Immune response to bovine viral diarrhea virus (BVDV) vaccines detecting antibodies to BVDV subtypes 1a, 1b, 2a, and 2c.

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.

Transmission of bovine viral diarrhea virus to adult goats from persistently infected cattle.

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.

Diagnostic ultrasonography in ruminants.

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.

Evaluation of three antimicrobial regimens used as metaphylaxis in stocker calves at high risk of developing bovine respiratory disease.

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%).

Best management practices for newly weaned calves for improved health and well-being.

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.

Effect of bovine respiratory disease during the receiving period on steer finishing performance, efficiency, carcass characteristics, and lung scores.

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.

Feeding wet distillers grains plus solubles with and without a direct-fed microbial to determine performance, carcass characteristics, and fecal shedding of O157:H7 in feedlot heifers.

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.

Effect of copper, manganese, and zinc supplementation on the performance, clinical signs, and mineral status of calves following exposure to bovine viral diarrhea virus type 1b and subsequent infection.

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.

Effect of timing of challenge following short-term natural exposure to bovine viral diarrhea virus type 1b on animal performance and immune response in beef steers.

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.

Transmission of bovine viral diarrhea virus 1b to susceptible and vaccinated calves by exposure to persistently infected 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.

Nasal isolation of Mannheimia haemolytica and Pasteurella multocida as predictors of respiratory disease in shipped calves.

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.

Evaluation of multiple ancillary therapies used in combination with an antimicrobial in newly received high-risk calves treated for bovine respiratory disease.

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.

Cattle with increased severity of bovine respiratory disease complex exhibit decreased capacity to protect against histone cytotoxicity.

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

The effects of technology use in feedlot production systems on feedlot performance and carcass characteristics.

The objectives of this study were to examine the effects of feedlot production systems with and without the use of a ß-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 ß-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.

An atypical lymphoma of T-cell lineage in the thorax of an aged cow.

An aged beef cow was presented for signs of thoracic disease. A complete clinical and diagnostic workup suggested neoplasia. Postmortem examination revealed a lymphoma of T-cell lineage confined solely to the thoracic cavity, predominantly in lung tissue. The diagnosis was based on light and electron microscopy, immunohistochemistry, and negative bovine leukemia virus and bovine immunodeficiency virus results.

Evaluation of health status of calves and the impact on feedlot performance: assessment of a retained ownership program for postweaning calves.

The objective of this study was to evaluate animal health status at entry to a feedlot against feedlot performance and carcass value. There were 24 herds represented by 417 calves in a retained ownership program. The health status at entry was represented by the levels of serum antibody to infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea viruses 1 and 2 (BVDV1a, BVDV2), parainfluenza 3 virus (PI3V), bovine respiratory syncytial virus (BRSV), Mannheimia haemolytica, and Pasteurella multocida, as well as by the presence of virus in nasal swabs and blood leukocytes and the presence of bacteria in nasal swabs. The presence or absence of viruses or bacteria at entry did not predict subsequent illness. However, there were predictors of illness severity (number of treatments) and performance parameters of feedlot performance. Herds with a low morbidity rate had higher levels of BVDV1a antibodies than herds with a high morbidity rate. On both an individual-animal and a herd-average basis, calves with low levels of antibody to BVDV1a and BVDV2 had increased total treatment costs. Also, for individual animals and the herd as a whole, low levels of antibody to P. multocida, BVDV1a, and BVDV2 were related to decreased net value to owner (carcass value minus total feedlot cost). Calves treated twice or more had lower levels of antibody to BVDV1a than those treated once or not at all. Differences in herd morbidity rate and treatment costs were more related to appropriate timing of vaccine (last dose at or near delivery of calf) or lack of a 2nd dose of killed vaccine. This was best illustrated by the levels of antibody to BVDV1a. The results of this study were used to formulate recommendations for the subsequent year.

Severe masseter myonecrosis in a horse.

A 6-year-old Quarter Horse was examined because of acute, severely swollen masseter muscles (palpation of which elicited pain response), exophthalmos, severe chemosis, and protrusion of the third eyelids. Blood selenium and vitamin E concentrations, and results of feed analysis and muscle biopsy supported a diagnosis of nutritional myopathy. The horse was treated and was clinically normal 2 weeks after discharge from the hospital.

Motor neuron degeneration in a horse.

A 9-year-old Quarter Horse mare was examined because of progressive weight loss, weakness, muscle atrophy and tremors, and behavioral change. Selenium and glutathione peroxidase assays, blood lead analysis, erythrocyte transketolase analysis, pseudorabies and Borrelia burgdorferi serology, electromyography, and CSF analysis were performed. Motor neuron degeneration was diagnosed by microscopic examination of neural tissues. The cause of the disease was not substantiated, but several possibilities were excluded via diagnostic testing. Diagnosis of motor neuron degeneration in horses may be made from an accurate history, thorough neurologic examination, and ancillary testing. In particular, antemortem diagnosis may be based on finding scattered angular atrophy of predominantly type-1 or of type-1 and -2 skeletal muscle fibers in frozen sections of muscle biopsy specimens.

Assessment of the cardiovascular and lymphatic systems.

Assessment of the cardiovascular and lymphatic systems first requires a complete signalment, history, and general physical examination. Further assessment of the cardiovascular system begins with evaluation of the cardiac borders through palpation and thoracic percussion. Complete cardiac auscultation requires careful evaluation of several parameters. The location, intensity, and character of normal heart sounds are first determined. This is followed by assessment of heart rate and rhythm. Finally, special attention should be placed on identifying abnormal heart sounds and describing them based on their location, intensity, duration, sound quality, and radiation. Assessment of the arterial, venous, and capillary systems provides additional information on the status of the cardiovascular system. Assessment of the lymphatic system primarily involves evaluation of external and palpable internal lymph nodes. Commonly palpable external lymph nodes include the intermandibular, parotid, retropharyngeal, superficial cervical, subiliac, mammary, and scrotal lymph nodes. Palpable internal abdominal lymph nodes include the iliofemoral lymph nodes and the iliosacral lymph center. Other lymph nodes that may be palpable include the renal, ruminal, and mesenteric lymph nodes. Lymph nodes should be evaluated for size, consistency, and tenderness.