A total of 838 outbreaks of fatal Haemophilus somnus infections in herds of cattle were diagnosed at provincial veterinary laboratories in Manitoba, Saskatchewan, Alberta and British Columbia during the period 1969-1978. The index cases from these outbreaks included 759 cases of thromboembolic meningoencephalitis, 78 cases of fibrinous pneumonia with pleuritis and one case of H. somnus abortion. The epizootics were subdivided on the basis of province, class and age of cattle and seasonal occurrence. Most outbreaks occurred in a feedlot-type of operation, approximately four weeks after arrival of the cattle. There was often a history of respiratory disease prior to an outbreak and in some cases thromboembolic meningoencephalitis had occurred in the herd the preceding year. The average morbidity-mortality ratio was 2.7/1. The average economic loss per herd was $3 190 based on an average of 15 sick animals and five deaths per affected herd.
The molecular diversity of rumen methanogens in feedlot cattle and the composition of the methanogen populations in these animals from two geographic locations were investigated using 16S rRNA gene libraries prepared from pooled PCR products from 10 animals in Ontario (127 clones) and 10 animals from Prince Edward Island (114 clones). A total of 241 clones were examined, with Methanobrevibacter ruminantium accounting for more than one-third (85 clones) of the clones identified. From these 241 clones, 23 different 16S rRNA phylotypes were identified. Feedlot cattle from Ontario, which were fed a corn-based diet, revealed 11 phylotypes (38 clones) not found in feedlot cattle from Prince Edward Island, whereas the Prince Edward Island cattle, which were fed potato by-products as a finishing diet, had 7 phylotypes (42 clones) not found in cattle from Ontario. Five sequences, representing the remaining 161 clones (67% of the clones), were common in both herds. Of the 23 different sequences, 10 sequences (136 clones) were 89.8 to 100% similar to those from cultivated methanogens belonging to the orders Methanobacteriales, Methanomicrobiales, and Methanosarcinales, and the remaining 13 sequences (105 clones) were 74.1 to 75.8% similar to those from Thermoplasma volcanium and Thermoplasma acidophilum. Overall, nine possible new species were identified from the two clone libraries, including two new species belonging to the order Methanobacteriales and a new genus/species within the order Methanosarcinales. From the present survey, it is difficult to conclude whether the geographical isolation between these two herds or differences between the two finishing diets directly influenced community structure in the rumen. Further studies are warranted to properly assess the differences between these two finishing diets.
The results of the second year of the project confirmed most of the major findings from the initial year. Feeding cornsilage, particularly as the major roughage in the first month after arrival was associated with excess mortality. Mixing of cattle from different sources and vaccinating against respiratory disease appeared to be the most important additional factors that increased mortality rates. Delaying vaccination at least two days postarrival may have prevented the negative effects of vaccination but only in calves fed cornsilage. Morbidity rates were highly variable among farms but were positively correlated with mortality rates and treatment costs. The occurrence of infectious thromboembolic meningoencephalitis appeared to share some of the same risk factors as mortality; whereas, urolithiasis did not. Water deprivation may be a risk factor in the occurrence of urolithiasis. Fibrinous pneumonia was again the most frequent cause of death. Relative to year one, infectious thromboembolic meningoencephalitis increased in frequency and only one death was attributed to bovine virus diarrhea.
Nonimmune binding of immunoglobulin to whole bacteria was quantitated for North American isolates of Haemophilus somnus recovered from cattle with pneumonia, reproductive failure (abortion), or thromboembolic meningoencephalitis or from the vagina or prepuce of carrier cattle. Quantitative binding activity covered a wide range, with most pathogenic and carrier isolates demonstrating significant immunoglobulin-Fc binding. Isolates for which Fc binding was not detectable were recovered only from the prepuces of asymptomatic bulls. Expression of Fc-binding activity correlated with the presence of the 41,000-molecular-weight protein (41K protein) and 270K protein. Isolates that lacked Fc-binding activity did not possess 41K or 270K protein. A 33K protein was detected in isolates that lacked Fc-binding activity but not in isolates that bound Fc.
A 78-kilodalton (kDa) outer membrane protein (OMP) of Haemophilus somnus was one of the two antigens most consistently and most intensely immunoreactive in Western immunoblots of whole cells of H. somnus reacted with convalescent-phase serum obtained from cattle with experimental H. somnus pneumonia. This antigen was isolated by gel filtration chromatography of sodium dodecyl sulfate-solubilized OMP. Reactions of Western blots with bovine monospecific antiserum prepared against the 78-kDa antigen indicated that this 78-kDa OMP was present in each of 22 isolates of H. somnus obtained from cattle with pneumonia, thromboembolic meningoencephalitis, and abortion as well as from vaginal or preputial carriers. The 78-kDa OMP was also present in each isolate obtained weekly throughout the course of experimental H. somnus pneumonia in a calf. Monospecific antiserum to the 78-kDa OMP also reacted with proteins from closely related bacterial species in the family Pasteurellaceae but not with bacteria of 13 other genera. The 78-kDa OMP of H. somnus is of interest because it is surface accessible, highly conserved, immunogenic, cross-reactive with other members of the family Pasteurellaceae, and reactive with convalescent-phase serum which is passively protective against H. somnus pneumonia.
An outbreak of cysticercosis (infestation with the larvae of Taenia saginata) occurred in feedlot cattle in Ontario in 1986. Two hundred and thirty-three of 271 steers were confirmed histologically to be positive for cysticerci. Nineteen (8.2%) animals had viable cysticerci, 87 (37.3%) had degenerated cysticerci, 77 (33.0%) had mineralized cysticerci, and 50 (21.5%) steers had lymphoid granulomas consistent with cysticercosis. Three viable cysticerci were partly evaginated and one degenerate cysticercus was fully evaginated.
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.
Three years of data on factors associated with death losses and health costs in Ontario feedlot calves were analyzed. The results support the previously reported findings; however, significant differences in the third year (1980-81) of the study were noted. Calf groups that were "mixed" after arrival in the feedlot or had a larger than average number of calves (means = 142) had increased death losses and health costs. Calf groups whose ration was changed from dry hay to hay silage or corn silage as the major component of the ration during the first month after arrival had higher death losses and health costs. Feeding grain (barley/oats/corn) prior to, or concurrent with, the change to silage appeared to decrease the harmful effects. Cattle groups vaccinated against respiratory disease within two weeks of arrival experienced increased death losses and health costs. These effects were ameliorated by delaying vaccination in groups switched to silage; however, no benefits from delaying vaccination were noted in dry hay fed groups. Prophylactic antimicrobials in the water supply during the first week after arrival appeared particularly deleterious to the health of calf groups. The effects of prophylactic antimicrobials in the starter ration were unclear. During 1980-81, there was a marked decrease in the relative importance of fibrinous pneumonia as a cause of death and the feeding of silage was not significantly associated with mortality. Both these events may have arisen from the drastic decrease in the percentage of groups fed silage by two weeks postarrival (from 32% in previous years to 7% in 1980-81).
The design and results of a mail survey of a simple random sample of southwestern Ontario feedlot owners are presented. The survey provided general data about management of feedlot calves and the association between a number of factors and disease and/or death rates. The number of calves purchased was related positively, in a linear manner, to mortality and morbidity rates. Increased levels of morbidity and mortality were noted when the ration was changed to corn silage from dry-hay within the first month after arrival. However, it was not clear whether the ration changes preceded or followed increased rates of morbidity and mortality. Prophylactic levels of antimicrobials in the water supply were associated with increased death losses. Shipping cattle by truck, rather than train, was associated with decreased rates of disease. Processing factors, including using vaccines against respiratory disease, were not associated significantly with mortality or morbidity. It was concluded that reducing the number of calves, to approximately 100 per group, not changing the ration to silage within the first month and not using antibiotics in the water supply on arrival could significantly reduce disease and death losses.
Studies were performed to establish the prevalence and importance of tail tip necrosis in the southern Ontario beef feedlot industry and to characterize the gross appearance and histopathology of the condition. In a mail survey, 96% of 71 feedlots with slatted floors, but only 5% of 184 feedlots with solid floors, reported a problem with tail tip necrosis from 1982-1986. Treatments reported included antibiotics, amputation of the tail (therapeutic or preventive), and slaughter. Lameness was associated with tail tip necrosis.
A scoring system for severity of necrosis was developed. Repeated inspections revealed that mild lesions were unlikely to progress to more severe stages. Histological alterations such as perivascular edema and hemorrhage, dermal scarring, follicular atrophy, and paucity of leukocytes were compatible with cutaneous ischemia.
Of 441 tails inspected at slaughter plants, 34.5% were affected, with 3.4% involving skin lacerations and infection, and 4.3% amputated before slaughter.
Q or “query” fever is a zoonosis caused by the organism Coxiella burnetii. Cattle, sheep and goats are the most common reservoirs of this organism. The placenta of infected animals contains high numbers (up to 109/g) of C. burnetii. Aerosols occur at the time of parturition and man becomes infected following inhalation of the microorganism. The spectrum of illness in man is wide and consists of acute and chronic forms. Acute Q fever is most often a self-limited flu-like illness but may include pneumonia, hepatitis, or meningoencephalitis. Chronic Q fever almost always means endocarditis and rarely osteomyelitis. Chronic Q fever is not known to occur in animals other than man. An increased abortion and stillbirth rate are seen in infected domestic ungulates.
Four provinces (Nova Scotia, New Brunswick, Ontario and Alberta) reported cases of Q fever in 1989.
A vaccine for Q fever has recently been licensed in Australia.
Kidneys from 117 cattle from 110 Ontario farms were examined at slaughter for leptospires. Leptospira hardjo (hardjo-bovis A) was isolated from 11 kidneys and L. kennewicki from one. The isolations were all made (12/89, 13.5%) from beef cattle from feedlots, no isolates being obtained from dairy or beef cattle from extensive farms (0/28). Isolations were only made from cattle with antibody titers (greater than or equal to 20) against the serovars recovered. Isolation was more sensitive than immunofluorescence in identifying leptospira, particularly in animals with low antibody titers against L. hardjo. Leptospira were isolated from two kidneys with multiple gross lesions of focal nephritis, but there was no correlation between the presence of scanty kidney lesions and isolations of leptospira. Leptospira hardjo infection appears to be common in Ontario feedlot cattle.
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.
Epidemic curves, odds ratios and chisquare were used to investigate an epidemic of respiratory disease in a pen of feedlot cattle. The cattle were divided into four groups by an eartag number received at processing. Data for each group were collected from feedlot records describing purchase, transportation and processing histories, daily feeding methods, daily pen movements, daily diagnoses, treatment and mortality rates. These data were used to describe the effects of market origin and feeding management on the levels and distribution of respiratory disease.
The three groups of cattle purchased from auction markets and started on high levels of grain in their rations were determined to be 6.3 times (P<0.0005) more likely to be treated for any disease, 4.9 times (P<0.0005) more likely to be treated for respiratory disease, 12.7 times (P<0.0025) more likely to die, and 6.7 times (P<0.0471) more likely to die with respiratory disease than the group made up primarily of farm-assembled heifers and started on a 10% grain ration with time for adjustment to grain.
Bovine respiratory disease; feedlot management; cattle stress; feedbunk management; feedlot ration management; feedlot market origins; mixing cattle in feedlots
The prevalence of Escherichia coli O157 associated with feedlot cattle in Saskatchewan was determined in a 10-month longitudinal study (3 feedlots) and a point prevalence study (20 feedlots). The prevalence of E. coli O157 at the three different sites in the horizontal study varied from 2.5 to 45%. The point prevalence of E. coli O157 among Saskatchewan cattle from 20 different feedlots ranged from 0% to a high of 57%. A statistically significant (P = 0.003) positive correlation was determined to exist between the density of cattle and the E. coli O157 prevalence rate. A significant correlation (P = 0.006) was also found between the E. coli O157 percent prevalence and the number of cattle housed/capacity ratio. All 194 E. coli O157 isolates obtained were highly virulent, and random amplified polymorphic DNA PCR analysis revealed that the isolates grouped into 39 different E. coli O157 subtypes, most of which were indigenous to specific feedlots. Two of the most predominant subtypes were detected in 11 different feedlots and formed distinct clusters in two geographic regions in the province. Antimicrobial susceptibility testing of the E. coli O157 isolates revealed that 10 were multidrug resistant and that 73 and 5 were resistant to sulfisoxazole and tetracycline, respectively.
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.
The purpose of this study was to describe the prevalence and longitudinal distribution of Escherichia coli O157 in feedlot cattle and the feedlot environment. Pen floors, water tanks, other cattle in the feedlot, feed, and bird feces were sampled for 2 weeks prior to entry of the study cattle. Twelve pens of study cattle were sampled twice weekly. At each sample time cattle feces, water from tanks in each pen, bunk feed, feed components, bird feces, and houseflies were collected. Bunk feed samples were collected before and after cattle had access to the feed. Overall, 28% of cattle fecal samples, 3.9% of bird fecal samples, 25% of water samples, 3.4% of housefly samples, 1.25% of bunk feed before calf access, and 3.25% of bunk feed samples after cattle had access to the feed were positive for E. coli O157. Genetic analysis of E. coli O157 isolates was done using pulsed-field gel electrophoresis (PFGE). PFGE types identified in sampling of the feedlot prior to calf entry were different than the majority of types identified following calf entry. A single strain type predominated in the samples collected after entry of the cattle. It was first identified 5 days after entry of the first pen of cattle and was subsequently identified in all pens. Data support that the incoming cattle introduced a new strain that became the predominant strain in the feedlot.
The serum susceptibility of 64 isolates of Haemophilus somnus from cattle was determined in a bactericidal assay with undiluted fresh or inactivated bovine serum with serial dilutions of bacterial suspension in RPMI 1640 medium. A total of 27 strains isolated from cattle with clinical disease (4 with thromboembolic meningoencephalitis, 13 with pneumonia, and 10 with reproductive failure) were compared with 35 strains from asymptomatic carriers (11 from the vagina and 24 from the prepuce). Essentially, all clinical isolates were serum resistant, whereas approximately 25% of preputial isolates were serum susceptible, as judged after 1 h of incubation in serum; a majority of vaginal isolates showed delayed serum susceptibility. Lysozyme played no role in serum killing, and the alternative complement pathway played only a minor role. Iron saturation, however, appeared to impart greater serum resistance to serum-susceptible strains from the vagina and prepuce. Perhaps the serum-susceptible strains from carriers would be useful vaccine candidates, but resistant strains from carriers may be pathogenic.
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.
Field trial; respiratory disease; vaccine; bacterin; preimmunization
Giardia duodenalis is a ubiquitous protozoan parasite that has emerged as a significant opportunistic human pathogen. G. duodenalis may have a deleterious effect on animal growth and performance, therefore its potential as a production limiting organism should not be discounted. We therefore undertook this study to determine management and environmental factors in feedlots that influence the prevalence and environmental load of G. duodenalis cysts in fecal material deposited by feedlot cattle in the central and western United States.
Twenty two feedlots from 7 states were included in the study, and up to 240 fecal samples were collected from pen floors of up to 6 pens per feedlot. Giardia duodenalis cysts were identified and counted using direct immunofluorescent microscopy. The estimated overall point prevalence of G. duodenalis was 19.1%, representing feedlots from a wide range of climates and management systems. Pen-level prevalence varied from 0 to 63.3%, with pen-level shedding estimates ranging from 0 to 261,000 cysts/g feces. Higher environmental temperatures, increased animal density, and increased time in the feedlot were associated with a lower prevalence of G. duodenalis. Removing manure before placing a new group of cattle in a pen was associated with a decreased prevalence of G. duodenalis in fecal pats. Using coccidiostats as a feed additive was associated with a higher prevalence of Giardia.
Management practices could be employed that would limit the probability that feedlot cattle shed G. duodenalis in their feces and therefore potentially limit contamination of their environment.
An outbreak of infectious rhinotracheitis affecting four herds of dairy cattle was observed in the Province of Quebec, the general characteristics of which are the same as those reported in the infection of feedlot cattle.
However, a 25% average decrease in the milk production of affected herds was noticed during the present infection, thus stressing a particular economic aspect. The nature of the viruses isolated during this outbreak and those described previously in North America is identical.
A total of 1,408 cattle held in eight commercial feedlot pens were used to examine the quantity and diversity of microorganisms in cattle feedlot air. The effect of two feeding patterns on the generation of airborne dust and the total numbers of microorganisms was also examined (four feedlot pens/treatment). Microbial samples were collected, and dust particles that were 2.5 μm or less in diameter were measured with a Dustrak monitor during the evening dust peak for 4 days at sites both upwind and downwind of the feedlot pens. An Andersen biological cascade sampler was employed with different medium and incubation combinations for the capture and identification of bacteria and fungi. The results showed that when bacteria were considered, only nonpathogenic gram-positive organisms were recovered. However, gram-negative bacteria may have been present in a viable but nonculturable state. Fungi were recovered in smaller numbers than bacteria, and none of the fungi were pathogenic. The Dustrak results showed that one feeding pattern resulted in cattle behavior that generated levels of downwind dust lower (P = 0.04) than the levels generated by the behavior resulting from the other feeding pattern. However, the Andersen sampler results showed that there were no differences between feeding patterns with regard to the total number or diversity of microorganisms. The disparity may have been due to the different operating principles of the two systems. The overall numbers of microorganisms recovered were lower than those reported in studies of intensively housed farm animals in which similar recovery techniques were used.
A feedlot trial was conducted to assess the efficacy of an Escherichia coli O157:H7 vaccine in reducing fecal shedding of E. coli O157:H7 in 218 pens of feedlot cattle in 9 feedlots in Alberta and Saskatchewan. Pens of cattle were vaccinated once at arrival processing and again at reimplanting with either the E. coli O157:H7 vaccine or a placebo. The E. coli O157:H7 vaccine included 50 μg of type III secreted proteins. Fecal samples were collected from 30 fresh manure patties within each feedlot pen at arrival processing, revaccination at reimplanting, and within 2 wk of slaughter.
The mean pen prevalence of E. coli O157:H7 in feces was 5.0%; ranging in pens from 0% to 90%, and varying signif icantly (P < 0.001) among feedlots. There was no signif icant association (P > 0.20) between vaccination and pen prevalence of fecal E. coli O157:H7 following initial vaccination, at reimplanting, or prior to slaughter.
The pneumonic lungs of 42 cattle from 26 feedlots were examined for the presence of mycoplasma, pathogenic bacteria and viruses. Four animals representative of two lots failed to yield mycoplasma. One of these yielded the virus of infectious bovine rhinotracheitis and Pasteurella hemolytica, the other yielded only P. P. multocida. Nine animals in eight lots yielded Mycoplasma sp.: five of these were M. bovirhinis, two were M. arginini and two were untypable. All of these animals yielded one or more of P. hemolytica, P. multiocida, infectious bovine rhinotracheitis virus or bovine virus diarrhea virus. Twenty-five of 29 animals in 16 lots yieled M. agalactiae subsp. bovis from lung tissues. The same organism was recovered from the arthritic joints of 12 of these animals. Eight of the 25 animals yielded no other pathogen and all of these had not received any treatment. Nine of the 25 M. agalactiae subsp. bovis positive animals also yielded one or more of P. hemolytica, P. multocida, Corynebacterium pyogenes or infectious bovine rhinotracheitis virus. Bacteriological and virological studies were not completed for the remaining eight of the 25 positive animals. In five lots of cattle which had not received medication for pneumonia and for arthritis only M. agalactiae subsp. bovis was recovered. Twenty-five grossly normal lungs obtained from normal cattle at the time of slaughter were cultured and all were negative. The possible role of M. agalactiae subsp. bovis in pneumonia and arthritis was discussed.
A retrospective study of the antibody response to Pasteurella haemolytica was conducted by using sera from 368 feedlot cattle divided among five experiments. In three experiments, live vaccines or a bacterin were administered to some of the cattle and others were left as nonvaccinated controls. In two experiments, cattle were not vaccinated. Clinical signs of disease with subsequent recovery developed in 48.0% of the cattle, and 10.3% of the cattle died. Vaccination had no apparent effect on morbidity or mortality. At the time of purchase, 78% of the cattle had low antibody titers (less than 25) as measured by a quantitative fluorometric immunoassay. In most groups of cattle (both vaccinated and nonvaccinated), there was a significant rise in mean antibody titers between the time of purchase and days 28 to 32 in the feedlot. The antibody titers at the time of shipment and health status of cattle. The antibody ratios were significantly greater for cattle that became sick and then recovered compared with those of cattle that remained healthy. Although significance could not be established, antibody titers at the time of shipment were higher for cattle that remained healthy compared with cattle that became sick and then recovered.