Effects of tilmicosin phosphate, administered prior to transport or at time of arrival, and feeding of chlortetracycline, after arrival in a feedlot, on Mannheimia haemolytica in nasal secretions of transported steers

OBJECTIVE: To determine effects of time of administration of tilmicosin and feeding of chlortetracycline on colonization of the nasopharynx of transported cattle by Mannheimia haemolytica (MH). ANIMALS: 454 steers (body weight, 200 kg). PROCEDURE: 3 studies included 4 truckloads of steers assembled and processed in the southeastern United States. For each truckload of steers, a third received tilmicosin before transportation (PRIOR), then all were transported to a feedlot in New Mexico (23 hours). At arrival (day 0), another third received tilmicosin (ARR). The remaining third did not receive tilmicosin (control steers [CTR]). Steers in studies 1 and 2 were housed in a feedlot, and steers in study 3 were housed on wheat pasture. One half of the steers from each group in studies 2 and 3 were fed chlortetracycline on days 5 to 9. Steer with signs of respiratory tract disease were treated. Nasal swab specimens were examined for MH to determine colonization. RESULTS: PRIOR and ARR steers had a lower incidence of respiratory tract disease and MH colonization than CTR steers, but PRIOR and ARR steers did not differ. Feeding chlortetracycline did not have an effect. CONCLUSIONS AND CLINICAL RELEVANCE: Tilmicosin can inhibit MH from colonizing the nasopharynx of cattle. Because tilmicosin inhibits the growth of MH in the respiratory tract, medication with tilmicosin prior to transport should reduce the incidence of acute respiratory tract disease during the first week at the feedlot when calves are most susceptible to infectious organisms.     

Colonization of the tonsils of calves with Pasteurella haemolytica.

Tonsils of 10 calves were inoculated with Pasteurella haemolytica (PH) and the degree of colonization was followed by collecting sequential tonsil. wash specimens. Tonsils were colonized for at least 3 weeks after instillation of PH into the tonsillar sinus. Calves with colonized tonsils responded with serum and nasal secretion antibody responses to PH and to leukotoxin. Pasteurella haemolytica was detected in nasal mucus specimens of 2 calves during the week after inoculation of the tonsils, but all other specimens were culture-negative. Infectious bovine rhinotracheitis virus-induced respiratory tract disease 25 days later did not elicit a population increase of PH in the tonsils, and did not elicit shedding of PH in nasal mucus.     

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.     

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.     

Conglutinin and immunoconglutinin titers in stressed calves in a feedlot

OBJECTIVE: To determine whether increased conglutinin titers are evident in stressed calves that do not develop respiratory tract disease in feedlots, compared with respiratory tract disease, and to determine the increase in immunoconglutinin titers. ANIMALS: 101 mixed-breed beef calves. PROCEDURE: Calves were processed at 4 farms of origin and allowed to remain with their dams for another 100 days. Calves from each farm were brought to a centrally located order-buyer barn. In a feedlot, 101 calves were assigned to pens and observed daily for clinical signs of acute respiratory tract disease. When sick calves were detected, they were treated with antibiotics and isolated in a pen for 4 days. Conglutinin and immunoconglutinin titers were determined for all calves. RESULTS: During the 28-day study, 73 calves developed respiratory tract disease, whereas 28 calves remained healthy. Mean conglutinin titers differed significantly among calves from the 4 farms. Significant differences were not detected in conglutinin titers among calves on the basis of sex, morbidity, or vaccination status against Mannheimia haemolytica at each farm, the order-buyer barn, or the feedlot on days 8, 15, and 28 after arrival. Immunoconglutinin titers in calves differed significantly among farms and morbidity status. CONCLUSIONS AND CLINICAL RELEVANCE: Mean conglutinin titers in calves do not appear to be associated with the incidence of acute respiratory tract disease; however, increased immunoconglutinin titers appear to be associated with recovery of stressed calves from respiratory tract disease during the first 15 days after arrival in a feedlot.     

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.     

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.     

Association between infection of the respiratory tract attributable to bovine coronavirus and health and growth performance of cattle in feedlots

OBJECTIVE: To determine the association between respiratory tract infection with bovine coronavirus (BCV), treatment for respiratory tract disease, pulmonary lesions at slaughter, and average daily gain in cattle in feedlots. ANIMALS: 837 calves in feedlots in Ohio and Texas. PROCEDURE: Nasal swab specimens were obtained from cattle at arrival in a feedlot (day 0) and at various times during the initial 28 days after arrival. Specimens were tested for BCV, using an antigen-capture ELISA. Serum samples were obtained at arrival and again 28 days after arrival and tested for antibodies to BCV, using an antibody-detection ELISA. Information was collected regarding treatment for cattle with respiratory tract disease and average daily gain during the feeding period. Pulmonary lesions were evaluated at slaughter. RESULTS: Cattle shedding BCV from the nasal cavity and developing an antibody response against BCV were 1.6 times more likely to require treatment for respiratory tract disease than cattle that did not shed the virus or develop an immune response against BCV. Additionally, cattle that shed BCV from the nasal cavity were 2.2 times more likely to have pulmonary lesions at slaughter than cattle that did not shed the virus. The BCV shedding or seroconversion status did not affect average daily gain. CONCLUSIONS AND CLINICAL RELEVANCE: Bovine coronavirus infects feedlot cattle and is associated with an increased risk for cattle developing respiratory tract disease and pulmonary lesions. Development of appropriate control measures could help reduce the incidence of respiratory tract disease.     

Relationship of vitamin E supplementation and antimicrobial treatment with acute-phase protein responses in cattle affected by naturally acquired respiratory tract disease

OBJECTIVE: To correlate serum concentrations of fibrinogen (Fib), haptoglobin (Hap), serum amyloid-A (SAA), and alpha-1 acid glycoprotein (AGP) with clinical respiratory tract disease and response to treatment in transport-stressed feedlot cattle fed vitamin E-supplemented diets. ANIMALS: 387 heifer calves (mean initial weight, 197 kg). PROCEDURE: Calves purchased from an order buyer were delivered to a feedlot to study the effects of dietary supplementation with 2,000 IU of vitamin E for 0, 7, 14, or 28 days after arrival. Serum or plasma Fib, Hap, SAA, and AGP concentrations were measured on days 0, 7, and 28 after arrival as well as at the time of treatment for respiratory tract disease with antimicrobial drugs and after completion of treatment. RESULTS: Vitamin E supplementation was associated with decreased treatment costs. In cattle that were not recognized as sick or responded positively to 1 antimicrobial treatment, serum Hap concentrations were significantly lower on days 0 and 7 than concentrations for cattle that required > 1 treatment. Serum Hap concentrations and ratios of Hap to SAA on day 0 significantly correlated with the number of antimicrobial treatments required. Serum Hap concentrations at the time of initial treatment were significantly lower for cattle that required only 1 treatment, compared with those that required > 1 treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Serum Hap concentrations are of potential value for use in assessing feedlot cattle that may become ill as a result of respiratory tract disease and for use in monitoring treatment efficacy.     

Efficacy of tulathromycin compared with tilmicosin and florfenicol for the control of respiratory disease in cattle at high risk of developing bovine respiratory disease

Three studies conducted at feedlots in Colorado, Idaho, and Texas examined the comparative efficacy of tulathromycin injectable solution for the treatment of cattle at high risk of developing undifferentiated bovine respiratory disease (BRD). Each study randomly allocated 250 calves to receive tulathromycin at 2.5 mg/kg and 250 calves to receive either tilmicosin at 10 mg/kg (Colorado site) or florfenicol at 40 mg/kg (Idaho and Texas sites) on arrival at the feedlot. Calves were housed by treatment group in pens with 50 calves/pen. Beginning 3 days after antimicrobial treatment, cattle were observed for signs of BRD daily until harvest. In all three studies, the treatment success rates at 28 days after treatment and at harvest were significantly higher (P < or = .013) for cattle treated with tulathromycin than for cattle treated with either tilmicosin or florfenicol. Fewer tulathromycin-treated cattle were removed from the group as "chronics" or "mortalities" at 28 days posttreatment (P < or = .014) in all three studies. Tulathromycin demonstrated superior efficacy compared with tilmicosin and florfenicol when treating groups of high-risk cattle before the onset of signs of BRD.     

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.     

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.     

Isolation of respiratory bovine coronavirus, other cytocidal viruses, and Pasteurella spp from cattle involved in two natural outbreaks of shipping fever

OBJECTIVE: To identify cytocidal viruses and Pasteurella spp that could be isolated from cattle involved in 2 natural outbreaks of shipping fever. ANIMALS: 105 and 120 castrated male 4- to 8-month-old feedlot cattle involved in 1997 and 1998 outbreaks, respectively. PROCEDURES: Nasal swab specimens and blood samples were collected, and cattle were vaccinated on arrival at an order-buyer barn from 4 local auction houses. Four days later, they were transported to a feedlot, and additional nasal swab specimens and blood samples were collected. Nasal swab specimens were submitted for virus isolation and bacterial culture; blood samples were submitted for measurement of respiratory bovine coronavirus (RBCV) hemagglutinin inhibition titers. RESULTS: 93 of 105 cattle and 106 of 120 cattle developed signs of respiratory tract disease during 1997 and 1998, respectively, and RBCV was isolated from 81 and 89 sick cattle, respectively, while at the order-buyer's barn or the day after arrival at the feedlot. During the 1997 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 4 cattle 14 days after arrival at the feedlot. During the 1998 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and on arrival at the feedlot and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 1 animal the day of, and from 18 cattle 7 and 14 days after, arrival at the feedlot. Pasteurella spp was cultured from 4 and 6 cattle at the order-buyer's barn and from 92 and 72 cattle on arrival at the feedlot during the 1997 and 1998 outbreaks, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that RBCV may play a causative role in outbreaks of shipping fever in cattle. More than 80% of the sick cattle shed RBCV at the beginning of 2 outbreaks when the Pasteurella spp infection rate was low.     

Prophylactic tilmicosin medication of feedlot calves at arrival

The parenteral administration of the antibiotic tilmicosin given on arrival at a feedlot was evaluated in a group of 304 steer calves. These calves were allotted to 24 pens so that there were 12 replicates of both the control and medicated groups. The treatment rate was reduced significantly during the first five days (p < 0.05) and during the first month (p < 0.01) of the feeding period in the medicated group. The average days from arrival until first treatment for respiratory disease was increased to 21 days in the medicated group compared to 9 days (p < 0.01) for the controls. The medicated group had improved average daily gain (p < 0.01) and feed efficiency (p < 0.01) over the trial period when compared to the nonmedicated animals.     

Effect of danofloxacin and tilmicosin on body temperatures of beef calves with pneumonia experimentally induced by inoculation with Mannheimia haemolytica

OBJECTIVE: To examine effects of danofloxacin and tilmicosin on continuously recorded body temperature in beef calves with pneumonia experimentally induced by inoculation of Mannheimia haemolytica. ANIMALS: 41 Angus-cross heifers (body weight, 160 to 220 kg) without a recent history of respiratory tract disease or antimicrobial treatment, all from a single ranch. PROCEDURE: Radiotransmitters were implanted intravaginally in each calf. Pneumonia was induced intrabronchially by use of logarithmic-phase cultures of M. haemolytica. At 21 hours after inoculation, calves were treated with saline (0.9% NaCl) solution, danofloxacin, or tilmicosin. Body temperature was monitored from 66 hours before inoculation until 72 hours after treatment. Area under the curve (AUC) of the temperature-time plot and mean temperature were calculated for 3-hour intervals and compared among treatment groups. RESULTS: The AUCs for 3-hour intervals did not differ significantly among treatment groups for any of the time periods. Analysis of the mean temperature for 3-hour intervals revealed significantly higher temperatures at most time periods for saline-treated calves, compared with temperatures for antimicrobial-treated calves; however, we did not detect significant differences between the danofloxacin- and tilmicosin-treated calves. The circadian rhythm of temperatures before exposure was detected again approximately 48 hours after bacterial inoculation. CONCLUSIONS AND CLINICAL RELEVANCE: Danofloxacin and tilmicosin did not differ in their effect on mean body temperature for 3-hour intervals but significantly decreased body temperature, compared with body temperature in saline-treated calves. Normal daily variation in body temperature must be considered in the face of respiratory tract disease during clinical evaluation of feedlot cattle.     

Prophylactic medication of feedlot calves with tilmicosin

The parenteral administration to calves of the antibiotic tilmicosin either on arrival at a feedlot or 72 hours later was evaluated in a group of 308 steer calves. The calves were allotted to 24 pens so that there were eight replicates of the two medicated groups and eight replicates of the control group. The need for veterinary treatment was reduced significantly (P less than 0.05) during the first month of the feeding period in the two medicated groups. The medicated groups had an improved average daily weight gain (P less than 0.01) over the trial period compared with the non-medicated animals. This improved average daily gain by the medicated groups was not reduced when animals with respiratory disease were excluded from the calculations. The medicated groups also had an improved feed conversion efficiency (P less than 0.01) over the first 60 days of the feeding period compared with the non-medicated animals.     

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.

     

Antibody titers against bovine coronavirus and shedding of the virus via the respiratory tract in feedlot cattle

OBJECTIVE: To describe patterns of seroconversion to bovine coronavirus (BCV) and shedding of BCV from the respiratory tract in feedlot cattle. ANIMALS: 1,074 calves in feedlots in Ohio, Texas, and Nebraska. PROCEDURE: Nasal swab specimens were obtained at time of arrival (day 0) and at various times during the initial 28 days after arrival at feedlots. Specimens were tested for BCV, using an antigen-capture ELISA. Serum samples were obtained at time of arrival and again 28 days after arrival; sera were analyzed for antibodies to BCV, using an antibody-detection ELISA. RESULTS: Samples from 12 groups of cattle entering 7 feedlots during a 3-year period revealed that 78 of 1,074 (7.3%) cattle were shedding BCV (range, 0 to 35.9% within specific groups). At time of arrival, 508 of 814 (62.4%) cattle had low (< 50) or undetectable BCV antibody titers. Seroconversion to BCV during the initial 28 days after arrival was detected in 473 of 814 (58%) cattle tested (range, 20.3 to 84.1 % within specific groups). In cattle shedding BCV from the nasal passages, 49 of 68 (72.1 %) seroconverted, and 472 of 746 (63.3%) cattle that were not shedding the virus seroconverted. CONCLUSIONS AND CLINICAL RELEVANCE: Bovine coronavirus can be detected in populations of feedlot cattle in the form of viral shedding as well as seroconversion to the virus. Although only a few cattle were shedding the virus at the time of arrival at a feedlot, most of the cattle seroconverted to BCV by 28 days after arrival.     

Single-dose treatment of neonatal calf pneumonia with the new macrolide antibiotic tilmicosin

Tilmicosin, a new macrolide antibiotic, 20-deoxo-20-(3,5-dimethylpiperidin-l-yl)desmycosin, formerly identified as EL-870, has been evaluated in three experiments as a single subcutaneous injection at dosages of 10, 20 or 30 mg/kg for the treatment of naturally occurring pneumonia in neonatal calves. Male Holstein calves, under five days of age, were shipped from Wisconsin and housed in pens. They were assigned sequentially to a treatment group when their temperature was greater than or equal to 39.7 degrees C for two consecutive days or greater than or equal to 39.7 degrees C and signs of respiratory disease were present. Clinical signs were evaluated daily for 14 days after the tilmicosin treatment. Calves that died and those that survived for the 14 day experimental period were examined post mortem. Treatment with tilmicosin was effective at all dosage levels, as determined by significant (P less than or equal to 0.05) reductions in body temperature within 24 hours, in the number of animals that died, in the incidence and severity of clinical signs, in the number of Pasteurella species found in lung tissue and in the severity of the pneumonic lesions. In two of the three experiments severe outbreaks of cryptosporidiosis resulted in significant mortalities within a few days after the arrival of the calves. Treatment with tilmicosin was effective against respiratory disease even in the presence of this severe concurrent disease.     

Effects of Metaphylactic Antibiotics on Behavior of Feedlot Calves

Three 21-d trials were conducted at a commercial feedlot near Wellton, Arizona to determine the effects of metaphylactic injectable antibiotics on feeding and watering behavior and on animal health and growth performance of feedlot calves. Newly received male calves (n = 150, 150, and 148 for Trials 1, 2, and 3, respectively) were randomly assigned to one of four treatments: 1) no injectable antibiotic (control), 2) tilmicosin (TIL) subcutaneously (s.c.) 3) florfenicol i.m. (FIM), or 4) florfenicol s.c. (FSC). Throughout the 21-d trials, calves were observed and documented as morbid or healthy. Daily feeding and watering behaviors were collected for trials 2 and 3. A smaller (P=0.001) percentage of TIL, FIM, and FSC calves were identified as morbid (average, 27%) compared with control calves (47%), and ADG was greater (P=0.04) for TIL, FIM, and FSC calves (average, 0.42 kg/d) than for control calves (0.23 kg/d). Calves castrated before arrival had greater (P=0.001) ADG (0.53 vs 0.21 kg/d) and lower (P=0.05) mortality (0 vs 3.5%) during the first 21 d than did calves castrated upon arrival at the feedlot. Calves that remained healthy had greater (P=0.001) ADG than did calves that became morbid (0.78 vs−0.03 kg/d). Calves treated with TIL, FIM, or FSC had increased (P=0.02) feeding bouts per day in Trial 3 compared with control calves (average, 11 vs 9 bouts/d). Total feeding time was increased (P=0.005) for FIM calves compared with control, TIL, and FSC calves in Trial 3. No differences (P>0.10) were observed in watering behavior because of antibiotic treatment. Metaphylactic injectable antibiotics administered upon calves’ arrival at the feedlot did not reduce the total time newly received feedlot calves spent feeding, decreased the incidence of morbidity by 43%, and improved growth performance during the 21-d receiving period.