Effects of commingling beef calves from different sources and weaning protocols during a forty-two-day receiving period on performance and bovine respiratory disease

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.     

The effect of bovine viral diarrhea virus infections on health and performance of feedlot cattle

The aim of this study was to investigate the effect of bovine viral diarrhea virus (BVDV) infections (unapparent acute infections and persistent infections) on the overall health and performance of feedlot cattle. Calves from 25 pens (7132 calves) were enrolled in the study. Overall and infectious disease mortality rates were significantly higher (P < 0.05) in pens categorized at arrival as positive for type I BVDV and lower in pens that were positive for type II BVDV than in negative pens. Mortality attributed to BVDV infection or enteritis was significantly more common (P < 0.05) in the pens containing persistently infected (PI) calves than in pens not containing PI calves (non-PI pens). There were no statistically detectable (P > or = 0.05) differences in morbidity, overall mortality, average daily gain, or the dry matter intake to gain ratio between PI and non-PI pens. Although type-I BVDV infections in feedlots appear to contribute to higher mortality rates, the presence of PI calves alone does not appear to have a strong impact on pen-level animal health and feedlot performance.     

Protective effects against abortion and fetal infection following exposure to bovine viral diarrhea virus and bovine herpesvirus 1 during pregnancy in beef heifers that received two doses of a multivalent modified-live virus vaccine prior to breeding

Objective-To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection. Design-Randomized controlled clinical trial. Animals-33 crossbred beef heifers, 3 steers, 6 bulls, and 25 calves. Procedures-20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days. Results-After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers. Conclusions and Clinical Relevance-Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.     

Rumen temperature change monitored with remote rumen temperature boluses after challenges with bovine viral diarrhea virus and Mannheimia haemolytica

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.     

Evolution of bovine viral diarrhea virus vaccines.

Control of bovine viral diarrhea virus (BVDV) infection is economically important to the cattle industry because the virus causes a variety of clinical diseases that adversely affect essentially all stages of the production cycle. Production losses primarily stem from reproductive failure and from immunosuppression during acute BVDV infection, which predisposes calves to respiratory or enteric diseases. Control is achieved by implementing herd health pro-grams focused on limiting exposure by avoiding persistently infected (PI) carrier cattle and by optimizing protective immunity through immunization. Vaccination cannot be relied upon solely to protect against fetal infection and losses due to BVD. This is because no single BVDV vaccine has been shown to give complete fetal protection. In addition to strategic use of vaccines, herd management practices should also be implemented to identify and eliminate PI carrier cattle and to avoid exposure to BVDV infection.     

Diagnosis of persistent bovine viral diarrhea virus infection by immunohistochemical staining of formalin-fixed skin biopsy specimens.

The objective of this study was to evaluate the efficacy of immunohistochemical (IHC) staining for diagnosis of persistent bovine viral diarrhea virus (BVDV) infection using formalin-fixed, paraffin-embedded skin biopsy specimens. Skin from 41 of 42 calves shown to be persistently infected (PI) with BVDV by repeated virus isolation more than 3 weeks apart were immunohistochemically positive for BVDV antigen. Positive IHC staining was most pronounced in the keratinocytes and in hair follicle epithelium, hair matrix cells of the hair bulb, and the dermal papilla. All of the skin sections from 10 calves experimentally infected postnatally with BVDV (10(5) median tissue culture infective doses [TCID50]) and biopsied on days 0, 5, 7, and 9 postinfection were negative for viral antigen. Ten calves from a second group experimentally infected with a higher dose of BVDV (10(8) TCID50) were biopsied when viremic between 10 and 14 days postinfection and 4 calves exhibited positive IHC staining for BVDV; however, staining in these skin biopsies was confined to small foci in the nonfollicular epidermis and follicular ostia. This staining was distinct from that observed in skin obtained from PI cattle. Skin biopsy represents an effective method for identifying animals PI with BVDV.     

Reproductive consequences of infection with bovine viral diarrhea virus.

Reproductive efficiency is imperative for the maintenance of profitability in both dairy and cow-calf enterprises. Bovine viral diarrhea virus is an important infectious disease agent of cattle that can potentially have a negative effect on all phases of reproduction. Reduced conception rates,early embryonic deaths, abortions, congenital defects, and weak calves have all been associated BVDV infection of susceptible females. In addition, the birth of calves PI with BVDV as a result of in utero fetal exposure is extremely important in the perpetuation of the virus in an infected herd or spread to other susceptible herds. Bulls acutely or PI with BVDV may bea source of viral spread through either natural service or semen used in artificial insemination. Management practices including elimination of PI cattle, biosecurity measures and strategic use of vaccination can be implemented to reduce the risk of BVDV related reproductive losses.Development of vaccines and vaccine strategies capable of providing better protection against fetal infection would be of benefit.     

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.     

Bovine viral diarrhea virus (BVDV) 1b: predominant BVDV subtype in calves with respiratory disease

The prevalence of bovine viral diarrhea virus (BVDV) infections was determined in 2 groups of stocker calves with acute respiratory disease. Both studies used calves assembled after purchase from auction markets by an order buyer and transported to feedyards, where they were held for approximately 30 d. In 1 study, the calves were mixed with fresh ranch calves from a single ranch. During the studies, at day 0 and at weekly intervals, blood was collected for viral antibody testing and virus isolation from peripheral blood leukocytes (PBLs), and nasal swabs were taken for virus isolation. Samples from sick calves were also collected. Serum was tested for antibodies to bovine herpesvirus-1 (BHV-1), BVDV1a, 1b, and 2, parainfluenza 3 virus (PI3V), and bovine respiratory syncytial virus (BRSV). The lungs from the calves that died during the studies were examined histopathologically, and viral and bacterial isolation was performed on lung homogenates. BVDV was isolated from calves in both studies; the predominant biotype was noncytopathic (NCP). Differential polymerase chain reaction (PCR) and nucleic acid sequencing showed the predominant subtype to be BVDV1b in both studies. In 1999, NCP BVDV1b was detected in numerous samples over time from 1 persistently infected calf; the calf did not seroconvert to BVDV1a or BVDV2. In both studies, BVDV was isolated from the serum, PBLs, and nasal swabs of the calves, and in the 1999 study, it was isolated from lung tissue at necropsy. BVDV was demonstrated serologically and by virus isolation to be a contributing factor in respiratory disease. It was isolated more frequently from sick calves than healthy calves, by both pen and total number of calves. BVDV1a and BVDV2 seroconversions were related to sickness in selected pens and total number of calves. In the 1999 study, BVDV-infected calves were treated longer than noninfected calves (5.643 vs 4.639 d; P = 0.0902). There was a limited number of BVDV1a isolates and, with BVDV1b used in the virus neutralization test for antibodies in seroconverting calves' serum, BVDV1b titers were higher than BVDV1a titers. This study indicates that BVDV1 strains are involved in acute respiratory disease of calves with pneumonic Mannheimia haemolytica and Pasteurella multocida disease. The BVDV2 antibodies may be due to cross-reactions, as typing of the BVDV strains revealed BVDV1b or 1a but not BVDV2. The BVDV1b subtype has considerable implications, as, with 1 exception, all vaccines licensed in the United States contain BVDV1a, a strain with different antigenic properties. BVDV1b potentially could infect BVDV1a-vaccinated calves.     

Associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus, antibodies against bovine viral diarrhea virus, or antibodies against infectious bovine rhinotracheitis virus in calves

OBJECTIVE: To measure associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus (BVDV), antibodies against BVDV, or antibodies against infectious bovine rhinotracheitis (IBR) virus in calves. ANIMALS: 1,782 calves from 61 beef herds. PROCEDURES: Calf serum samples were analyzed at weaning for antibodies against type 1 and type 2 BVDV and IBR virus. Skin biopsy specimens from 5,704 weaned calves were tested immunohistochemically to identify persistently infected (PI) calves. Herd production records and individual calf treatment and weaning weight records were collected. RESULTS: There was no association between the proportion of calves with antibodies against BVDV or IBR virus and herd prevalence of abortion, stillbirth, calf death, or nonpregnancy. Calf death risk was higher in herds in which a PI calf was detected, and PI calves were more likely to be treated and typically weighed substantially less than herdmates at weaning. Calves with high antibody titers suggesting exposure to BVDV typically weighed less than calves that had no evidence of exposure. CONCLUSIONS AND CLINICAL RELEVANCE: BVDV infection, as indicated by the presence of PI calves and serologic evidence of infection in weaned calves, appeared to have the most substantial effect on productivity because of higher calf death risk and treatment risk and lower calf weaning weight.     

Distribution of viral antigen and tissue lesions in persistent and acute infection with the homologous strain of noncytopathic bovine viral diarrhea virus.

Viral distribution and lesions were compared between calves born with persistent infection (PI) and calves acutely infected with the same bovine viral diarrhea virus (BVDV) isolate. Two PI calves from 1 dairy herd were necropsied. The PI viruses from these calves were isolated, characterized by sequencing, and found to be identical. This virus strain, designated BVDV2-RS886, was characterized as a noncytopathic (ncp) type 2 BVDV. To establish acute infections, BVDV2-RS886 was used to inoculate clinically healthy, seronegative calves which were 3 weeks to 3 months old. Nine calves received 10(6)-10(7) tissue culture infective dose of BVDV2-RS886 intranasally. Four additional age-matched animals served as noninfected controls. Infected calves were necropsied at 3, 6, 9, or 13 days postinoculation (dpi). Viral antigen was detected by immunohistochemistry in frozen sections, and lesions were evaluated in hematoxylin eosin-stained paraplast sections. In the PI calves, a wide distribution of viral antigen was found in all tissues and was not associated with lesions. In the acutely infected calves, viral antigen was widespread in lymphoid tissues at 6 dpi but had been mostly eliminated at 9 and 13 dpi. Depletion of lymphoid tissues was seen at 6, 9, and 13 dpi and repopulation at 9 and 13 dpi. In 1 of the calves at 13 dpi, severe arteritis was present in lymph nodes and myocardium. This comparison shows that an ncp BVDV strain that causes no lesions in PI animals is able to induce marked depletion of lymphoid tissues in calves with acute infection. Therefore, the failure to eliminate PI cattle from a herd causes problems not only in pregnant cattle but may also affect other age groups.     

Investigation of bovine viral diarrhea virus infections in a range beef cattle herd

Bovine viral diarrhea virus (BVDV) infections resulting in clinical disease developed in calves, despite vaccination of dams and high maternal BVDV antibody titers in calves. Eight persistently infected (PI) calves born to immunocompetent dams were identified in the herd. Neutralizing BVDV antibody titers of PI calves had decreased greatly by the time the calves were 1 to 2 months old. Antibody titers of PI calves decreased more rapidly than antibody titers of calves that were not PI. Reduced antibody titers in PI calves allowed detection of BVDV in serum specimens of all PI calves by the time they were 8 weeks old. Persistent infection in suspect calves was detectable serologically and was confirmed by virologic examination of serum specimens 4 months after weaning, when the calves were 9 months old. Growth rates were reduced in viremic calves.     

Prevalence of Neospora caninum and persistent infection with bovine viral diarrhea virus in dairy-breed steers in a feedlot

OBJECTIVE: To determine the prevalence and effect of Neospora caninum infection and persistent infection (PI) with bovine viral diarrhea virus (BVDV) on weight gain, morbidity, and mortality rate in dairy-breed steer calves located on a feedlot in California. DESIGN: Prospective cohort observational study. ANIMALS: 900 dairy-breed steer calves in 2 pens. PROCEDURES: The 3- to 4-month-old calves were evaluated for serum antibodies against N caninum and infection with BVDV at entry to the feedlot. Five months later, sera were again analyzed for anti-N caninum antibodies; calves that were determined to have BVDV infection initially were retested to evaluate PI status. Average daily gain, morbidity, and deaths were recorded for all calves. RESULTS: Among 900 calves, prevalence of N caninum infection was 16.7% (95% confidence interval, 14.3% to 19.3%); prevalence of BVDV-associated PI was 0.2% (95% confidence interval, 0.03% to 0.9%). Morbidity rate and time to first illness were not significantly different between calves that were seropositive or seronegative for N caninum. At the second sample collection, weight and average daily gain of calves that were seropositive for N caninum was less than that of seronegative steers in 1 pen, whereas these measures did not differ between groups in the other pen. Statistical power was insufficient to evaluate the effect of BVDV PI on any outcome measurement. CONCLUSIONS AND CLINICAL RELEVANCE: Although N caninum serostatus had no significant effect on morbidity rate, some seropositive calves had reduced growth, compared with seronegative calves, 5 months after entry to the feedlot.     

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.     

Platelet function and association of bovine viral diarrhea virus with platelets of persistently infected cattle

OBJECTIVE: To determine whether viral involvement with platelets obtained from cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) is associated with altered platelet function or decreased platelet counts. SAMPLE POPULATION: Platelets obtained from 8 cattle PI with BVDV and 6 age-, sex-, and breed-matched uninfected control cattle. PROCEDURE: Manual platelet counts were determined, and platelet function was assessed through optical aggregometry by use of the aggregation agonists ADP and platelet-activating factor. Identification of BVDV in serum and preparations of purified platelets was determined by use of virus isolation tests. RESULTS: No significant difference in platelet counts was detected between cattle PI with BVDV and control cattle. In response to the aggregation agonists, maximum aggregation percentage and slope of the aggregation curve were not significantly different between cattle PI with BVDV and control cattle. We isolated BVDV from serum of all PI cattle and from purified platelets of 6 of 8 PI cattle, but BVDV was not isolated from serum or platelets of control cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Isolation of BVDV from platelets in the peripheral circulation of cattle immunotolerant to BVDV does not result in altered platelet function or decreases in platelet counts.     

Field application of the combination of neutralizing test and virus isolation, so-called spot test, to detect herds including cattle persistently infected with bovine viral diarrhea virus

To detect herds including cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV), application of the combination of neutralizing antibody detection and virus isolation, so-called spot test, were performed on sera of 3 calves selected from each of 26 farms. Nine farms were judged as positive because 64 or more antibody titers were detected from 2 or more calves or BVDV was isolated from one or more calves. PI cattle were detected from 8 of the 9 farms. The positive judgment on one farm was obtained only when the indicator virus used on the neutralizing test was genotypically identical with the isolate from the farm. These results suggest that the spot test can be effective in detecting herds with PI cattle and that the accuracy may be influenced by the genotypes of the indicator viruses.