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.     

Health performance of feeder calves sold at conventional auctions versus special auctions of vaccinated or conditioned calves in Ontario

OBJECTIVE: To compare health performance during the first 28 days in the feedlot for vaccinated or conditioned feeder calves sold through special auctions in Ontario with health performance for calves sold through conventional auctions in the province. DESIGN: Cohort study. ANIMALS: 12,313 calves sold through conventional and special auctions at the Keady Livestock Market during the fall of 1999 and 2000. PROCEDURE: Buyers of calf groups were approached at the auction market or contacted by telephone and asked to record the number of calves requiring treatment for bovine respiratory tract disease (BRD) during the first 28 days after purchase. RESULTS: 211 calf groups (> or = 20 calves/group) were followed up for 28 days after purchase. Multivariate logistic analysis indicated that vaccinated calves purchased through special auctions were 0.68 (95% confidence interval, 0.50 to 0.93) times as likely to receive treatment for BRD as were calves purchased at conventional auctions and that conditioned calves were 0.22 (95% confidence interval, 0.12 to 0.38) times as likely to receive treatment. Groups that received antimicrobials by injection on arrival at the feedlot were 0.64 (95% confidence interval, 0.43 to 0.96) times as likely to be treated as were groups that did not. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that vaccinated and conditioned calves were less likely to receive treatment for BRD during the first 28 days in the feedlot; however, there was no difference in mortality rate.     

Five field trials on the efficacy of a bovine respiratory syncytial virus vaccine

Five field trials evaluated whether immunization of beef cattle prior to weaning, at weaning, or immediately upon arrival at the feedlot with a commercial bovine respiratory syncytial virus (BRSV) vaccine would reduce subsequent treatment for respiratory disease.

Bovine respiratory syncytial virus vaccination was associated with a significant (p<0.05) reduction in treatment rate in one of three groups of calves immunized prior to weaning (−12%) and in calves immunized upon arrival at the feedlot (−4%).

There was no significant (p>0.05) effect of the BRSV vaccine on treatment rate in calves immunized at weaning, in calves immunized upon arrival at the Saskatoon bull test station, or in yearlings immunized upon arrival at the feedlot.

Although the trend in these field trials was to a sparing effect of the BRSV vaccine, the small reduction in treatment rate may not justify the cost of the vaccination program.

     

The effect of subunit or modified live bovine herpesvirus-1 vaccines on the efficacy of a recombinant Pasteurella haemolytica vaccine for the prevention of respiratory disease in feedlot calves

The efficacy of a Pasteurella haemolytica vaccine (PhV) administered once to calves within 24 hours of arrival at a feedlot was tested for the ability to prevent morbidity and mortality from all bovine respiratory disease (BRD) and specifically from fibrinous pneumonia mortality. The PhV consisted of two immunizing ingredients: outer membrane proteins extracted from P. haemolytica, plus genetically attenuated leukotoxin produced by recombinant DNA technology. This double blind study was conducted at a large Saskatchewan feedlot using 2,324 high-risk calves purchased at auction markets and kept under typical commercial feedlot conditions. The trial design included four vaccine test groups: 1) PhV and a bovine herpesvirus type-1 (BHV-1) subunit vaccine comprised only of the virus glycoprotein IV (gIV); 2) PhV and a commercial modified live vaccine (MLV) containing BHV-1 and parainfluenza-3 viruses; 3) gIV alone; and 4) MLV alone. Calves were assigned to vaccine groups in a random systematic manner, individually identified, and monitored for 90 days after vaccination. The vaccines were given once, on arrival, to reflect common feedlot practice, although vaccination prior to expected risk would be more appropriate.

The PhV in combination with gIV reduced BRD morbidity by 20% (p < 0.05) compared to gIV alone and 24% (p < 0.05) compared to MLV alone, and reduced BRD mortality by 88% (p < 0.05) and fibrinous pneumonia mortality by 100% (p < 0.05) when compared to either gIV or MLV alone. Vaccination with PhV in combination with MLV significantly reduced the efficacy of the PhV in preventing BRD morbidity, BRD mortality, and fibrinous pneumonia mortality and also reduced the antibody response to P. haemolytica leukotoxin. These results suggest that the MLV interfered with the protective capacity of the PhV.

     

Efficacy of immunization of feedlot calves with a commercial Haemophilus somnus bacterin.

Two cohorts, consisting of 10,723 calves total, were identified in this prospective follow-up study to investigate whether immunization of auction market beef calves immediately upon arrival at the feedlot with a commercial Haemophilus somnus whole cell killed bacterin would reduce subsequent mortality. In addition to mortality rate, the use of incidence rate of fatal disease is introduced as an effect measure to examine vaccine efficacy in the feedlot. The Haemophilus somnus bacterin had no significant effect on the overall crude mortality rate; however, the bacterin appeared to significantly (p less than 0.05) reduce the incidence rate of fatal disease and the mortality rate during the first two months in the feedlot, when risk of fatal disease onset was highest. Once mortalities likely not associated with hemophilosis (for example, a fractured femoral neck) were removed from the analysis, steer mortality rate, but not heifer mortality rate, was reduced significantly (p less than 0.05) in the vaccinated group. The attributable percent overall for steers was 17.4%; this suggests that 17.4% of fatal respiratory disease in the unvaccinated steers could have been prevented by vaccination with the H. somnus bacterin. Heifer calves demonstrated a significantly (p less than 0.01) higher incidence rate of fatal disease during the first week than did steer calves, indicating that a different pattern of fatal disease existed for the two sexes. Use of a second vaccination two weeks after arrival did little to decrease mortality risk.     

Bovine coronavirus (BCV) infections in transported commingled beef cattle and sole-source ranch calves

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

Lesions and effects of location for administration of clostridial bacterin-toxoid vaccines on growth performance and eating and drinking behaviors in newly arrived calves at a feedlot

OBJECTIVES: To determine the effect of location for administration of clostridial vaccines on behavior, growth performance, and health of calves at a feedlot, the relative risk of calves developing an injection-site reaction or being misdiagnosed as having bovine respiratory disease complex (BRDC), and the percentage of subcutaneous injection-site reactions that were detectable on carcasses after the hides were removed. ANIMAL: 170 newly arrived calves at a feedlot. PROCEDURE: Eating and drinking behaviors of calves during the initial 57 days after arrival were observed at a commercial feedlot, using an electronic monitoring system. Calves were assigned randomly to receive a clostridial vaccine (base of ear or neck). Data on reactions at the injection site were collected. RESULTS: Mean daily gain (MDG) for the initial 57 days did not differ significantly between treatments. Risk of being misdiagnosed as having BRDC was not associated with location for administration of vaccine. Calves vaccinated in the base of the ear were at higher risk of having an injection-site reaction at day 57 or at slaughter. Eighty-nine percent (95% confidence interval, 52 to 100%) of injection-site reactions in the neck could not be located on the carcasses after hides were removed. Calves vaccinated in the neck drank significantly fewer times per day during the first 57 days than calves vaccinated in the base of the ear. CONCLUSIONS AND CLINICAL RELEVANCE: Location for administration of a clostridial vaccine did not significantly affect health, growth performance, or eating behavior. Most subcutaneous injection-site reactions were not detectable after the hide was removed.     

Effect of age at the time of vaccination on antibody titers and feedlot performance in beef calves

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

Comparison of two formulations of oxytetracycline given prophylactically to reduce the incidence of bovine respiratory disease in feedlot calves

A trial involving 1,803 feedlot calves was conducted under commercial feedlot conditions in western Canada to compare the relative effectiveness of a new oxytetracycline formulation, administered either intramuscularly (BMI) or subcutaneously (BMS), to a currently available oxytetracycline formulation, administered intramuscularly (LAB), for the prevention of bovine respiratory disease (BRD) in feedlot calves. All experimental treatments were administered upon arrival at the feedlot and again on the third day after arrival.

Over the entire feeding period, there were no significant differences (p≥0.05) in the BRD treatment rates or the BRD relapse rates between either the BMI or BMS groups compared to the LAB group. Similarly, there were no significant differences (p≥0.05) in the BRD treatment rates in the BMI or BMS groups from days 8-14, days 15-90, or days 1-90 of the feeding period compared to the LAB group. However, during the first seven days of the feeding period the BRD treatment rate in the BMI group was 1.55 times (p<0.05) higher than in the LAB group. From days 1-90 and day 1 to the end of the feeding period, the overall mortality rates, BRD mortality rates, and BRD case fatality rates were two to six times lower in the BMS and BMI groups as compared to the LAB group; however, these differences were not statistically significant (p≥0.05).

These data indicate that both the intramuscular and subcutaneous administration of a new oxytetracycline formulation are comparable to the intramuscular administration of a currently available oxytetracycline formulation when given to calves upon arrival at the feedlot.

     

A field trial of preshipment vaccination of calves

A field trial to investigate the efficacy of vitamins ADE, a Haemophilus somnus bacterin, a pasteurella bacterin, and two intranasal infectious bovine rhinotracheitis-parainfluenza type 3 vaccines administered to beef calves at least three weeks prior to weaning and shipment was conducted.

Over 1000 calves were vaccinated, but of the 692 calves shipped from the ranch of origin, only 276 calves were located in Ontario, or Quebec, feedlots. The average treatment rate was 30%. Neither vitamins ADE, H. somnus bacterin, pasteurella bacterin or the porcine tissue culture infectious bovine rhinotracheitis-parainfluenza type 3 vaccine had a significant effect on treatment rates for respiratory disease. Calves vaccinated with the temperature sensitive infectious bovine rhinotracheitis-parainfluenza type 3 vaccine had a significantly (p < 0.05) lower treatment rate than the nonvaccinated, and the porcine tissue culture infectious bovine rhinotracheitis-parainfluenza type 3 vaccinated, calves. Calves vaccinated with the temperature sensitive infectious bovine rhinotracheitis-parainfluenza type 3 vaccine did not have a significantly reduced treatment rate in comparison to nonvaccinated calves from the same source.

     

A live Pasteurella haemolytica vaccine efficacy trial

A live Pasteurella haemolytica serotype 1 vaccine was used in an efficacy trial conducted on 100 lightweight feeder calves purchased from a Florida ranch. Forty-one calves were inoculated with the vaccine intradermally in the neck. Fifty-nine calves served as nonvaccinated controls. Fourteen days later, the calves were shipped to an order buyer in eastern Tennessee, where the calves were mixed with 60 local calves in a community sale barn for 72 hours. After 3 additional days, the calves were shipped to a research feedlot in Bushland, Tex. They remained in the feedlot for 56 days, and the test was concluded 76 days after vaccination. The P haemolytica vaccine had no significant effect on performance, morbidity, or mortality. There was no significant difference between the vaccinated and nonvaccinated calves in the number of times Pasteurella was isolated. The calves became seropositive to bovine viral diarrhea virus, respiratory syncytial virus, and infectious bovine rhinotracheitis (IBR) virus during the 76-day experiment. All calves initially were seropositive to parainfluenza-3 virus. A virulent outbreak of IBR occurred 30 days after the calves arrived at the feedlot. Before the onset of IBR, the isolation of P haemolytica serotype 1 from nasal turbinates was rare (2 of 500 nasal swabs). After the IBR outbreak, P haemolytica serotype 1 was isolated from 40 of 92 calves.     

A comparison of florfenicol and tilmicosin for the treatment of undifferentiated fever in feedlot calves in western Canada

A field trial was performed under commercial feedlot conditions in western Canada to compare the efficacy of florfenicol and tilmicosin for the treatment of undifferentiated fever (UF) in calves that received metaphylactic tilmicosin upon arrival at the feedlot. One thousand and eighty recently weaned, auction market derived, crossbred beef calves suffering from UF were allocated to one of 2 experimental groups as follows: florfenicol, which was intramuscular (i.m.) florfenicol administered at the rate of 20 mg/kg body weight (BW) at the time of allocation (Day 0) and again 48 h later, or tilmicosin, which was subcutaneous (s.c.) tilmicosin administered once at the rate of 10 mg/kg BW on day 0. Five hundred and forty-four animals were allocated to the florfenicol group and 536 animals were allocated to the tilmicosin group. The chronicity, wastage, overall mortality, and bovine respiratory disease (BRD) mortality rates were significantly (P < 0.05) lower in the florfenicol group than in the tilmicosin group. There were no significant (P > or = 0.05) differences in first UF relapse, second UF relapse, hemophilosis mortality, or miscellaneous mortality rates between the florfenicol and tilmicosin groups. Average daily gain (ADG) from arrival at the feedlot to the time of implanting and ADG from allocation to the time of implanting were significantly (P < 0.05) lower in the florfenicol group as compared with the tilmicosin group. There were no significant (P > or = 0.05) differences in arrival weight, allocation weight, implanting weight, or ADG from arrival to allocation between the experimental groups. In the economic analysis, there was an advantage of $18.83 CDN per animal in the florfenicol group. The results of this study indicate that florfenicol is superior to tilmicosin for the treatment of UF because of lower chronicity, wastage, overall mortality, and BRD mortality rates. However, interpretation of these observations must take into consideration the fact that these calves received meta-phylactic tilmicosin upon arrival at the feedlot, which is a standard, cost-effective, management procedure utilized by feedlots in western Canada.     

Meta-analysis of field trials of antimicrobial mass medication for prophylaxis of bovine respiratory disease in feedlot cattle

One hundred and seven field trials of prophylactic mass medication for bovine respiratory disease (BRD) in feedlot cattle were reviewed. Meta-analysis is the formal quantitative statistical review process that was used to synthesize the data from randomized field trials and draw conclusions concerning the efficacy of prophylactic mass medication in feedlot calves.

The results of the meta-analysis indicated that prophylactic parenteral mass medication of calves with long-acting oxytetracycline or tilmicosin on arrival at the feedlot would reduce BRD morbidity rates (p < 0.001). There were, however, unreliable data on the effects of mass medication on mortality rates and performance, insufficient data on the most effective treatment regimes, and no valid data on the efficacy of feed and water medication for prophylaxis of BRD.

This review highlights the gaps in our knowledge and points out the need for additional well-designed randomized controlled field trials of adequate size to assess the efficacy and socioeconomic impact of prophylactic mass medication for BRD in feedlot cattle.

     

A comparison of florfenicol and tulathromycine for the treatment of undifferentiated fever in feedlot calves

The purpose of this study was to compare the relative cost-effectiveness of florfenicol with that of tulathromycin for treatment of undifferentiated fever (UF) in feedlot calves at ultra-high risk of developing UF that receive metaphylactic tulathromycin on arrival at the feedlot. Calves that received therapeutic florfenicol had lower overall mortality (P=.045) and bovine respiratory disease mortality (P=.050) compared with calves that received therapeutic tulathromycin, but no significant differences were detected in feedlot performance, carcass characteristics, or other animal health variables. There was a net advantage of Can$41.19/treated animal in the florfenicol group versus the tulathromycin group. This study demonstrates that it is more cost-effective to use florfenicol than tulathromycin for the initial treatment of UF in feedlot calves at ultra-high risk of developing UF that receive on-arrival metaphylactic tulathromycin.     

A comparison of prophylactic efficacy of tilmicosin and a new formulation of oxytetracycline in feedlot calves

Two replicated-pen field studies were performed under commercial feedlot conditions in western Canada to compare the administration of long-acting oxytetracycline at 30 mg/kg body weight (BW) versus tilmicosin at 10 mg/kg BW to feedlot calves upon arrival at the feedlot. Ten thousand nine hundred and eighty-nine, recently weaned, auction market derived, crossbred beef steer and bull calves were randomly allocated upon arrival at the feedlot to one of 2 experimental groups as follows: oxytetracycline, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at a rate of 30 mg/kg BW; or tilmicosin, which received subcutaneous tilmicosin (300 mg/mL formulation) at a rate of 10 mg/kg BW. There were 20 pens in each experimental group. In Study 1 and in the combined analysis, the initial undifferentiated fever (UF) treatment rate was significantly (P < 0.05) higher in the oxytetracycline group as compared with the tilmicosin group. There were no significant (P > or = 0.05) differences in first UF relapse, second UF relapse, third UF relapse, overall chronicity, overall rail, overall mortality, bovine respiratory disease (BRD) mortality, hemophilosis mortality, arthritis mortality, or miscellaneous mortality rates between the experimental groups in either study or in the combined analysis. In addition, there were no significant (P > or = 0.05) differences in initial weight, final weight, weight gain, days on feed, daily dry matter intake, average daily gain, or the dry matter intake to gain ratio between the experimental groups in either study or in the combined analyses. In the economic analysis, there was a net economic advantage of $5.22 CDN per animal in the oxytetracycline group, due to a lower prophylactic cost, even though the UF therapeutic cost was higher.     

The effect of route and dosage of immunization on the serological response to a Pasteurella haemolytica and Haemophilus somnus vaccine in feedlot calves

The effect of route and dosage of administration on the serological response to a vaccine containing genetically attenuated leukotoxin of Pasteurella haemolytica combined with bacterial extracts of P. haemolytica and Haemophilus somnus (Somnu-Star Ph, Biostar Inc., Saskatoon, Saskatchewan) was evaluated in a controlled field trial in 301 feedlot calves. Vaccination of calves on arrival at the feedlot with Somnu-Star Ph significantly (p < 0.05) increased P. haemolytica and H. somnus serum antibody titers and reduced bovine respiratory disease (BRD) morbidity. A single subcutaneous vaccination with Somnu-Star Ph was as effective in stimulating a humoral antibody response and in reducing BRD morbidity as double vaccination by the intramuscular or the subcutaneous route. Furthermore, there were no swellings or adverse reactions observed with either subcutaneous or intramuscular administration of Somnu-Star Ph.

These results suggest that feedlot calves can be immunized subcutaneously once on arrival with Somnu-Star Ph. Double vaccination was of no added value in this trial, because the majority of BRD morbidity occurred prior to revaccination fourteen days postarrival. Additional larger-sized field trials are needed to monitor the duration of immunity following vaccination and to test the effect of route and dosage of vaccination on mortality.

     

Effects of 3-methylindole production and immunity against bovine respiratory syncytial virus on development of respiratory tract disease and rate of gain of feedlot cattle

OBJECTIVE: To determine whether immunity against bovine respiratory syncytial virus (BRSV) mitigates the effects of 3-methylindole (3MI) on occurrence of bovine respiratory tract disease (BRD) and rate of gain in feedlot cattle. ANIMALS: 254 mixed-breed beef cattle. PROCEDURE: Cattle were randomly assigned to 1 of 3 groups at the time of arrival at the feedlot. One group was vaccinated with an inactivated BRSV vaccine, another was vaccinated with a modified-live BRSV vaccine, and the third was maintained as unvaccinated control cattle. On days 0 and 28, serum BRSV antibody concentrations were measured, using serum neutralizing and ELISA techniques. Serum 3MI concentrations were measured at feedlot arrival and 3 days later. Cattle were monitored for development of BRD. At slaughter, lungs were evaluated grossly for chronic lesions. RESULTS: Higher serum 3MI concentrations early in the feeding period were associated with lower mean daily gain. Control cattle were more likely to be treated for BRD after day 3, compared with cattle vaccinated with the modified-live BRSV vaccine. Humoral immunity against BRSV did not appear to modify the effect of 3MI on development of BRD or mean daily gain. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that abrogating the effects of 3MI and BRSV infection may improve the health and growth performance of feedlot cattle. However, in this study, immunity against BRSV did not appear to protect against the potential synergism between 3MI and BRSV infection, possibly because of the slow rates of gain of cattle included in the study or timing of sample collection.     

A comparison of 2 vaccination programs in feedlot calves at ultra-high risk of developing undifferentiated fever/bovine respiratory disease

The aim of this study was to compare 2 vaccination programs in feedlot calves at ultra-high risk of developing undifferentiated fever (UF)/bovine respiratory disease (BRD). At feedlot arrival, 3882 calves were enrolled in the study and randomly allocated to 2 groups, which were housed by group in 12 pens. At the time of allocation, 1 group (MLV3-BT2) received a multivalent, modified-live viral vaccine containing infectious bovine rhinotracheitis virus (IBRV) and types I and II bovine viral diarrhea virus (BVDV), as well as a Mannheimia haemolytica (MH) and Pasteurella multocida bacterin-toxoid. The other group (MLV4-BT1) received a vaccine containing IIBRV, type I BVDV, bovine respiratory syncytial virus, and parainfluenza-3 virus, as well as a MH bacterin-toxoid. At an average of 69 days post arrival, the groups received their respective viral vaccines. The initial UF treatment, overall chronicity, overall wastage, overall mortality, and BRD mortality rates were significantly (P < 0.05) lower in the MLV3-BT2 group than in the MLV4-BT1 group. Average daily gain and the proportions of yield grade Canada 3 and quality grade E carcasses were significantly (P < 0.05) higher in the MLV3-BT2 group than in the MLV4-BT1 group. No significant (P > or = 0.05) difference in the dry matter intake to gain ratio was detected between the 2 groups. In economic terms, there was a net advantage of $20.86 CDN/animal in the MLV3-BT2 group. This study demonstrates that it is more cost effective to use an MLV3-BT2 vaccination program than a MLV4-BT1 vaccination program in feedlot calves at ultra-high risk of developing UF/BRD.     

Transmission of bovine coronavirus and serologic responses in feedlot calves under field conditions

OBJECTIVE: To compare shedding patterns and serologic responses to bovine coronavirus (BCV) in feedlot calves shipped from a single ranch in New Mexico (NM calves) versus calves assembled from local sale barns in Arkansas (AR calves) and to evaluate the role of BCV on disease and performance. ANIMALS: 103 feedlot calves from New Mexico and 100 from Arkansas. PROCEDURES: Calves were studied from before shipping to 35 days after arrival at the feedlot. Nasal swab specimens, fecal samples, and serum samples were obtained before shipping, at arrival, and periodically thereafter. Bovine coronavirus antigen and antibodies were detected by use of an ELISA. RESULTS: NM calves had a high geometric mean titer for BCV antibody at arrival (GMT, 1,928); only 2% shed BCV in nasal secretions and 1% in feces. In contrast, AR calves had low antibody titers against BCV at arrival (GMT, 102) and 64% shed BCV in nasal secretions and 65% in feces. Detection of BCV in nasal secretions preceded detection in feces before shipping AR calves, but at arrival, 73% of AR calves were shedding BCV in nasal secretions and feces. Bovine coronavirus infection was significantly associated with respiratory tract disease and decreased growth performance in AR calves. CONCLUSIONS AND CLINICAL RELEVANCE: Replication and shedding of BCV may start in the upper respiratory tract and spread to the gastrointestinal tract. Vaccination of calves against BCV before shipping to feedlots may provide protection against BCV infection and its effects with other pathogens in the induction of respiratory tract disease.     

Effect of intranasal vaccination against bovine enteric coronavirus on the occurrence of respiratory tract disease in a commercial backgrounding feedlot

OBJECTIVE: To measure antibody titers against bovine coronavirus (BCV), determine frequency of BCV in nasal swab specimens, and compare calves treated for bovine respiratory tract disease (BRD) between those given an intranasally administered vaccine and control calves. DESIGN: Randomized clinical trial. ANIMALS: 414 heifer calves. PROCEDURE: Intranasal BCV antigen concentration and antibody titer against BCV were measured on entry to a feedlot. Calves were randomly assigned to receive 3.0 mL of a modified-live virus vaccine against bovine enteric coronavirus and rotavirus or 3.0 mL of saline (0.9% NaCl) solution. Calves were confined to 1 of 2 pens, depending on vaccination status, for a minimum of 17 days of observation (range, 17 to 99). Selection of calves for treatment of BRD and scoring for severity of disease were done by veterinarians unaware of treatment status. RESULTS: Intranasal BCV (125/407 [31%]) and serum antibody titers > or = 20 against BCV (246/396 [62%]) were identified in calves entering the feedlot. Vaccination was associated with significant decrease in risk of treatment for BRD; intranasal BCV on entry to the feedlot was associated with increased risk of treatment. Univariate analysis revealed that control calves with intranasal BRD on entry to the feedlot and those with antibody titer < 20 were significantly more likely to be treated for BRD. CONCLUSIONS AND CLINICAL RELEVANCE: These data provide further evidence of an association between BCV and respiratory tract disease in feedlot calves. An intranasally administered vaccine appeared to reduce risk of treatment for BRD.