) in the expired breath of crossbred calves received at a research facility was performed using tunable diode laser absorption spectroscopy. Exhaled NO (eNO) concentrations were measured using NO absorption lines at 1912.07 cm(-1) and employing background subtraction. The lower detection limit and measurement precision were determined to be approximately 330 parts in 10(12) per unit volume. A custom breath collection system was designed to collect lower airway breath of spontaneously breathing calves while in a restraint chute. Breath was collected and analyzed from calves upon arrival and periodically during a 42 day receiving period. There was a statistically significant relationship between eNO, severity of bovine respiratory disease (BRD) in terms of number of times treated, and average daily weight gain over the first 15 days postarrival. In addition, breathing patterns and exhaled CO2 showed a statistically significant relationship with BRD morbidity.

Bovine respiratory disease is the most common health issue affecting stocker cattle. There are several nonrespiratory diseases that affect stockers. The more common diseases include rumen tympany, infectious bovine keratoconjunctivitis, coccidiosis, photosensitization, and foot rot. Accurate diagnosis, early treatment, and incorporating appropriate preventive measures can assist cattle production.

Calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) represent an important source of infection for susceptible cattle. We evaluated vaccine efficacy using calves PI with noncytopathic BVDV2a for the challenge and compared tests to detect BVDV in acutely or transiently infected calves versus PI calves. Vaccination with 2 doses of modified live virus vaccine containing BVDV1a and BVDV2a protected the calves exposed to the PI calves: neither viremia nor nasal shedding occurred. An immunohistochemistry test on formalin-fixed ear notches and an antigen-capture enzyme-linked immunosorbent assay on fresh notches in phosphate-buffered saline did not detect BVDV antigen in any of the acutely or transiently infected calves, whereas both tests had positive results in all the PI calves.

Bovine viral diarrhea virus (BVDV) persistently infected (PI) calves represent significant sources of infection to susceptible cattle. The objectives of this study were to determine if PI calves transmitted infection to vaccinated and unvaccinated calves, to determine if BVDV vaccine strains could be differentiated from the PI field strains by subtyping molecular techniques, and if there were different rates of recovery from peripheral blood leukocytes (PBL) versus serums for acutely infected calves. Calves PI with BVDV1b were placed in pens with nonvaccinated and vaccinated calves for 35 d. Peripheral blood leukocytes, serums, and nasal swabs were collected for viral isolation and serology. In addition, transmission of Bovine herpes virus 1 (BHV-1), Parainfluenza-3 virus (PI-3V), and Bovine respiratory syncytial virus (BRSV) was monitored during the 35 d observation period. Bovine viral diarrhea virus subtype 1b was transmitted to both vaccinated and nonvaccinated calves, including BVDV1b seronegative and seropositive calves, after exposure to PI calves. There was evidence of transmission by viral isolation from PBL, nasal swabs, or both, and seroconversions to BVDV1b. For the unvaccinated calves, 83.2% seroconverted to BVDV1b. The high level of transmission by PI calves is illustrated by seroconversion rates of nonvaccinated calves in individual pens: 70% to 100% seroconversion to the BVDV1b. Bovine viral diarrhea virus was isolated from 45 out of 202 calves in this study. These included BVDV1b in ranch and order buyer (OB) calves, plus BVDV strains identified as vaccinal strains that were in modified live virus (MLV) vaccines given to half the OB calves 3 d prior to the study. The BVDV1b isolates in exposed calves were detected between collection days 7 and 21 after exposure to PI calves. Bovine viral diarrhea virus was recovered more frequently from PBL than serum in acutely infected calves. Bovine viral diarrhea virus was also isolated from the lungs of 2 of 7 calves that were dying with pulmonary lesions. Two of the calves dying with pneumonic lesions in the study had been BVDV1b viremic prior to death. Bovine viral diarrhea virus 1b was isolated from both calves that received the killed or MLV vaccines. There were cytopathic (CP) strains isolated from MLV vaccinated calves during the same time frame as the BVDV1b isolations. These viruses were typed by polymerase chain reaction (PCR) and genetic sequencing, and most CP were confirmed as vaccinal origin. A BVDV2 NCP strain was found in only 1 OB calf, on multiple collections, and the calf seroconverted to BVDV2. This virus was not identical to the BVDV2 CP 296 vaccine strain. The use of subtyping is required to differentiate vaccinal strains from the field strains. This study detected 2 different vaccine strains, the BVDV1b in PI calves and infected contact calves, and a heterologous BVDV2 subtype brought in as an acutely infected calf. The MLV vaccination, with BVDV1a and BVDV2 components, administered 3 d prior to exposure to PI calves did not protect 100% against BVDV1b viremias or nasal shedding. There were other agents associated with the bovine respiratory disease signs and lesions in this study including Mannheimia haemolytica, Mycoplasma spp., PI-3V, BRSV, and BHV-1.