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.

Microbiological and histopathological findings in cases of fatal bovine respiratory disease of feedlot cattle in Western Canada.

The aim of this study was to describe the microbiologic agents and pathologic processes in fatal bovine respiratory disease (BRD) of feedlot cattle and to investigate associations between agents and pathologic processes. Ninety feedlot calves diagnosed at necropsy with BRD and 9 control calves without BRD were examined, using immunohistochemical (IHC) staining and histopathologic studies. Mannheimia haemolytica (MH) (peracute, acute, and subacute cases) and Mycoplasma bovis (MB) (subacute, bronchiolar, and chronic cases) were the most common agents identified in fatal BRD cases. Significant associations (P < 0.10) were detected between microbiologic agents and between agents and pathologic processes. When IHC staining was used, 25/26 (96%) of animals that were positive for bovine viral diarrhea virus (BVDV) were also positive for MH; 12/15 (80 %) of animals that were positive for Histophilus somni (HS) were also positive for MB; and all of the animals that were positive for HS were negative for MH and BVDV. This quantitative pathological study demonstrates that several etiologic agents and pathologic processes are involved in fatal BRD of feedlot cattle.

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.

Evaluation of the efficacy of tulathromycin as a metaphylactic antimicrobial in feedlot calves.

The purpose of this study was to determine the efficacy and cost-effectiveness of tulathromycin (DRAX) versus tilmicosin (MIC) or oxytetracycline (TET) as a metaphylactic antimicrobial in feedlot calves. Calves that received DRAX had significantly (P<.05) lower initial undifferentiated fever (UF) treatment and relapse rates; lower overall chronicity, overall mortality, and cause-specific mortality rates; higher average daily gains; and improved quality grades. However, calves that received DRAX also had poorer (P<.05) yield grades compared with calves that received MIC or TET and worse feed conversion compared with calves that received MIC. Net advantages in the DRAX group were 3.79CanDollars/animal and 16.96CanDollars/animal compared with the MIC and TET groups, respectively. Based on these results, DRAX is a more efficacious and cost-effective metaphylactic antimicrobial than MIC or TET in feedlot calves at ultra-high risk of developing UF. In addition, this study presents a comparison between two methods ("deads out" and "deads in") of calculating feedlot performance variables.

An evaluation of the relative efficacy of tulathromycin for the treatment of undifferentiated fever in feedlot calves in Nebraska.

A field trial was performed under commercial feedlot conditions in central Nebraska to assess the relative efficacy of tulathromycin (TULA) to florfenicol (FLOR) for the treatment of undifferentiated fever (UF) in feedlot calves that did not receive a metaphylactic antimicrobial or vaccines/bacterins containing Mannheimia haemolytica or Histophilus somni at feedlot arrival by comparing animal health, feedlot performance, and carcass characteristic variables. Two hundred recently weaned, auction market derived, crossbred beef calves that met the study-specific case definition of UF were randomly allocated in a 1:1 ratio to 1 of 2 experimental groups as follows: TULA, which received tulathromycin administered subcutaneously at the rate of 2.5 mg/kg body weight (BW) once at the time of allocation; or FLOR, which received florfenicol administered subcutaneously at the rate of 40 mg/kg BW once at the time of allocation. In terms of animal health, the first UF relapse (RR = 0.65), overall mortality (RR = 0.33), and BRD mortality (RR = 0.29) rates in the TULA group were significantly (P < 0.05) lower than in the FLOR group. There were no significant (P > or = 0.05) differences between the TULA and FLOR groups for the other animal health variables measured. There was no significant (P > or = 0.05) difference in average daily gain between the TULA and FLOR groups. There were no significant (P > or = 0.05) differences in the overall distributions of quality grade and yield grade between the experimental groups; however, a significantly (P < 0.05) higher proportion of carcasses in the TULA group graded yield grade USDA-4 as compared with the FLOR group. In the economic analysis, the benefits observed resulted in an economic advantage of $52.50 USD/animal in the TULA group due to lower first UF relapse and overall mortality rates, even though the occurrence of yield grade USDA-4 carcasses increased and the initial UF treatment cost was higher.

An evaluation of the metaphylactic effect of ceftiofur crystalline free Acid in feedlot calves.

The relative effect of metaphylactic ceftiofur crystalline free acid (CCFA) versus metaphylactic tilmicosin was evaluated in beef calves under commercial feedlot conditions in Nebraska. At feedlot arrival, 11,605 animals at ultrahigh risk of developing bovine respiratory disease (BRD) were allocated to one of three experimental groups: CCFA-3 (6.6 mg/kg SC), CCFA-7 (6.6 mg/kg), or TILM-3 (tilmicosin, 10 mg/kg SC). Animals were eligible for subsequent BRD treatment 3 (CCFA-3 and TILM-3 groups) or 7 (CCFA-7 group) days later. Compared with the TILM-3 group, overall chronicity, overall mortality, BRD mortality, and metabolic mortality rates were significantly (P < .05) lower in the CCFA-3 and CCFA-7 groups; average daily gain was significantly (P < .05) higher in the CCFA-3 group; the proportion of quality grade No Roll carcasses was significantly (P < .05) lower in the CCFA-3 and CCFA-7 groups; and there were per-animal advantages of 22.05 dollars and 18.98 dollars in the CCFA-3 and CCFA-7 groups, respectively. In beef calves at ultrahigh risk of developing BRD, it is more cost effective to administer metaphylactic CCFA than tilmicosin at feedlot arrival.

Determination of the seroprevalence of Neospora caninum in feedlot steers in Alberta.

A study was conducted in Alberta to determine the seroprevalence of Neospora caninum in feedlot calves purchased from various auction markets throughout western Canada. Four feedlots (1 feedlot from each of the Airdrie and High River areas and 2 feedlots from the Strathmore area) were selected for sampling. At each feedlot, a random 10% sample of feedlot steer and bull calves entering the feedlot from September 2001 to December 2001 were enrolled in the study until there were a maximum of 500 animals enrolled per feedlot. Blood samples were collected from 1976 male animals at the time of entry to the 4 study feedlots. The animals represented 375 groups purchased from 70 sale points throughout British Columbia, Alberta, Saskatchewan, and Manitoba. Of the 1976 animals tested, 128 animals tested positive for antibodies to N. caninum. The prevalence and adjusted 95% confidence limits for N. caninum in beef calves on entrance to the feedlot in western Canada were 6.5% (95% CI, 5.1 to 8.2). There were no significant (P > or = 0.05) associations between the risk of treatment, the risk of designation as "chronic," and the risk of death and antibodies to N. caninum either before or after adjusting for feedlot, entry weight, entry date, and clustering of disease within lots at each feedlot. In addition, there was no significant (P > or = 0.05) association between serological status and feedlot entry weight or average daily gain. Note that there was no information available on feed conversion because the calves were mixed within existing commercial feedlot pens and the actual feed intake of each animal could not be determined. Adjustment for the concentration of antibodies to bovine viral diarrhea virus on arrival did not change any of the examined associations between N. caninum status and calf health or performance. The results of this study demonstrated that the prevalence of N. caninum in feedlot calves in western Canada was less than the prevalence reported in the United States. Additional studies are required to determine whether the inferior rate of gain and feed efficiency observed in the southern United States with animals testing positive for antibodies to N. caninum also occurs under the management conditions used in western Canada.