The association between serological titers in infectious bovine rhinotracheitis virus, bovine virus diarrhea virus, parainfluenza-3 virus, respiratory syncytial virus and treatment for respiratory disease in Ontario feedlot calves.

A seroepidemiological study of the association between antibody titers to infectious bovine rhinotracheitis, parainfluenza-3, bovine virus diarrhea and bovine respiratory syncytial viruses, and treatment for bovine respiratory disease was conducted. A total of 322 calves from five different groups were bled on arrival, then one month later all cases (cattle treated for bovine respiratory disease) were rebled together with an equal number of controls (cattle not treated for any disease). Titers to these viruses varied significantly from group to group. Based on seroconversion, infectious bovine rhinotracheitis virus was active in 4.4%, bovine virus diarrhea virus in 24%, parainfluenza-3 virus in 69.5% and bovine respiratory syncytial virus in 71.3% of the cattle. Cattle with low titers to infectious bovine rhinotracheitis and/or bovine respiratory syncytial viruses on arrival, were at increased risk of subsequent treatment for bovine respiratory disease. Treated cattle also had significantly greater increases to parainfluenza-3 and/or bovine virus diarrhea viruses than control calves. Treatment rates varied considerably from group to group and were not strongly correlated with weight gain in the postarrival period.     

The association of titers to bovine coronavirus with treatment for bovine respiratory disease and weight gain in feedlot calves.

The association between bovine respiratory disease (BRD) and antibody titers to bovine coronavirus (BCV) was studied in 604 calves (19 different groups in 4 different feedlots from 2 provinces). Almost all calves had antibody titers on arrival in the Alberta feedlot and 82% of the calves had an antibody titer on arrival at the Ontario feedlots; titers in calves in Alberta were almost twice as high as those in calves in Ontario. The incidence of infection, in the first mo after arrival as judged by seroconversion, ranged from 61% to 100%; titer increases were much greater in calves in Ontario feedlots. Titer variables were not significantly related to BRD, except on a within-group basis (group was a confounding variable for BCV-BRD associations). Given control of group effects, calves with an antibody titer on arrival appeared to be protected against BRD for the first 28 d in the feedlot, and the association was reasonably linear over the range of titers. Each titer unit on arrival decreased the risk of BRD by about 0.8x (odds ratio). Titer change was not strongly related to the risk of BRD and the relationship was not linear over the range of titer changes. Titer change was strongly and negatively correlated with titer on arrival, and titer change was not significantly related to BRD in the presence of arrival titers. Arrival titer retained its relationship with BRD in the presence of titer data for other putative pathogens. Each higher unit of titer to BCV on arrival increased the 28-day weight gain (controlling for group, initial weight and the occurrence of BRD) by slightly more than 1 kg. Titer change was associated with decreased weight gain, when initial titer was not in the model. The lack of a linear or multivariable association between BCV titer change and BRD, and weight gain, may indicate that BCV is not a major pathogen; or, its lack of significance may merely be due to its strong correlation with arrival titer. Given the associations found in this study, particularly the interprovincial differences in arrival titers, more and different approaches to studying the possible effects of BCV on BRD are in order.     

A field investigation of the economic impact of respiratory disease in feedlot calves

A trial involving 512 beef calves was conducted in a commercial research feedlot to determine the effect of bovine respiratory disease (BRD) on performance parameters and carcass characteristics. Two hundred and fifty-six calves that were deemed to be “sick” (S) from BRD were allocated to 16 pens and 256 calves that were considered to be “well” (W) were allocated to another 16 pens. The outcome variables that were measured included average daily gain (ADG), daily dry matter intake (DDMI), dry matter intake to gain ratio (DM:G), BRD treatment rate, death loss, carcass traits, and net profit per pen.

The data were partitioned into several time intervals including processing (P) to day −1, day 0 to day 27, day 28 to day 55, day 56 to day 83, day 84 to day 111, day 112 to day 139, day 140 to slaughter, day 0 to slaughter (0-Slaugh), and processing to slaughter (P-Slaugh). However, the most important interval was from processing to slaughter.

For the interval P-Slaugh, there were no significant (p≥0.05) differences between the S and W groups with respect to ADG and DM:G. Also, for the interval 0-Slaugh, the DDMI was similar for both groups. There were no significant (p≥0.05) differences between the S and W groups for carcass weight, average fat, grade fat, rib eye area, marbling score, cutability estimate, or carcass grade distribution.

The BRD treatment rates in the S and W groups were 6.6% and 4.7%, respectively. The mortality rates in the S and W groups were 0.78% and 0.39%, respectively. Also, there were no deaths attributable to BRD in either group.

In the economic model, there was no significant (p≥0.05) difference between the S and W groups with respect to net profit per pen.

We conclude that this trial did not validate the concept that BRD impacts performance parameters, because a sufficient disease challenge was not present. However, this study provides several observations that will enhance the experimental design of future studies that attempt to quantify the total economic impact of BRD.

     

The associations of viral and mycoplasmal antibody titers with respiratory disease and weight gain in feedlot calves

Blood samples from 32 groups of calves (n = 700) were taken on arrival and after 28-35 days at the feedlot. Eleven groups were housed in feedlots in Ontario, and 21 groups in feedlots in Alberta. Serum antibody titers to bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), parainfluenza virus type 3 (PIV-3), infectious bovine rhinotracheitis virus (IBRV), Mycoplasma dispar and M. bovis, plus data on bovine corona virus (BCV) from a previous study were investigated for their association with the risk of bovine respiratory disease (BRD), and with 28-day weight change, both before and after controlling for titers to Pasteurella haemolytica and Haemophilus somnus. Exposure to IBRV and M. bovis was infrequent, and although exposure to PIV-3 was more common, none of these agents had important associations with BRD. Higher titers to BVDV, BRSV, and BCV on arrival were associated with reduced risks of BRD and increased weight gains. However, there was some variation in these relationships and higher arrival titers to BVDV and BRSV in a subset of the calves were associated with increased risks of BRD. Titer increases to BVDV were associated with a higher risk of BRD and lower weight gains. Titer increases to BRSV were not usually associated with the occurrence of BRD, but titer increases to BRSV in a subset of calves that were vaccinated against BRSV, on arrival, were associated with an elevated risk of BRD. Of all the agents studied, BVDV had the most consistent associations with elevated risk of BRD and lower weight gains. Higher BRSV arrival titers were related to lower risk of BRD and higher weight gains; in some instances titer increases to BRSV were associated with higher BRD risk. Higher titers to BCV on arrival were related to reduced risks of BRD. Practical ways of adequately preventing the negative effects of these agents are still needed.     

Association between changes in eating and drinking behaviors and respiratory tract disease in newly arrived calves at a feedlot

OBJECTIVE: To investigate eating and drinking behaviors and their association with bovine respiratory disease complex (BRDC) and to evaluate methods of diagnosing BRDC. ANIMALS: 170 newly arrived calves at a feedlot. PROCEDURE: Eating and drinking behaviors of calves were recorded at a feedlot. Calves with clinical signs of BRDC were removed from their pen and classified retrospectively as sick or not sick on the basis of results of physical and hematologic examinations. Pulmonary lesions of all calves were assessed at slaughter. RESULTS: Calves that were sick had significantly greater frequency and duration of drinking 4 to 5 days after arrival than calves that were not sick. Sick calves had significantly lower frequency and duration of eating and drinking 11 to 27 days after arrival but had significantly greater frequency of eating 28 to 57 days after arrival than calves that were not sick. Calves at slaughter that had a higher percentage of lung tissue with pneumonic lesions had significantly lower frequency and duration of eating 11 to 27 days after arrival but had significantly higher frequency and duration of eating 28 to 57 days after arrival. Agreement for calves being sick and having severe pulmonary lesions at slaughter was adequate. Agreement for calves being removed and having pulmonary lesions at slaughter was low. CONCLUSIONS AND CLINICAL RELEVANCE: Eating and drinking behaviors were associated with signs of BRDC, but there was not an obvious predictive association between signs of BRDC in calves and eating and drinking behaviors. Fair to poor agreement was observed between antemortem and postmortem disease classification.     

The microbial flora of the respiratory tract in feedlot calves: associations between nasopharyngeal and bronchoalveolar lavage cultures.

The upper and lower respiratory tracts of 59 feedlot calves with clinical signs of naturally occurring respiratory disease (cases) and 60 comparison (control) animals were cultured before treatment, using nasopharyngeal swabs (NPS) and bronchoalveolar lavage (BAL). The most prevalent organisms were Pasteurella multocida and Mycoplasma bovis. Isolations of P. multocida from NPS and BAL fluid were found to be significantly associated with morbidity (p less than or equal to 0.05), but the frequency with which other organisms were isolated from the nasopharynx and lungs was similar in cases and controls. There was evidence of moderate agreement between NPS and BAL isolates at the individual calf level using the kappa statistic, (range of kappa values = 0.47-0.61) but the variability of the kappa statistics was large. Therefore, in an individual calf NPS cultures did not accurately predict BAL cultures. The NPS and BAL culture results were quite similar at the group level, however.     

The association of titers to Haemophilus somnus, and other putative pathogens, with the occurrence of bovine respiratory disease and weight gain in feedlot calves.

Serum samples were obtained from 602 calves (from 19 groups in four feedlots: three in Ontario, and one in Alberta) upon arrival at the feedlot and 28 d later. Of these calves, 202 developed bovine respiratory disease (BRD) and 400 did not develop BRD. Based on high antibody titers noted upon arrival, we infer that most calves were exposed to Haemophilus somnus prior to arrival at the feedlot. Within a group, calves with high titers on arrival had a reduced risk of developing BRD later. Most calves did not experience titer increases after arrival; however, calves that had stable or increasing titers had a relatively low risk of contracting BRD. The calves at greatest risk of BRD were those with titers on arrival of less than 6.8 units and subsequent titer decreases of more than 1 unit. The effects of both the titer on arrival and the titer change after arrival were stable when the serologic effects of a number of viruses and Mycoplasma agents were considered. Neither antibody titer on arrival nor titer change was related to weight gain differences among calves. Calves with BRD or calves with lower weight on arrival had decreased weight gains in the first 28-day feeding period. The high titers on arrival may have protected most calves against further infection with H. somnus. However, since the calves that developed BRD had large titer increases to a number of viruses and to Pasteurella haemolytica, while having decreased antibody titers to H. somnus, we infer that the existing antibodies were "used up" in combatting the agents, including H. somnus, which may have "caused" the BRD. Calves which were able to increase their antibody levels to H. somnus tended to have a reduced risk of BRD.     

Bovine adenovirus type-3 infection in feedlot calves

The frequency of bovine adenovirus type-3 (BA3) infection in 84 of 165 light feeder calves and the possible role of BA3 in inducing febrile disease and affecting weight gain performance were studied for 56 days after the calves entered a feedlot. Samples of blood for serotesting were obtained periodically, and samples for virus isolation were collected on days 28 and 56. At the time the calves entered the feedlot, 17.8% (15 of 84) had serum virus-neutralizing antibodies to BA3. During 56 days, 54.8% (46 of 84) seroconverted to BA3. Of these seroconversions, 87% took place during the first 28 days. Bovine adenovirus type-3 was isolated from 2 calves (1 isolate each on days 28 and 56). Pyrexia (greater than or equal to 39.2 C) was observed more often in BA3-infected calves than in noninfected calves. However, there was no significant (P less than 0.05) difference in weight gain between the BA3-infected and noninfected calves.     

The relationship of hematology and serum chemistry parameters to treatment for respiratory disease and weight gain in Ontario feedlot calves.

In the fall of 1983, 322 western calves, in five different groups, were bled on arrival at two Ontario feedlots. Calves receiving treatment for respiratory disease, within 35 days of arrival, were denoted as cases. The hematology and serum chemistry parameters of cases were compared to those of controls. Cases had significantly (p less than 0.05) lower hematocrits, fewer platelets, and more band cells on arrival, than did controls. Cases also had lower serum phosphorous, magnesium, potassium, iron and alkaline phosphatase levels, and increased bilirubin and aspartate aminotransferase levels relative to controls. Based on the results of multivariable logistic regression, hematocrit, platelet numbers, serum phosphorous, iron and aspartate aminotransferase levels were the most significant parameters for the prediction of respiratory disease. Reference values for stressed feedlot calves were created. Most parameters were distributed in an approximately normal manner, however the group to group variation in most parameters was significant.     

A comparison of trimethoprim-sulfadoxine and ceftiofur sodium for the treatment of respiratory disease in feedlot calves

A field trial was performed to compare trimethoprim-sulfadoxine to ceftiofur sodium in the treatment of bovine respiratory disease (BRD) in feedlot calves. Five-hundred-and-fifty-five recently weaned, crossbred beef calves, with naturally occurring cases of BRD, were randomly assigned to either trimethoprim-sulfadoxine or ceftiofur sodium treatment groups. The effectiveness of the antibiotics was assessed by comparing relapse rates, three day treatment response rates, mortality rates, chronicity rates, and wastage rates. There was no statistical difference in the first or second relapse rates between the two groups. For the initial therapy, first relapses, and overall treatment episodes, a significantly greater proportion of the calves treated with ceftiofur sodium responded to three days of therapy than those treated with trimethoprim-sulfadoxine (p < 0.05). This resulted in a 10% reduction in treatment costs for calves in the ceftiofur group. There were significantly lower mortality and wastage rates attributable to BRD in the ceftiofur sodium group than in the trimethoprim-sulfadoxine group (p < 0.05). However, there were no significant differences in overall mortality, overall chronicity, or overall wastage rates between the treatment groups.     

The relationship between total protein in serum, glutaraldehyde coagulation test and disease in feedlot calves

Serum from in all 249 calves were used to correlate the level of total protein (serum-Tp), gamma-globulin and the reaction of glutaraldehyde coagulation test (GCT) to each other. Further, of the 249 calves 219 were bled within two days after arrival to a feedlot and serum-Tp and GCT were related to subsequent diseases. The results revealed a close relationship between the three tests. Of the 219 calves 15% had a negative GCT (hypogammaglobulinemia) and 26% had a serum-Tp below 55 g/l. There was a significantly (p less than 0.001) higher disease frequency, 81%, in the GCT negative calves than in the GCT positive, 35%. Serum-Tp was significantly (p less than 0.001) higher in healthy compared to diseased calves. The mean values were 60.6, 57.2, 55.2 and 53.1 g/l for healthy calves, calves with respiratory disease, enteritis and both respiratory disease and enteritis respectively. Further, calves with a serum-Tp below 55 g/l developed disease earlier after arrival to the feedlot than those above this limit. It was concluded that both serum-Tp and GCT can be used in field investigation to identify calves predisposed to disease.     

A group level analysis of the associations between antibodies to seven putative pathogens and respiratory disease and weight gain in Ontario feedlot calves.

The associations, at the group level, between serological titer to Pasteurella haemolytica surface antigens (Ph), Pasteurella haemolytica cytotoxin (Ph-cytox), infectious bovine rhinotracheitis virus (IBRV), bovine virus diarrhea virus (BVDV), parainfluenza-3 virus (PIV3), respiratory syncytial virus (RSV), Mycoplasma dispar (Md), M. bovis (Mb), and respiratory disease treatment rates, relapse rates, and 28 day weight gains were investigated in 14 groups of calves entering two feedlots during years 1983-1985, in Ontario. Based on least squares regression analyses, seroconversion rates to Mb and BVDV were predictive of increased respiratory disease rates, and seroconversion rates to Ph, Ph-cytox, Md and PIV3 were predictive of decreased weight gains. The R2 for predicting weight gains was much higher than for morbidity rates (0.75 vs 0.47 respectively). Titer data were not predictive of relapse rates. Group level analyses were performed because calves are managed as groups (e.g. pens) in commercial feedlots. Only BVDV seroconversion rates were related to increased risk of respiratory disease at both the individual and group levels of organization. Mycoplasma may be important factors in causing respiratory disease, and their relationship to potentiating the effects of other respiratory pathogens needs further investigation.     

Immunofluorescence in the serological diagnosis of parainfluenza type 3 and respiratory syncytial virus infection in calves

The fluorescent antibody (FA) test is compared with the haemagglutination inhibition (HI) test for parainfluenza virus type 3 (PI-3) and virus neutralisation (VN) test for respiratory syncytial (RS) virus for detection and titration of virus-specific antibodies. In experimentally inoculated calves PI-3 and RS virus FA tests detected seroconversion at the same time as HI and VN tests, however, in serially diluted sera, the FA test was positive to higher dilution. In studies with paired samples from calves from four farms with respiratory problems, the FA test gave similar results to PI-3 HI and RS virus VN tests. Large increases in antibody titre to RS virus detected by FA and VN tests indicated this was the problem on two of the farms. Individual animals showed large rises to PI-3 by FA and HI test on three farms. It is concluded that the FA test provides a rapid and sensitive alternative to the more conventional serological tests for respiratory viruses.     

The frequency, distribution and effects of antibodies, to seven putative respiratory pathogens, on respiratory disease and weight gain in feedlot calves in Ontario.

During 1983-85, 279 calves requiring treatment for bovine respiratory disease and 290 comparison (control) animals from 15 different groups of feedlot calves were bled on arrival and again at 28 days postarrival. Their sera were then analyzed for antibodies to seven putative respiratory pathogens. On arrival, the prevalences of indirect agglutination titers to Pasteurella haemolytica, P. haemolytica cytotoxin, Mycoplasma bovis and M. dispar were greater than 50%, the prevalence of titers to bovine virus diarrhea virus (BVDV) was approximately 40%, and the prevalences of titers to infectious bovine rhinotracheitis virus (IBRV), bovine respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) were all below 25%. Seroconversion during the first month after arrival occurred in more than half the calves to P. haemolytica cytotoxin, PIV3 and RSV. Seroconversion of agglutination titers to P. haemolytica, Mycoplasma and BVDV occurred in about 40% of calves, and seroconversion to IBRV was infrequent (less than 5%). Initial titers were negatively correlated to subsequent titer changes within organism. Initial titers, and titer changes between organisms were essentially independent. Light calves had an increased risk of being selected for treatment for respiratory disease. Seroconversion to P. haemolytica cytotoxin, RSV and BVDV were predictive of respiratory disease cases, explaining approximately 69% of all respiratory disease cases in the feedlots. It was not possible to accurately predict weight gain or relapse from the serological data.     

Epizootiological examination of a respiratory disease associated with mycoplasma infection in horse

The authors examined 585 samples from 92 mares of 2 studs and 346 nasal swabs taken from their foals for the presence of mycoplasmas. The positive rates of mares and foals were 81.5% and 71.7%, respectively, with positivity of samples being variable. Clinical symptoms developed in 2-4 waves and lasted 3-7 days, with intervals of 7-12 days. The disease started in April among foals born in February, at an average age of 88 days. Later on, the average age of the affected foals decreased. There was a correlation between presence of mycoplasmas in nasal cavity and disease of foals.     

Efficacy of parenteral antibiotics for disease prophylaxis in feedlot calves

Trimethoprim-sulfadoxine (TMPSDX) and two formulations of oxytetracycline (OTC) were examined for their prophylactic efficacy in feedlot calves when given by intramuscular injection on arrival at a large commercial feedlot. The study included 2,112 high-risk feeder calves that developed disease early in the feeding period. Both formulations of OTC reduced bovine respiratory disease morbidity during the first two weeks on feed and for the entire feeding period by 15-19% (p<0.05), and they also reduced all fatal fibrinous pneumonia by 67% and 84% (p<0.05). All three drugs significantly reduced all fatal disease in animals first treated during the second week on feed, but not for the overall feeding period. Oxytetracycline with 2-pyrrolidone reduced the incidence of all fatal disease by 44% (p<0.05) during the entire feeding period. The case fatality risk for calves first treated during the second week on feed was lower (p<0.05) in the TMPSDX group and in the OTC with polyvinyl-pyrrolidone group.