Comparison of beef traceability in serial and parallel fabrication systems using RFID and two-dimensional barcodes.

Traceability of beef attributes from small- and mid-sized farms through supply chains is a market barrier. The objective of this trial was to determine the influence of fabrication method on beef traceability system requirements. Individual identities of 54 animals were maintained through harvest, processing, packaging, and distribution. At harvest, each animal's unique radio frequency identification (RFID) animal identification number was transferred to a harvest label on each carcass quarter. Following transportation to a processor, nine carcasses were processed on alternating days by one of the two methods. Carcasses were fabricated, using a serial fabrication method (SFM), into wholesale cuts one at a time or fabricated using a parallel fabrication method (PFM), by processing multiple hindquarters or forequarters simultaneously into wholesale cuts. In-process labels were generated by scanning the two-dimensional (2D) barcode on the harvest label with a handheld mobile computer and printed from a wireless mobile printer. Tracking of SFM and PFM carcass quarters was accomplished by creating in-process labels for lugs and individual wholesale cuts, respectively. The process was recorded and the data was captured from video analysis. The mean number of in-process labels generated per carcass for SFM was 3.7 and for PFM was 30.9 (P < 0.01). The amount of time required for generating in-process labels for SFM (2 min 16 s) was less than PFM (8 min 45 s) (P = 0.01). The amount of time required to label each carcass was less (P < 0.01) for SFM (18 s) than for PFM (3 min 10 s) with in-process labels. Total cost of traceability, including fixed and consumable cost per carcass, was nearly twice as much for PFM ($17.98) than SFM ($9.02). Traceability, within both processing methods, was found to have 100% fidelity, as verified using DNA marker genotyping. Overall, the number of labels generated for traceability was less for SFM than that for PFM. The overall time spent on generating, applying, and removing labels was less for SFM than that for PFM. The total cost of traceability was approximately half for SFM compared with that for PFM; however both methods were able to track product accurately. Tracking of beef from individual animals, using RFID ear tags and 2D barcodes, appears to be feasible for the fabrication methods used in this study.

Short communication: use of the BetaStar Plus assay for detection of ceftiofur antimicrobial residues in milk from individual cows following intramammary treatment for mastitis.

Development and use of on-farm assays to detect antimicrobial residues in milk is important to reduce the risk of violative residues in marketed milk. The objective of this study was to evaluate the effectiveness of a lateral-flow immunodiagnostic assay (BetaStar Plus, Neogen Corp., Lansing, MI) in detecting ceftiofur residues in milk from individual cows treated for mastitis. This assay is currently approved by the US Federal Drug Administration (FDA) for detecting ß-lactam residues in commingled milk. Forty-five dairy cows with clinical mastitis from 4 dairy farms were enrolled and treated intramammary with 125 mg of ceftiofur hydrochloride (Spectramast LC, Zoetis, Madison, NJ) according to the manufacturer's label recommendation. Composite milk samples were collected (A) before first intramammary antimicrobial treatment, (B) before the last intramammary antimicrobial treatment, (C) the last milking of the product-labeled milk withhold, (D) the first milking after the product-labeled milk withhold had been met, and (E) 72 h after the product-labeled milk withhold had been met. Samples were tested using the BetaStar Plus assay within 48 h of collection. Parallel samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and for somatic cell count and milk components. The BetaStar Plus assay identified 6.7, 60.0, 46.7, 22.2, and 6.7% positive samples at each of the respective time points. The assay had sensitivity and specificity of 100 and 84.7%, respectively, compared with liquid chromatography-tandem mass spectrometry analysis using FDA published residue tolerance levels for ceftiofur (or ceftiofur metabolites) as a threshold. The BetaStar Plus assay could be useful for detecting ceftiofur residues in milk from individual cows following intramammary treatment for mastitis before the milk is shipped for processing.

Application of an ELISA Milk Pregnancy Test in Beef Cows.

Pregnancy-associated glycoproteins (PAG) are secreted by the binucleate giant cells of the ruminant placenta and enter maternal circulation at the time of placental attachment. The IDEXX Milk Pregnancy Test (IDEXX, Westbrook, ME) detects a subset of PAG in milk. Although designed as a management tool for dairy cows, there is potential for using the milk PAG test in beef cows. Our objective was to compare the performance of the milk PAG ELISA with a gold standard method for pregnancy diagnosis and determine the agreement between milk and serum PAG analysis in lactating beef cows. Angus and Angus-crossed cows (n = 332) from two Michigan beef herds were enrolled in this study. Cows were subjected either to timed artificial insemination followed by exposure to a bull or exclusively exposed to a bull. The bulls and cows were separated 30 days prior to examination. Serum and milk samples were collected and submitted within 24 h of collection to a commercial laboratory for PAG analysis using the IDEXX Milk Pregnancy Assay (milk) and the IDEXX Bovine Pregnancy Assay (serum). Concurrently with milk and serum collection, each cow was examined transrectally by palpation or ultrasonography. When compared to transrectal examination, the performance (and 95% confidence intervals) of the milk PAG ELISA was sensitivity of 99.7% (99.0-100.0%) and specificity of 80.8% (65.6-95.9%). The lower specificity is likely due to the low prevalence (9.9%) of open cows (n = 30) in the herds examined. Of the 332 cows examined, 1.8% (n = 6) were classified as rechecks using the milk PAG ELISA. Results of the milk and serum PAG ELISA were in high agreement (kappa coefficient = 0.91). The milk PAG ELISA was accurate in predicting pregnancy status using milk collected from beef cattle between days 37 and 125 post-insemination and may be useful for aiding management decisions in beef herds.

Rapid Detection of Bovine Respiratory Syncytial Virus in Poland Using a Human Patient-Side Diagnostic Assay.

Bovine respiratory syncytial virus (BRSV) plays a significant role in the etiopathogenesis of the respiratory syndrome in young cattle during their first year of life. Development of rapid and accurate BRSV diagnostic tools would aid in the appropriate control of this important pathogen. The objective of this study was to characterize infections induced by BRSV by means of rapid patient-side immunomigration assays used for diagnosis of human respiratory syncytial virus (hRSV) in humans. Nasal and tracheal swabs were obtained from healthy calves of various beef and dairy breeds - Holstein-Friesian, Simmental, Charolais, Belgian Blue and Limousin, between the ages of 5 and 12 months, from 26 farms. BRSV was identified using two rapid immunomigration assays, TruRSV® and Clearview® RSV, and compared with RT-PCR as a reference technique. BRSV was found in 73.1% of all the herds tested. High agreement with RT-PCR was obtained for TruRSV® (κ = 0.824), while in the case of the Clearview® RSV test, agreement with PCR was moderate (κ = 0.420). The results demonstrate that rapid patient-side immunomigration assays designed to detect hRSV can be used to accurately detect BRSV in field samples collected from cattle.

Effects of tail docking on behavior of confined feedlot cattle.

Tail tip injuries occur in some feedlot cattle housed in slatted-floor facilities typically found in the midwestern United States. The practice of tail docking cattle on entry into these feedlot facilities was initiated to prevent tail injuries. Tail docking is a welfare concern from the standpoint that an important method of fly avoidance is removed and the tail docking procedure is painful and often excludes local anesthesia or extended analgesia. The primary objective of this study was to describe the behavioral responses of feedlot cattle following tail docking. Thirty-six heifers were randomly assigned to 1 of 2 treatment groups: docked (DK) or control (CN). All calves received an epidural following surgical preparation of the sacrococcygeal area and postoperative intravenous flunixin meglumine. A portion of the tail of DK calves was removed using pruning shears. An elastrator band was placed near the tail tip for hemostasis and tail tips were sprayed with fly spray. IceQube accelerometers collected step counts, motion index, lying time, lying bouts, and lying bout duration during d -4 through 13. Direct observations of cattle behavior were performed on d 0, 1, and 2. Step counts of DK calves were increased (P < 0.05) on d 0, 2, 3, 4, 6, 9, 10, and 13, and motion index of DK calves was also increased (P < 0.05) on d 0, 3, 4, 9, 10, 11, and 13. Docked cattle performed rear foot stomp behavior more (P < 0.001) than CN on d 0, 1, and 2. Forty-eight hours after tail docking, DK calves had increased lying bouts per hour (1.7 vs. 0.9 on d 0; P < 0.001; 1.1 vs. 0.8 on d 1; P < 0.01) but reduced lying bout durations (12.6 vs. 47.1 min on d 0; P < 0.001; 22.6 vs. 44.7 min on d 1; P < 0.001). On d 0, DK calves twitched tails more (P < 0.05) and ruminated less (P < 0.001). Despite provision of perioperative and postoperative analgesia, we identified altered behavior in DK cattle that may reflect a compromised welfare state for tail-docked feedlot cattle. We recommend that alternative strategies to reduce tail tip injury be explored.

Effects of tail docking on health and performance of beef cattle in confined, slatted-floor feedlots.

Tail docking of feedlot cattle is a management practice used in some confined, slatted-floor feedlots of the midwestern United States. Justification for tail docking in these management systems is to reduce tail injuries and their sequelae and improve performance, but limited evidence exists to support these claims. The primary objective of this study was to determine the effect of tail docking on performance, carcass traits, and health parameters after tail docking in feedlot cattle raised in slatted-floor feedlots. Three separate trials were performed. Trial 1 consisted of 140 Angus-cross (370-kg) yearling steers that spent 144 to 160 days on feed (DOF). Trial 2 consisted of 137 Angus-cross (255-kg) weaned steers that spent 232 DOF. Trial 3 consisted of 102 Holstein steers (370 kg) that spent 185 to 232 DOF. Cattle were randomly assigned to 1 of 2 treatment groups: docked (DK) or control (CN). All steers received an epidural following surgical preparation of the sacrococcygeal area and postoperative intravenous flunixin meglumine. Approximately two-thirds of the tail of DK calves was removed and an elastrator band was placed near the tail tip for hemostasis. Performance parameters collected included daily gain, final weight, feed intake, and feed efficiency. Carcass data included HCW, subcutaneous fat thickness, LM area, KPH percent, marbling, USDA yield grade, and USDA quality grade. Morbidity, mortality, incidence of lameness, and incidence of tail lesions were recorded. Across all 3 trials, there was no significant effect (P < 0.05) of treatment on performance parameters, carcass traits, or health parameters. In all 3 trials, tail tip injuries occurred in 60 to 76% of undocked (CN) calves, developed while living in the slatted-floor environment, compared to 100% of DK calves, whose injuries were a result of the tail docking procedure. We were unable to identify a performance or significant health advantage to tail docking. However, tail tip injuries still occur in cattle raised in slatted-floor facilities. Because of the animal welfare issues associated with tail docking and tail injuries, we recommend pursuing alternative solutions to reducing the incidence of tail tip injury in feedlot cattle housed in confined slatted-floor facilities.

Evaluation of the interferon-γ assay on blood collected at exsanguination of cattle under field conditions for surveillance of bovine tuberculosis.

Development of point of concentration (POC) surveillance strategies for bovine tuberculosis (bTB) would facilitate global efforts to eradicate bTB. The interferon-gamma (IFNγ) assay can detect IFNγ responses to Mycobacterium bovis in blood collected at commencement of exsanguination (COE) of experimentally challenged cattle but has not been evaluated under field conditions. The current study was aimed at determining (i) whether blood collected at COE of cattle at slaughter, under field conditions, is practical to obtain and useful for identifying cattle as IFNγ positive for bTB, (ii) whether the results of the IFNγ assay obtained at COE reliably compare with results obtained from live animals in the field, and (iii) whether the identified animal(s) originated from bTB-infected or bTB-exposed herds. Cattle from three risk groups were used: the highest risk group consisted of 49 cattle from 3 bTB-infected herds; the medium risk group consisted of 24 cattle from a potentially exposed herd; and the lowest risk group consisted of 60 cattle from herds with no known history of bTB exposure. The IFNγ assay was performed on blood collected both before stunning and at COE of cattle at slaughter. An enhanced slaughter inspection for gross lesions consistent with bTB was performed on all cattle. In addition, lymph nodes were cultured for M. bovis for cattle that tested positive for bTB via the IFNγ assay and for most cattle that tested negative for bTB. Cattle, both with and without lesions consistent with bTB, were identified as positive for bTB by the IFNγ assay using blood collected at COE, but none of the positive cattle originated from the lowest risk group. The current study demonstrates that blood collected at COE of cattle is both a practical and moderately reliable sample for accessing bTB infection using the IFNγ assay.

Detection of Mycobacterium avium subspecies paratuberculosis in naturally exposed dairy heifers and associated risk factors.

An observational prospective study was conducted to identify risk factors associated with fecal shedding of Mycobacterium avium ssp. paratuberculosis (MAP) in naturally exposed dairy heifers. The study population consisted of heifers from 8 dairy herds in Michigan participating in a MAP control demonstration project. Ten heifers from 4 age groups (0 to 3, 4 to 6, 7 to 14, and 15 to 24 mo) were selected from each herd every 4 mo for 28 mo and tested for the presence of MAP by fecal culture (FC). Heifers from dams testing positive for MAP by serum ELISA or FC were preferentially selected, with the remainder of the age cohort filled with randomly selected heifers. Logistic regression using generalized estimating equations to account for clustering of data within herds and repeated measures across heifers was used to evaluate the relationship between MAP FC status of heifers and herd risk factors. In total, 1,842 fecal samples were collected from 1,202 heifers. Thirty-six (2%) fecal samples, representing 27 individual heifers, cultured positive for MAP. Heifers shedding MAP were more likely to occur in herds with adult-cow MAP ELISA prevalence >10% (odds ratio = 4.7; 95% confidence interval: 2.0-11.1) and herds milking >300 cows (odds ratio = 5.7; 95% confidence interval: 2.4-13.4). Mycobacterium avium ssp. paratuberculosis can be cultured from the feces of naturally infected dairy heifers. The future performance of these MAP FC-positive heifers is unknown and needs to be explored.

Case-control study: Productivity and longevity of dairy cows that tested positive for infection with Mycobacterium avium ssp. paratuberculosis as heifers compared to age-matched controls.

A case-control study was performed to determine if dairy heifers testing positive for Mycobacterium avium ssp. paratuberculosis (MAP) before 2 yr of age by either fecal culture or serum ELISA had decreased productivity and longevity as cows compared with age-matched herdmates. Cases were individually matched with 4 controls. Survival analysis was conducted to determine differences in longevity between cases and controls. Conditional logistic regression was used to assess differences in mean 3.5% fat-corrected 305-d mature-equivalent milk, milk fat, and milk protein production, linear somatic cell count, and MAP test and clinical status as mature cows. No significant difference was found between cases and controls for any parameter assessed. Herd production performance and longevity did not appear to be impaired; therefore, testing immature dairy heifers for MAP is not economically justifiable, using currently available culture methods and commercial serum ELISA tests.

Association between risk-assessment scores and individual-cow Johne's disease-test status over time on seven Michigan, USA dairy herds.

To evaluate the effectiveness of management practices implemented to control the spread of Johne's disease (JD), we conducted a 5-year observational study (January 2003 to December 2007) on seven Michigan, USA dairy herds containing cows infected with Mycobacterium avium subsp. paratuberculosis (MAP; the causative agent of the disease). The JD incidence and prevalence was monitored in each herd annually by serum ELISA and/or fecal culture of all adult cows. A JDCP was designed specifically for each herd based on the results of an initial risk-assessment. The risk-assessment was repeated annually and the control program updated as needed. Herd risk-assessment scores were used to measure compliance with the control program and create JD-risk profiles for individual cows raised on the farms. The association between specific risk-assessment scores and the JD-test status of individual cows was evaluated using logistic regression. We accounted for clustering of cows within herds using generalized estimating equations (GEE). Multivariable models were built with purposeful selection of risk factors assessed on univariable analyses. The dataset analyzed consisted of 3707 cows raised on the respective farms, of which 616 were classified as infected with MAP based on testing positive on fecal culture or serum ELISA. Of the cows that were not exposed to the control program, 20% were classified as infected, while only 7% of cows that were exposed to the control program were infected. The final multivariable model consisted of two factors: exposure to adult cows other than dam at birth (OR=1.09, 95% CI: 1.06, 1.13), and feeding colostrum from one cow to multiple calves (OR=1.10, 95% CI: 1.09, 1.12). Based on this study, implementing practices that minimize the exposure of newborn calves to MAP being shed by infected adult cows should take priority.

Economic evaluation of Johne's disease control programs implemented on six Michigan dairy farms.

Johne's disease (JD) is an incurable, chronic infectious disease prevalent in dairy herds throughout the US and the world. The substantial economic losses caused by JD have been well documented. However, information on the costs of controlling the disease is limited, yet necessary, if producers are to make sound decisions regarding JD management. The purpose of this paper is to describe a method for evaluating the cost-effectiveness of management changes to control JD on infected dairy farms. A 5-year longitudinal study of six dairy herds infected with JD was performed. Each herd implemented a JD control program upon study enrollment. Prevalence of JD within each herd was monitored with annual testing of all adult cows using fecal culture and/or serum ELISA. Individual cow production and culling information was collected to estimate the annual economic losses caused by JD. An economic questionnaire was developed and administered to each herd annually to estimate costs directly attributable to the JD control program. Based on the costs of the control program, and using the losses to estimate the potential benefits of the control program, the net present value (NPV) of the control program was calculated for each herd during the study and projected into the future for a total of 20 years. The NPV was calculated for four different scenarios: (1) assuming a linear decline in losses beyond the observed period of the study with JD eradication by year 20 of the control program; (2) assuming losses and JD prevalence remain constant at the rate equal to that of the last observed year while continuing the control program; (3) assuming linear increase in losses at rate equal to that in scenario 1 with no control program; and (4) assuming losses remain constant at same level as the beginning of the study with no control plan implemented. The NPV varied greatly across the herds. For scenario 1, only three herds had a positive NPV; and only two herds had a positive NPV under scenario two. In the absence of a control program, the NPV's were always negative. The costs of the JD control programs implemented on these herds averaged $30/cow/year with a median of $24/cow/year. The annual losses due to JD averaged $79/cow/year with a median of $66/cow/year. Investing in a JD control program can be cost-effective.

Prevalence of Michigan dairy herds infected with Mycobacterium avium subspecies paratuberculosis as determined by environmental sampling.

A cross-sectional, stratified random survey of Michigan dairy herds was conducted to estimate the prevalence of herds infected with Mycobacterium avium paratuberculosis (MAP), the causative agent of Johne's disease, in Michigan using targeted environmental sampling. One pooled sample each from the primary manure storage area and a high-traffic common cow area from each herd was collected and cultured for MAP using the ESP culture system II. A herd was classified as positive if at least one sample was culture positive for MAP. State, agricultural district, and herd size stratum prevalence were calculated. Information on past MAP testing and cattle purchase history was collected, and logistic regression was performed to determine their importance to the MAP status of the herd. One hundred twenty-seven herds were contacted, and 94 agreed to participate in the study. The environment of 38 (40.4%) herds cultured positive for MAP. MAP was found in all herds (n = 15) with greater than 200 lactating cows. Herds that had tested for MAP or purchased cattle in the previous 5 years were 4.6 and 3.1 times, respectively, more likely to be infected than herds that had not. MAP continues to be prevalent on Michigan dairy farms, especially those with greater than 200 lactating cows. The environmental sampling protocol used in this study is an economically attractive alternative for monitoring herd level prevalence and the progress of Johne's disease control programs at the state or national level. Implementation of such a program would aid states in monitoring Johne's control program progress, and guide changes over time.

Study of cattle persistently infected with bovine viral diarrhea virus that lack detectable virus in serum.

OBJECTIVE: To determine whether cattle persistently infected with bovine viral diarrhea virus (BVDV) that lack virus detectable in serum by use of the immunoperoxidase microtiter assay (IPMA) can transmit the virus to susceptible herdmates and determine prevalence of these cattle. DESIGN: Clinical trial and serologic survey. SAMPLE POPULATION: 2 cattle and 1,952 blood samples. PROCEDURE: A persistently infected cow in which virus could not be detected in serum was housed with a BVDV-seronegative steer. Blood and nasal swab specimens were tested via virus isolation and serum virus neutralization. Parallel WBC preparations and sera from blood samples of 1,952 adult cows were screened for BVDV by use of IPMA. RESULTS: The steer seroconverted to BVDV within 4 weeks of contact with the cow. Virus was detected in sera and WBC of 5 adult cows that were verified as persistently infected by retest 3 weeks later. Cattle persistently infected with BVDV in which virus could not be detected in both serum and WBC by use of IPMA were not found. CONCLUSION AND CLINICAL RELEVANCE: Cattle persistently infected with BVDV in which virus cannot be detected in serum by use of IPMA may serve as virus reservoirs for infecting susceptible cattle. Persistent infection was detected at a prevalence of 0.26%. Screening adult cattle by use of IPMA on serum samples appears to be a reliable means of detecting persistent infection with BVDV. Prevalence of cattle persistently infected with BVDV that have negative results of IPMA on serum is extremely low.

Relationship between degree of viremia and disease manifestation in calves with experimentally induced bovine viral diarrhea virus infection.

OBJECTIVE: To compare degree of viremia and disease manifestations in calves with type-I and -II bovine viral diarrhea virus (BVDV) infection. ANIMALS: 16 calves. PROCEDURE: Colostrum-deprived calves obtained immediately after birth were assigned to 1 control and 3 treatment groups (4 calves/group). Calves in treatment groups were inoculated (day 0) by intranasal instillation of 10(7) median tissue culture infective dose BVDV 890 (type II), BVDV 7937 (type II), or BVDV TGAN (type I). Blood cell counts and virus isolation from serum and leukocytes were performed daily, whereas degree of viremia was determined immediately before and 4, 6, 8, and 12 days after inoculation. Calves were euthanatized on day 12, and pathologic, virologic, and immunohistochemical examinations were performed. RESULTS: Type-II BVDV 890 induced the highest degree of viremia, and type-I BVDV TGAN induced the lowest. Virus was isolated more frequently and for a longer duration in calves inoculated with BVDV 890. A parallel relationship between degree of viremia and rectal temperature and an inverse relationship between degree of viremia and blood cell counts was observed. Pathologic and immunohistochemical examinations revealed more pronounced lesions and more extensive distribution of viral antigen in calves inoculated with type-II BVDV. CONCLUSIONS AND CLINICAL RELEVANCE: Degree of viremia induced during BVDV infection is associated with severity of clinical disease. Isolates of BVDV that induce a high degree of viremia may be more capable of inducing clinical signs of disease. Strategies (eg, vaccination) that reduce viremia may control clinical signs of acute infection with BVDV.

Platelet aggregation responses and virus isolation from platelets in calves experimentally infected with type I or type II bovine viral diarrhea virus.

Altered platelet function has been reported in calves experimentally infected with type II bovine viral diarrhea virus (BVDV). The purpose of the present study was to further evaluate the ability of BVDV isolates to alter platelet function and to examine for the presence of a virus-platelet interaction during BVDV infection. Colostrum-deprived Holstein calves were obtained immediately after birth, housed in isolation, and assigned to 1 of 4 groups (1 control and 3 treatment groups). Control calves (n = 4) were sham inoculated, while calves in the infected groups (n = 4 for each group) were inoculated by intranasal instillation with 10(7) TCID50 of either BVDV 890 (type II), BVDV 7937 (type II), or BVDV TGAN (type I). Whole blood was collected prior to inoculation (day 0) and on days 4, 6, 8, 10, and 12 after inoculation for platelet function testing by optical aggregometry by using adenosine diphosphate and platelet activating factor. The maximum percentage aggregation and the slope of the aggregation curve decreased over time in BVDV-infected calves; however, statistically significant differences (Freidman repeated measures ANOVA on ranks, P < 0.05) were only observed in calves infected with the type II BVDV isolates. Bovine viral diarrhea virus was not isolated from control calves, but was isolated from all calves infected with both type II BVDV isolates from days 4 through 12 after inoculation. In calves infected with type I BVDV, virus was isolated from 1 of 4 calves on days 4 and 12 after inoculation and from all calves on days 6 and 8 after inoculation. Altered platelet function was observed in calves infected with both type II BVDV isolates, but was not observed in calves infected with type I BVDV. Altered platelet function may be important as a difference in virulence between type I and type II BVDV infection.

Protection of pregnant cattle and their fetuses against infection with bovine viral diarrhea virus type 1 by use of a modified-live virus vaccine.

OBJECTIVE: To determine efficacy of a vaccine containing modified-live bovine viral diarrhea virus (BVDV) type 1 for protecting pregnant cows and their fetuses against virulent heterologous BVDV type 1. DESIGN: Randomized controlled cohort study. ANIMALS: 18 yearling beef heifers seronegative for BVDV and negative when tested for BVDV by virus isolation. PROCEDURE: Cattle were randomly assigned to control (unvaccinated; n = 6) or vaccinated (12) groups. Vaccinated heifers were given a combination vaccine containing modified-live BVDV type 1 comprising a cytopathic (NADL) strain. All 18 heifers were then bred and challenge-exposed between 70 and 75 days of gestation with BVDV type 1, administered intranasally. Cattle were monitored, and infection status of offspring was determined after parturition. Antibody concentrations of vaccinated and control heifers were also monitored. RESULTS: All 6 calves from control heifers had positive results on multiple virus isolation tests and were considered persistently infected. In comparison, only 2 calves from vaccinated cows had positive results on virus isolation tests and were considered persistently infected. One vaccinated heifer aborted, but the fetus was not persistently infected, and the abortion was not attributed to BVDV infection. CLINICAL IMPLICATIONS: Analysis of these data indicated that a single dose of a modified-live NADL-derived BVDV type 1 vaccine will confer protection to dams and their fetuses against challenge-exposure to heterologous BVDV type 1 organisms.

Detection of bovine viral diarrhea virus in the ovaries of cattle acutely infected with bovine viral diarrhea virus.

Bovine viral diarrhea virus (BVDV) is recognized worldwide as a major cause of economic loss in cattle. Infection with BVDV can result in several clinical outcomes. However, the reproductive consequences may be the most important. Infertility, early embryonic death, abortion, and congenital anomalies have all been reported following acute infection with BVDV. The cause of infertility following acute BVDV infection is not known. BVDV has been isolated from the bovine ovary and has been associated with chronic oophoritis. The purpose of this study was to identify the ovarian cell types infected with BVDV following acute infection. Twelve heifers were acutely infected with noncytopathic BVDV, and ovariectomies were performed between 4 and 60 days postinfection. BVDV was isolated on days 6 and 8 postinfection. Viral antigen was detected in macrophage-like cells and stromal cells in the ovarian cortex and oophoritis was evident from 6 to 60 days postinfection. These findings indicate that acute infection with BVDV may result in changes in ovarian function that could lead to reduced fertility.

Detection of cytopathic bovine viral diarrhea virus in the ovaries of cattle following immunization with a modified live bovine viral diarrhea virus vaccine.

Economic loss from infection with bovine viral diarrhea virus (BVDV) is of worldwide concern. The unique pathogenesis and antigenic variability of BVDV have made this virus challenging to control. Vaccination programs are a major component of control and prevention strategies. Both killed and modified live vaccines are commercially available. Choice between killed and modified live vaccines is controversial. Of major concern is the safety of modified live vaccines. Little information is available on their tissue tropism and potential for causing pathology, especially with respect to the reproductive system. The objective of this study was to determine if BVDV could be detected in the ovary of cattle following immunization with a modified live BVDV vaccine. In 2 separate trials, 6 heifers and 4 mature cows were immunized with a modified live BVDV vaccine and ovaries were removed between 7 and 30 days postvaccination. Cytopathic BVDV was isolated from ovaries removed on days 8, 10, and 12. BVDV antigen was detected using immunohistochemistry on days 10-30. These findings are significant because replication of virus in the ovary could cause ovarian dysfunction, resulting in reduced fertility.

Changes in levels of viremia in cattle persistently infected with bovine viral diarrhea virus.

Virus isolation and serum neutralizing antibody titers were determined over a period of time from samples collected from animals persistently infected with bovine viral diarrhea virus (BVDV). To evaluate over time the ability to detect BVDV by virus isolation from serum or white blood cell preparations, 4 persistently infected calves were monitored from birth until 70 days of age. In 3 of 4 persistently infected calves, virus isolation from serum and white blood cells was negative until approximately 42 days of age, when colostral antibody had declined. The level of viremia in 7 adult (> 12 months) persistently infected animals decreased by 1 10-fold dilution over at least a 2-year period. The level of viremia became undetectable by virus isolation from serum in 1 of the 7 animals examined. This decline was associated with the development of virus neutralizing antibody. Although the level of viremia is fairly stable within persistently infected animals, the presence of specific neutralizing antibody may affect the ability to isolate BVDV. These findings are important when considering diagnostic testing to identify persistently infected animals by virus isolation.