Tenderness of beef round muscles containing injection site lesions or bruises

The effect of injection site lesions on shear force was studied in three experiments using beef calves injected at 2 to 6 mo with common vaccines and antimicrobials used in Canada. Lesions produced by clostridial bacterins (Blacklegol® 8, Covexin®-8, Ultrabac® 8), antimicrobials (Nuflor®, Trivetrin™), or a four-way respiratory vaccine (Bovishield™ 4) increased (P = 0.05) shear force values at the site of the lesion and at 2.5 cm from the lesion. The proportion of unacceptably tough meat cores (shear force > 4.6 kg) varied among injectables independent of lesion size. The proportion of unacceptably tough samples was significantly increased up to 7.5 and 12.5 cm from the lesion center for Trivetrin™ and Nuflor®, respectively, but only at 0 and 2.5 cm from the lesion center for the bacterins and Bovishield™ 4. Mean lesion volume varied from 8.6 ± 0.8 cm3 for Bovishield™ 4 to 90.2 ± 6.4 cm3 for one of the clostridial bacterins. The present results suggest that smaller lesions, which may not be identified during meat processing, may have a greater impact on meat tenderness and variability than larger lesions that are removed during processing. Antemortem bruises in two muscles of the round did not appear to affect shear force. Key words: Cattle, beef, tenderness, vaccine, antibiotic, lesion, bruise

Environmental sources and transmission of Escherichia coli O157 in feedlot cattle

A study was conducted in 2 feedlots in southern Alberta to identify environmental sources and management factors associated with the prevalence and transmission of Escherichia coli O157:H7. Escherichia coli O157:H7 was isolated in preslaughter pens of cattle from feces (0.8%), feedbunks (1.7%), water troughs (12%), and incoming water supplies (4.5%), but not from fresh total mixed rations. Fresh total mixed rations did not support the growth of E. coli O157:H7 and E. coli from bovine feces following experimental inoculation. Within a feedlot, the feces, water troughs, and feedbunks shared a few indistinguishable subtypes of E. coli O157:H7. A few subtypes were repeatedly isolated in the same feedlot, and the 2 feedlots shared a few indistinguishable subtypes. The prevalence of E. coli O157:H7 in water troughs of preslaughter cattle in 1 feedlot was associated with season, maximum climatic temperatures the week before sampling; total precipitation the week before sampling, and coliform and E. coli counts in the water trough.

Identification of a mutant bovine herpesvirus-1 (BHV-1) in post-arrival outbreaks of IBR in feedlot calves and protection with conventional vaccination

Outbreaks of infectious bovine rhinotracheitis (IBR) have recently been observed in vaccinated feedlot calves in Alberta a few months post-arrival. To investigate the cause of these outbreaks, lung and tracheal tissues were collected from calves that died of IBR during a post-arrival outbreak of disease. Bovine herpesvirus-1 (BHV-1), the causative agent of IBR, was isolated from 6 out of 15 tissues. Of these 6 isolates, 5 failed to react with a monoclonal antibody specific for one of the epitopes on glycoprotein D, one of the most important antigens of BHV-1. The ability of one of these mutant BHV-1 isolates to cause disease in calves vaccinated with a modified-live IBR vaccine was assessed in an experimental challenge study. After one vaccination, the majority of the calves developed humoral and cellular immune responses. Secondary vaccination resulted in a substantially enhanced level of immunity in all animals. Three months after the second vaccination, calves were either challenged with one of the mutant isolates or with a conventional challenge strain of BHV-1. Regardless of the type of virus used for challenge, vaccinated calves experienced significantly (P < 0.05) less weight loss and temperature rises, had lower nasal scores, and shed less virus than non-vaccinated animals. The only statistically significant (P < 0.05) difference between the 2 challenge viruses was the amount of virus shed, which was higher in non-vaccinated calves challenged with the mutant virus than in those challenged with the conventional virus. These data show that calves vaccinated with a modified-live IBR vaccine are protected from challenge with either the mutant or the conventional virus.

Canadian beef quality audit 1998-99

The second beef quality audit was conducted in Canada in 1998-99 to determine the prevalence of quality defects in slaughtered cattle and to monitor changes since the first audit in 1995. Approximately 0.6% of the number of cattle processed annually in Canada were evaluated. Brands were observed on 49% and tag was observed on 43% of the hides. Both brands and tag had increased from 1995. Seventy percent of the cattle were polled and 5% had full horns; thus, the number of horned cattle had decreased from 1995. Bruises were found on 54% of the carcasses, which was a decrease from 78% in 1995. Sixty-eight percent of the bruises were minor, 28% major, and 4% critical in severity. The distribution of bruises on the carcass was 17% on the chuck, 36% on the rib, 30% on the loin, and 16% on the round. Grubs were observed on 0.008% of the carcasses, and surface injection site lesions were observed on 0.2% of the whole carcasses, a decrease from the 1.3% seen in 1995. Seventy-two percent of the livers were passed for human food and 14% for pet food; 14% were condemned. Approximately 64% of the liver losses were due to abscesses. Five percent of the heads and tongues and 0.3% of the whole carcasses were condemned. The hot carcass weight was highly variable in all cattle, averaging 353 kg (s = 43). The average ribeye area was 90 cm2 (s = 13). Both hot carcass weight and ribeye area had increased from 1995. The average grade fat was 9 mm (s = 5), ranging from 0 mm to 48 mm. Lean meat yield averaged 58.8% (s = 4.6). One percent of the carcasses were devoid of marbling, 17% were Canada A, 49% were Canada AA, 32% were Canada AAA, and 1% were Canada Prime, which was an increase in marbling from 1995. Dark cutters were found in 1% of all carcasses; 1% of steers, 0.5% of heifers, 3% of cows, and 14% of bulls. Three percent of the carcasses were underfinished and 13% were overfinished. The number of overfinished carcasses had increased from 1995. Stages, steers with bullish traits, were infrequently observed in 0.5% of the steers, and 0.2% of the steers and 0.3% of the heifers had poor conformation. Yellow fat was not observed in any steers or heifers, but it was found on 65% of the cow carcasses. Only 0.6% of the heifers had an aged carcass, based on skeletal maturity. Based on August 1998 to July 1999 prices, it was estimated that the Canadian beef industry lost $82.62 per head processed, or $274 million annually, from quality nonconformities, which was an increase from 1995. Additional improvements in management, feeding, handling, genetics, marketing, and grading are needed in the beef industry to reduce quality defects.

The effect of animal health products on the formation of injection site lesions in subprimals of experimentally injected beef calves

Two hundred and twenty beef calves were used in an experimental study to determine the occurrence of injection site lesions at slaughter (15 to 18 months of age) following subcutaneous and intramuscular injection of various products into the top hip (top butt), thigh (round), and neck or rib of calves at birth, branding, or weaning. Products tested were: 2 different preparations of selenium; a 2-way, a 7-way, and an 8-way clostridial bacterin; 2 combination 7-way clostridial and Haemophilus somnus bacterins; 2 H. somnus bacterins; 2 different 4-way modified-live viral respiratory vaccines; a 4-way killed viral and H. somnus vaccine; and penicillin, florfenicol, ceftiofur, trimethoprim-sulfa, and tilmicosin. The occurrence of lesions, number of steaks affected with lesions, the trim weight of lesions, the histological class of lesions, and the estimated economic losses are described. Generally, products administered subcutaneously in the neck produced minimal tissue damage and economic losses.

Monitoring injection site lesions in Canadian yearling cattle and cull cows and bulls: Spring 1998

Injection site lesions were found in 15% top butts, 22% blades, 6% eyes of rounds, 0.4% inside rounds, and 8% outside rounds from yearling cattle, estimated to cost $7.15/head processed ($15 million annually). In cull cows and bulls, lesions were found in 33% outside rounds, estimated to cost $3.56/head processed ($2.3 million annually).

The effect of administering long-acting oxytetracycline and tilmicosin either by dart gun or by hand on injection site lesions and drug residues in beef cattle

Forty yearling cattle were injected intramuscularly with long-acting oxytetracycline and subcutaneously with tilmicosin by dart gun or by hand in a chute 28 days prior to slaughter. The drugs caused injection site lesions and antibiotic residues in the neck and thigh that varied by technique, dose, and site.

The prevalence of verotoxins, Escherichia coli O157:H7, and Salmonella in the feces and rumen of cattle at processing

Fecal samples collected from cattle at processing during a 1-year period were tested for verotoxins (VT1, VT2), Escherichia coli O157:H7, and Salmonella. Verotoxins were detected in 42.6% (95% CI, 39.8% to 45.4%), E. coli O157:H7 in 7.5% (95% CI, 6.1% to 9.1%), and Salmonella in 0.08% (95% CI, 0.004% to 0.5%) of the fecal samples. In yearling cattle, the median within-lot prevalence (percentage of positive samples within a lot) was 40% (range, 0% to 100%) for verotoxins and 0% for E. coli O157:H7 (range, 0% to 100%) and Salmonella (range, 0% to 17%). One or more fecal samples were positive for verotoxins in 80.4% (95% CI, 72.8% to 86.4%) of the lots of yearling cattle, whereas E. coli O157:H7 were detected in 33.6% (95% CI, 26.0% to 42.0%) of the lots. In cull cows, the median within-lot prevalence was 50% (range, 0% to 100%) for verotoxins and 0% (range, 0% to 100%) for E. coli O157:H7 and Salmonella (range, 0% to 0%). Verotoxins were detected in one or more fecal samples from 78.0% (95% CI, 70.4% to 84.2%) of the lots of cull cows, whereas E. coli O157:H7 were detected in only 6.0% (95% CI, 3.0% to 11.4%) of the lots of cull cows. The prevalence of verotoxins in fecal samples was lower in yearling cattle than in cull cows, whereas the prevalence of E. coli O157:H7 in fecal samples was higher in yearling cattle than in cull cows. The prevalence of E. coli O157:H7 in fecal samples was highest in the summer months. Rumen fill, body condition score, sex, type of cattle (dairy, beef), and distance travelled to the plant were not associated with the fecal prevalence of verotoxins or E. coli O157:H7. The prevalence of verotoxins in fecal samples of cull cows was associated with the source of the cattle. It was highest in cows from the auction market (52%) and farm/ranch (47%) and lowest in cows from the feedlot (31%). In rumen samples, the prevalence of verotoxins was 6.4% (95% CI, 4.2% to 9.4%), and it was 0.8% (95% CI, 0.2% to 2.3%) for E. coli O157:H7, and 0.3% (95% CI, 0.007% to 1.5%) for Salmonella.

The effect of vaccines and antimicrobials on the formation of injection site lesions in subprimals of experimentally injected beef calves

Two hundred and thirty-nine beef calves were used to determine the occurrence of injection site lesions at slaughter (16 to 17 mo of age) following the use of 3 different 8-way clostridial bacterins, a 4-way viral respiratory vaccine, various long-acting oxytetracycline preparations, florfenicol, ceftiofur, and trimethoprim-sulfa when injected in the top hip (top butt), thigh (round), or neck (blade) of calves at 2 to 3 or 5 to 7 mo of age. The occurrence of lesions varied by product, route of administration, and location of injection. The number of steaks affected with lesions, the trim weight of lesions, the histological class of lesions, and the economic losses from trim are described.

Experimental inoculation of heifers with bovine adenovirus type 3

Nine 2-year-old heifers having BAd3-neutralizing antibody titers between 1:120 and 1:1080 were individually exposed intranasally to an aerosol of 10(8) pfu of wild type (wt) bovine adenovirus type 3 (BAd3). Four animals were kept as non-inoculated controls. The heifers were examined daily for rectal temperature, weight gain/loss, nasal and ocular discharges, and other clinical signs for 10 d post-inoculation. None of the animals showed any sign of clinical disease. Virus excretion was observed in one animal only on Day 3 post-inoculation. All BAd3-inoculated heifers demonstrated a significant (P < 0.005, paired t-test) rise in BAd3-specific serum IgG, IgG1, or IgG2 ELISA titers and virus-neutralizing antibody titers compared to the titers before inoculation. All virus-inoculated animals demonstrated increased levels of BAd3-specific IgA ELISA titers in nasal secretions. These results suggest that in the presence of circulating BAd3-neutralizing antibodies, intranasal inoculation of cattle with wt BAd3 would result in inapparent infection.

Injection site surveys in Canadian yearling cattle and cull cows and bulls: fall 1997

In subprimals from yearling cattle, lesions were found in 16% top butts, 23% blades, 6% eye of rounds, 3% inside rounds, and 8% outside rounds, costing $ 9.58/head processed ($21 million annually). In cull cows and bulls, lesions were found in 35% outside rounds, costing $6.34/head processed ($4.1 million annually).

Injection site survey in Canadian-fed cattle: spring 1997

A 2nd injection site survey was conducted during the spring of 1997 in Canadian-fed beef. The prevalence of lesions was 13.3% in top butts, 23.1% in blades, 9.1% in eye of rounds, 7.5% in outside rounds, and 1.4% in inside rounds. Losses were $8.05/head processed or $17 million annually.

A survey of injection site lesions in fed cattle in Canada

During November 1996 to January 1997, a survey was conducted at 5 Canadian purveyors to measure the prevalence of injection site lesions in the top butt, boneless blade, outside round, inside round, and eye of the round. As trimmers were cutting these subprimals into steaks, technicians monitored each steak for grossly obvious scars. These scars were trimmed, weighed, and scored as either a "clear scar," "woody callus," or "cyst." All scars were subsequently examined histologically and classified as a "clear scar," "woody callus," "scar with nodules," "mineralized scar," or "cyst." Pieces were observed for broken needles while being processed and none were found. The estimated prevalence of injection site lesions was 18.8% (95% CI, 16.4% to 21.2%) in top butts, 22.2% (95% CI, 18.8% to 25.7%) in boneless blades, 4.9% (95% CI, 3.6% to 6.3%) in the eye of round, 1.8% (95% CI, 1.1% to 2.9%) in the inside round, and 7.6% (95% CI, 5.6% to 9.8%) in the outside round. Some top butts originated from American fed cattle; the estimated prevalence of lesions was 9.0% (95% CI, 5.9% to 12.9%) in American top butts and 22.3% (95% CI, 19.4% to 25.3%) in Canadian top butts. The median weight of the lesions varied among subprimals and ranged from 64 g to 117 g. Histologically, 13% of the scars were clear scars, 47% were woody calluses, 5% were mineralized scars, 34% were scars with nodules, 0.2% were cysts, and 0.9% were normal fat infiltrations. An economic analysis estimated an average loss of $8.95 per fed animal processed or $19 million dollars annually to the Canadian beef industry from injection scars.

Canadian beef quality audit

A study was conducted in 4 Canadian processing plants in 1995-96 to determine the prevalence of quality defects in Canadian cattle. One percent of the annual number of cattle processed in Canada were evaluated on the processing floor and 0.1% were graded in the cooler. Brands were observed on 37% and multiple brands on 6% of the cattle. Forty percent of the cattle had horns, 20% of which were scurs, 33% were stubs, 10% were tipped, and 37% were full length. Tag (mud and manure on the hide) was observed on 34% of the cattle. Bruises were found on 78% of the carcasses, 81% of which were minor in severity. Fifteen percent of the bruises were located on the round, 29% on the loin, 40% on the rib, 16% on the chuck, and 0.02% on the brisket. Grubs were observed in 0.02% of the steers, and injection sites were observed in 1.3% of whole hanging carcasses. Seventy percent of the livers were passed for human food and 14% for pet food; 16% were condemned. Approximately 71% of the liver condemnations were due to liver abscesses. Four percent of the heads, 6% of the tongues, and 0.2% of whole carcasses were condemned. The pregnancy rate in female cattle was approximately 6.7%. The average hot carcass weight was 357 kg (s = 40) in steers, 325 kg (s = 41) in heifers, 305 kg (s = 53) in cows, 388 kg (s = 62) in virgin bulls and 340 kg (s = 39) in mature bulls. The average ribeye area in all cattle was 84 cm2 (s = 12); range 29 cm2 to 128 cm2. Grade fat was highly variable and averaged 9 mm (s = 4) for steers and heifers, 6 mm (s = 6) for cows, 5 mm (s = 1) for virgin bulls, and 4 mm (s = 0.5) for mature bulls. The average lean meat yield was 59.7% in cattle (s = 3.4); range 39% to 67%. One percent of the carcasses were devoid of marbling, 1% were dark cutters, and 0.05% of the steer carcasses were staggy. Six percent of the carcasses had poor conformation, 3.7% were underfinished, and 0.7% were overfinished. Yellow fat was observed in 4% of the carcasses; 10% of carcasses were aged. Based on January 1996 prices, the economic analysis showed that the Canadian beef industry lost $70.52 per head or $189.6 million annually from quality nonconformities. Methods identified to reduce these nonconformities included improvements in management, animal identification, handling, genetic selection, marketing, grading, and information transfer.

Losses over a 2-year period associated with fetal infection with the bovine viral diarrhea virus in a beef cow-calf herd in Saskatchewan

In 1992, significant calf losses occurred between birth and weaning in a 650-cow Saskatchewan beef herd. These losses occurred subsequent to ill-thrift and disease, and every calf necropsied was found to be persistently infected with bovine viral diarrhea virus (BVDV). The objectives of this study were to describe the losses associated with fetal infection with BVDV in this herd and to determine why they occurred. For investigative purposes, blood samples were collected from the entire cow herd and the surviving calves at pregnancy testing in 1992, and tested by virus isolation for BVDV. Between 51 and 71 persistently infected calves were born in 1992. Bovine viral diarrhea virus was only isolated from calves. The only confirmed fetal infections with BVDV were recorded as the birth of persistently infected calves. However, abortions, reduced pregnancy rates, and delayed calvings were also recorded in the cow herd and may have been the result of fetal infections. The herd was monitored again in 1993. Fetal infections with BVDV were recorded as the birth of stunted, deformed, and persistently infected calves. The greatest losses due to fetal infection with BVDV in the 2 years of this study occurred in cows that were 3-years-old at calving (second calves). Bovine viral diarrhea virus appears to have remained endemic in this herd by transmission from persistently infected calves on young 3- and 4-year-old cows to naive calved 2-year-old cows that were mingled with them annually for rebreeding. Significant numbers of the 2-year-old cows remained naive to BVDV, because they were segregated from persistently infected calves at weaning, preventing cross-infection with BVDV.

Protective immunity in cattle following vaccination with conventional and marker bovine herpesvirus-1 (BHV1) vaccines

The efficacy of two experimental subunit gD vaccines and two commercial whole virus vaccines was determined in a bovine herpesvirus-1 (BHV1) challenge trial. Full-length gD and a truncated, secreted form of gD (tgD) were produced using a vaccinia virus expression system and purified by affinity chromatography. Comparison of these forms of gD did not reveal significant structural or antigenic differences. Calves immunized with gD or tgD in avridine developed significantly (P < 0.05) higher neutralizing antibody titers in the serum and nasal mucosa than animals vaccinated with killed virus (KV) or modified live virus (MLV). Following challenge with BHV1, all vaccinated calves had significantly (P < 0.05) lower rectal temperatures and clinical scores than those in the placebo group. In contrast to the KV-, MLV- and placebo-vaccinated calves, the gD and tgD-immunized animals experienced minimal weight loss and virus shedding post-challenge. Glycoprotein B-specific antibodies were detected in KV- and MLV-vaccinated calves, but not in gD- or tgD-immunized animals. These data suggest that full-length or truncated gD, when formulated in an appropriate adjuvant, is more effective than two KV and MLV vaccines and may be used as a marker vaccine for concurrent vaccination and eradication programs of BHV1.

Efficacy of an experimental BHV-1 subunit gIV vaccine in beef calves challenged with BHV-1 in aerosol

Thirty-six beef calves were used to test the efficacy of an experimental truncated BHV-1 glycoprotein (tgIV) vaccine. Calves from 1 source and +/- 1 mo of age were randomly divided into 4 groups: 1) control (adjuvant VSA3), 2) vaccinated with tgIV at 3 and 4 mo of age, 3) vaccinated with tgIV at 3 and 7 mo of age, or 4) vaccinated with tgIV at 6 and 7 mo of age. Calves were challenged with BHV-1 in aerosol (strain 108) at 7 1/2 mo of age. Prior to challenge, serum neutralizing (SN) antibody titers to BHV-1 were significantly (P < 0.05) higher in all vaccinated calves than in controls. Calves vaccinated at 3 and 7, or 6 and 7, mo of age had significantly (P < 0.05) higher SN antibody and nasal antibody titers to BHV-1 and ELISA (enzyme linked immunosorbent assay) titers to gIV at prechallenge than those vaccinated at 3 and 4 mo of age or controls. Postchallenge nasal shedding of BHV-1 occurred only in controls and those vaccinated at 3 and 4 mo of age. Control calves lost significantly (P < 0.05) more weight and had higher sick scores after challenge than those vaccinated at 3 and 7, or at 6 and 7, mo of age. There were strong correlations (P < 0.001) between antibody titers, virus shedding, and sickness.

Regulation of bovine acute phase responses by recombinant interleukin-1 beta

The acute phase response is a collection of physiologic changes initiated early in the inflammatory process. This response is comprised of both localized changes at the site of infection or injury and the initiation of systemic responses, such as the increase in production of acute phase proteins. Cytokines such as interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF) play key roles in the regulation of acute phase response in the species studied to date. To better characterize the acute phase response of cattle, recombinant bovine (rBo). IL-1 beta was administered to cattle. A single administration of rBoIL-1 beta was able to induce a dose dependent increase in body temperature, circulating leukocytes, and serum haptoglobin and fibrinogen concentrations, as well as a decrease in plasma zinc concentration. Five daily administrations of rBoIL-1 beta resulted in heightened and prolonged elevations of haptoglobin and fibrinogen. In addition, alpha 1-acid glycoprotein levels were increased, a response not seen after a single administration of rBoIL-1 beta. These results indicate that IL-1 is an important regulator of the acute phase response in cattle.

Effects of various vaccination protocols on passive and active immunity to Pasteurella haemolytica and Haemophilus somnus in beef calves

Two field trials were conducted in a beef cow herd in Saskatchewan to determine the effectiveness of a combined Pasteurella haemolytica and Haemophilus somnus vaccine in increasing passively and actively acquired antibodies in beef calves. Vaccination of dams at 4 and/or 7 weeks prepartum was associated with increased antibody titers to P. haemolytica and H. somnus in their serum (P < 0.05), colostrum(P < 0.05), and serum of their calves at 3 days and 1 month of age (P < 0.05). There was no significant(P > 0.05) difference in antibody titers in the colostrum and serum of calves from single or double vaccinated dams. Calves vaccinated at 1 and 2 months of age in the face of maternal antibodies toP. haemolytica and H. somnus had significantly(P < 0.05) higher antibodies to P. haemolytica and H. somnus at 4 and 6 months of age than did unvaccinated calves. Calves vaccinated at 3 and 4 months of age in the face of low levels of preexisting antibodies had significantly (P < 0.05) higher antibodies toP. haemolytica at 5 months of age and to H. somnus at 5 and 6 months of age than did unvaccinated calves. Calves vaccinated once at 4 months of age had significantly(P < 0.05) higher antibody titers toP. haemolytica and H. somnus at 4.5 months of age than did unvaccinated calves, but this difference was not apparent at 6 months of age. These results suggest that vaccination of beef cows with a combined Pasteurella haemolytica and Haemophilus somnus vaccine once at 4 weeks prepartum will significantly (P < 0.05) increase passive antibody titers toP. haemolytica and H. somnus in their calves. Double vaccination of calves with preexisting maternal antibodies at 1 and 2 months of age will increase antibody titers to P. haemolytica and H. somnus until 6 months of age. Vaccination of beef calves with low levels of preexisting antibody at 3 and 4 months of age will increase antibody titers to H. somnus until 6 months of age and to P. haemolytica until 5 months of age.However, the level of antibodies achieved by vaccination may depend on the calves being studied, the level of preexisting antibodies, and the efficiency of passive transfer.

Effect of recombinant bovine interleukin-1 beta on viral/bacterial pneumonia in cattle

Bovine herpesvirus-1 (BHV-1) is an important pathogen of respiratory infections in cattle. Its continuing importance lies in its ability to predispose infected hosts to bacterial infections (e.g., Pasteurella haemolytica). In this study we determined whether the immunoregulatory effects induced by recombinant bovine interleukin-1 (rbIL-1) could stimulate appropriate host defense mechanisms to influence the course of BHV-1 and P. haemolytica infection in cattle. We first evaluated the effect of multiple doses (5 doses of 300 ng/kg) of rbIL-1 in normal cattle. An increase in polymorphonuclear (PMN) cells, as well as monocytes, in peripheral blood was observed during the course of IL-1 administration. In addition, the phagocytic activity of monocytes was increased. Although the phagocytic and oxidative burst activities in PMN decreased during the course of rbIL-1 treatment, no changes were observed in the bactericidal capacity of these cells. Lymphocyte numbers in peripheral blood remained unchanged; however, the functional activity of these cells, as measured by IFN-gamma production upon in vitro stimulation, was decreased. In the bovine respiratory disease model, multiple administration of IL-1 did not influence significantly the progression of BHV-1/P. haemolytica infection in cattle. Thus, our results demonstrated that IL-1, although not therapeutically effective, could be administered safely as an adjuvant, even during the course of BHV-1/P. haemolytica infection.

The prevalence of bovine viral diarrhea virus infection in a population of feedlot calves in western Canada

The prevalence of bovine viral diarrhea virus (BVDV) infection was examined in a population of 5129 recently weaned steer calves entering a large feedlot in central Saskatchewan from September to December 1991. Serum samples were collected within 24 h of arrival at the feedlot from every fifth calf processed and again 96 d postarrival. A microtiter virus isolation test was used to determine the prevalence of calves viremic with BVDV on entry to the feedlot. An enzyme-linked immunosorbent assay (ELISA) which detects antibody against glycoprotein 53 of the BVDV was used on paired sera to determine the seroconversion risk during the first 96 d in the feedlot. A virus neutralization (VN) test for BVDV was conducted on a sub-sample of paired sera to measure agreement in determination of seroconversion risk with the ELISA. A polymerase chain reaction (PCR) test which detects BVDV was used to determine if cattle were acutely viremic when treated for disease. The estimated prevalence of persistently infected calves in this population was < 0.1%. The seroconversion risk for BVDV was 27% (236/864) according to the ELISA and it varied from 0 to 63% among the 20 pens sampled. According to the VN test, the seroconversion risk for BVDV was 40% (132/327) and it varied from 0 to 100% among the 11 pens tested. The agreement between the ELISA and VN tests in seroconversion risk to BVDV was very poor (kappa = 0.15 +/- 0.039 SE). The prevalence of acute viremia in calves treated at the feedlot hospital was low at 4% (6/149).(ABSTRACT TRUNCATED AT 250 WORDS)

A subunit gIV vaccine, produced by transfected mammalian cells in culture, induces mucosal immunity against bovine herpesvirus-1 in cattle

A truncated version of bovine herpesvirus-1 (BHV-1) glycoprotein IV (tgIV) was produced in a novel, non-destructive expression system based upon regulation of gene expression by the bovine heat-shock protein 70A (hsp70) gene promoter in Madin Darby bovine kidney (MDBK) cells. In this system, up to 20 micrograms ml-1 of secreted tgIV, which is equivalent to the yield from 4 x 10(6) cells, was produced daily over a period of up to 18 days. Different doses of tgIV were injected intramuscularly into seronegative calves. Virus-neutralizing antibodies were induced by all doses of tgIV, both in the serum and in the nasal superficial mucosa. However, the low dose (2.3 micrograms) induced significantly (p < 0.05) lower antibody titres than the medium (7 micrograms) and high (21 micrograms) doses. The medium and high doses of tgIV conferred protection from BHV-1 infection, as demonstrated by a significant (p < 0.05) reduction in clinical signs of respiratory disease and virus shedding in the nasal secretions postchallenge. However, the 2.3 micrograms group, although partially protected, was not significantly (p > 0.05) different from the placebo group. This study demonstrated the potential of an intramuscularly administered tgIV subunit vaccine to induce mucosal immunity to BHV-1 using an economic protein production system and an acceptable vaccine formulation. In addition, a strong correlation was observed between neutralizing antibodies in the serum and nasal superficial mucosa, virus shedding and clinical disease. Thus, serum neutralizing antibody levels in tgIV-immunized animals may be a good prognosticator of protection from BHV-1 infection and disease.

The occurrence of Haemophilus somnus in feedlot calves and its control by postarrival prophylactic mass medication

Three field trials were conducted in a large commercial feedlot in Saskatchewan to determine the prevalence of Haemophilus somnus in calves and to evaluate the efficacy of prophylactic mass medication with long-acting oxytetracycline on day 17 (1990, n = 1336), day 11 (1991, n = 4372), or day 8 (1992, n = 5632) postarrival. Hemophilosis accounted for > 40% of the mortality in feedlot calves each year. Haemophilus somnus was cultured from the blood of one febrile calf on day 1 (0.1%, n = 895), but it was not cultured from nasal swabs on day 1 or day 11 (n = 881) or from blood samples on day 11 (n = 883). Similarly, it was not cultured from nasal swabs or blood samples from sick calves first treated for bovine respiratory disease (BRD) (n = 219). Serological titers to H. somnus increased (p < 0.05) in unvaccinated calves from day 1 (Geometric mean titer = 11,846) to day 96 (Geometric mean titer = 63,712), indicating natural infection following feedlot entry. Calves that relapsed twice with BRD or died from BRD +/- hemophilosis had significantly (p < 0.06) lower titers to H. somnus on days 1 and 96 than those that did not relapse twice or die. Postarrival mass medication with long-acting oxytetracycline did not reduce (p > 0.05) the risk of hemophilosis mortality. However, it reduced (p < 0.05) the risk of BRD treatment by 14% and the risk of BRD mortality by 71%. Additional epidemiological studies of H. somnus are needed so that we can develop strategic medication and vaccination programs to reduce losses from hemophilosis.

Investigation of an outbreak of mucosal disease in a beef cattle herd in southwestern Saskatchewan

This study describes the epidemiological investigation of an outbreak of mucosal disease that occurred on a ranch in southwestern Saskatchewan. Over a six month period during the fall and winter of 1991-1992,in a herd of 515 beef cattle and 96 bison, 20 yearling cattle from a group of 105 housed in one feedlot pen died from mucosal disease. A further eight yearlings were slaughtered for salvage because they were at risk of dying from mucosal disease. Mucosal disease mortalities were the first observed evidence of fetal infections with bovine viral diarrhea virus in this herd. Animals that died from mucosal disease exhibited signs of ill thrift prior to death. Deaths from mucosal disease were confined to the progeny of one herd of beef cows. Following an outbreak of fetal infection with bovine viral diarrhea virus during 1989-1990, at least 28 (22%) of the 128 calves born from this herd of cows in the spring of 1990 were persistently infected with bovine viral diarrhea virus. However, only one calf born from this herd in 1991, and five calves born from all herds in 1992 were persistently infected. Of the five persistently infected calves born in 1992, three were born to persistently infected replacement heifers born in 1990. These heifers calved without assistance in 1992, but only one of their calves survived past three days of age, and it was persistently infected. In January 1992, 82% of the total herd had reciprocal antibody titers to bovine viral diarrhea virus of >/=1024 which suggested a high level of herd immunity to bovine viral diarrhea virus. Thus, following the outbreak of fetal infection with bovine viral diarrhea virus in 1989-1990, herd immunity to bovine viral diarrhea virus had developed rapidly in the breeding cows and heifers. Subsequently, in the next two years, there was a dramatic decline in the number of calves born persistently infected with bovine viral diarrhea virus.

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

The effect of route and dosage of administration on the serological response to a vaccine containing genetically attenuated leukotoxin of Pasteurella haemolytica combined with bacterial extracts of P. haemolytica and Haemophilus somnus (Somnu-Star Ph, Biostar Inc., Saskatoon, Saskatchewan) was evaluated in a controlled field trial in 301 feedlot calves. Vaccination of calves on arrival at the feedlot with Somnu-Star Ph significantly (p < 0.05) increased P. haemolytica and H. somnus serum antibody titers and reduced bovine respiratory disease (BRD) morbidity. A single subcutaneous vaccination with Somnu-Star Ph was as effective in stimulating a humoral antibody response and in reducing BRD morbidity as double vaccination by the intramuscular or the subcutaneous route. Furthermore, there were no swellings or adverse reactions observed with either subcutaneous or intramuscular administration of Somnu-Star Ph.These results suggest that feedlot calves can be immunized subcutaneously once on arrival with Somnu-Star Ph. Double vaccination was of no added value in this trial, because the majority of BRD morbidity occurred prior to revaccination fourteen days postarrival. Additional larger-sized field trials are needed to monitor the duration of immunity following vaccination and to test the effect of route and dosage of vaccination on mortality.

Epidemiological study of enzootic pneumonia in dairy calves in Saskatchewan

A field study involving 325 calves from 17 dairy herds in Saskatchewan was conducted to determine the risk of enzootic pneumonia and to assess its association with a number of factors. Two different case definitions of pneumonia were used in the analyses: the first was based on producers' treatment risk (CASE1) and the second was based on semimonthly clinical examinations of calves by the research veterinarian (CASE2). The risk of pneumonia based on CASE1 was 39% and on CASE2 was 29%. The measure of agreement between CASE1 and CASE2 at the calf level of analysis was poor (kappa = 0.24, SE = 0.02) and at the herd level of analysis was moderate (kappa = 0.40, SE = 0.12). The mortality risk from pneumonia was 1.8% and a variety of infectious organisms were isolated from pneumonic lungs. Twenty-seven percent of the calves had inadequate (total IgG < or = 800 mg/dL) levels of passively acquired antibodies as measured by radial immunodiffusion. The proportion of seropositive titers in calves within the first two weeks of age was 94% to parainfluenza 3 virus (PI3V) and bovine respiratory syncytial virus (BRSV), 73% to Pasteurella haemolytica (Ph), 68% to bovine viral diarrhea virus (BVDV), 67% to infectious bovine rhinotracheitis virus (IBRV), 46% to Mycoplasma dispar (Md), 44% to Haemophilus somnus (Hs), and 21% to Mycoplasma bovis (Mb). At the calf level of analysis and after adjusting for clustering, there was a negative association (p = 0.10) between the diagnosis of pneumonia based on CASE2 and total IgG levels and Ph titers (rPh).(ABSTRACT TRUNCATED AT 250 WORDS)

The predictive value of pelvimetry in beef cattle

To elucidate reasons for failure of pelvimetry to predict dystocia, we collected data from 1146 heifers and 210 cows in five beef cow herds in Saskatchewan. We assessed the reliability of pelvic area measurements, the generalizability of findings, various modifications of the technique, and the statistical association between pelvic area measurements and dystocia. The repeatability (kappa) of pelvic area measurements between and within veterinarians for the Rice and Krautmann pelvimeters were low to moderate, indicating pelvic area measurements were imprecise. The positive predictive values and sensitivities of pelvic area measurements were consistently poor across herds, years of study, breeds of heifers, times of measurement, various pelvic area cut-off points, and sires. Various modifications of the technique, including pelvic area/calf birth weight ratios, pelvic area/heifer weight ratios, and Ko's calving prediction equation were also poor on-farm tests for predicting dystocia. Although the mean pelvic area in heifers with dystocia was smaller than those without dystocia, there was a large overlap in the distribution of their measurements. Far too many heifers with a small pelvic area had no dystocia (false positives) and far too many heifers with a large pelvic area had dystocia (false negatives) for pelvimetry to be useful. We conclude there is little evidence to justify the continued use of pelvimetry as an on-farm test to reduce dystocia in beef cattle.

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.

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

The efficacy of a Pasteurella haemolytica vaccine (PhV) administered once to calves within 24 hours of arrival at a feedlot was tested for the ability to prevent morbidity and mortality from all bovine respiratory disease (BRD) and specifically from fibrinous pneumonia mortality. The PhV consisted of two immunizing ingredients: outer membrane proteins extracted from P. haemolytica, plus genetically attenuated leukotoxin produced by recombinant DNA technology. This double blind study was conducted at a large Saskatchewan feedlot using 2,324 high-risk calves purchased at auction markets and kept under typical commercial feedlot conditions. The trial design included four vaccine test groups: 1) PhV and a bovine herpesvirus type-1 (BHV-1) subunit vaccine comprised only of the virus glycoprotein IV (gIV); 2) PhV and a commercial modified live vaccine (MLV) containing BHV-1 and parainfluenza-3 viruses; 3) gIV alone; and 4) MLV alone. Calves were assigned to vaccine groups in a random systematic manner, individually identified, and monitored for 90 days after vaccination. The vaccines were given once, on arrival, to reflect common feedlot practice, although vaccination prior to expected risk would be more appropriate.The PhV in combination with gIV reduced BRD morbidity by 20% (p < 0.05) compared to gIV alone and 24% (p < 0.05) compared to MLV alone, and reduced BRD mortality by 88% (p < 0.05) and fibrinous pneumonia mortality by 100% (p < 0.05) when compared to either gIV or MLV alone. Vaccination with PhV in combination with MLV significantly reduced the efficacy of the PhV in preventing BRD morbidity, BRD mortality, and fibrinous pneumonia mortality and also reduced the antibody response to P. haemolytica leukotoxin. These results suggest that the MLV interfered with the protective capacity of the PhV.

Comparative serological response in calves to eight commercial vaccines against infectious bovine rhinotracheitis, parainfluenza-3, bovine respiratory syncytial, and bovine viral diarrhea viruses

A field trial was conducted to compare the serological responses in calves to eight commercial vaccines against infectious bovine rhinotracheitis virus (IBRV), parainfluenza-3 virus (PI3V), bovine respiratory syncytial virus (BRSV), and/or bovine viral diarrhea virus (BVDV). Calves given IBRV, P13V, BRSV, and BVDV vaccines had significantly higher antibodies to these viruses than unvaccinated controls; however, serological responses to killed BVDV vaccines were low. Calves with preexisting antibodies to IBRV, PI3V, BRSV, and the Singer strain of BVDV had lower seroconversion rates following vaccination than calves that were seronegative initially.Serological responses in calves to IBRV, PI3V, BRSV, and BVDV differed among various commercial vaccines. Antibody titers to IBRV were higher in calves vaccinated with modified-live IBRV vaccines than in those vaccinated with killed IBRV vaccines. Following double vaccination with modified-live IBRV and PI3V vaccines, seroconversion rates and antibody titers to IBRV and PI3V were higher in calves vaccinated intramuscularly than in those vaccinated intranasally. Calves given Cattlemaster 4 had significantly higher titers to BRSV and PI3V, and lower titers to BVDV, than calves given Cattlemaster 3, suggesting that the addition of BRSV to Cattlemaster 4 caused some interaction among antigens.

Epidemiological features of calf mortality due to hemophilosis in a large feedlot

Hemophilosis was the most significant cause of mortality in fall-placed calves in a large feedlot in Saskatchewan, despite routine single immunization of calves with a commercial Haemophilus somnus bacterin on arrival. Common manifestations of fatal H. somnus infection were myocarditis and pleuritis; occasionally, thrombotic meningoencephalomyelitis (TME), peracute septicemia, and pneumonia were observed. Circumstantial evidence suggested that H. somnus may be a pathogen in polyarthritis. Death from pneumonia mainly occurred during the first five weeks in the feedlot. Death from myocarditis, pleuritis, TME, and septicemia, and euthanasia because of polyarthritis, occurred mainly after the third week in the feedlot.The median fatal disease onset (FDO) for pneumonia was day 12; for septicemia, day 17; for polyarthritis, day 18; for myocarditis and pleuritis, day 22; and for TME, day 29. Calves that died from myocarditis frequently were found dead in their "home" pen; however, 88% of these animals had been treated previously. Fifty-seven percent of the calves that died from pleuritis were never treated, and those that died from TME or septicemia were either never treated or died shortly after initial treatment.

Campylobacter jejuni abortions in two beef cattle herds in Saskatchewan

Abortions, accompanied by placental retention and weight loss, occurred during February and March in 19% of 120 and 10% of 108 beef cows and heifers on two neighboring ranches in southern Saskatchewan. A diagnosis of Campylobacter jejuni abortion was made based on lesions of necrotizing and suppurative placentitis and fetal bronchopneumonia in association with the culture of large numbers of C. jejuni from placentas and fetal tissues.Campylobacter jejuni was isolated with variable frequency from fecal samples of aborting and healthy cows, and scouring and healthy calves. Campylobacter jejuni serotype 2 (Lior) was isolated from fetal tissues and feces of a scouring calf, whereas C. jejuni serotypes 1, 4, 5 and 99 were isolated from feces of in-contact cattle. We hypothesized that the source and mode of transmission of C. jejuni was fecal contamination of water supplies and feeding grounds by carrier cows or wildlife.

The usefulness of pelvic area measurements as an on-farm test for predicting calving difficulty in beef heifers

Data collected from 197 replacement heifers in four beef cow herds in Saskatchewan were analyzed to determine the usefulness of pelvic area measurements as an on-farm test for predicting calving difficulty.The prevalence of calving difficulty in these herds ranged from 15-34%. Pelvic area measurements prior to the breeding season and at the time of pregnancy examination had poor positive predictive values and sensitivities in each herd. These findings were consistent whether the measurement used as a cut-off point to distinguish between a large and a small pelvic area was the lower 25th percentile, the mean, or the common standard. Standard pelvic area and calf birth weight ratios were not useful in estimating deliverable calf birth weight.Based on these results, pelvic area measurements prior to the breeding season and at the time of pregnancy examination are poor tests for predicting calving difficulty.

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

Five field trials evaluated whether immunization of beef cattle prior to weaning, at weaning, or immediately upon arrival at the feedlot with a commercial bovine respiratory syncytial virus (BRSV) vaccine would reduce subsequent treatment for respiratory disease.Bovine respiratory syncytial virus vaccination was associated with a significant (p<0.05) reduction in treatment rate in one of three groups of calves immunized prior to weaning (-12%) and in calves immunized upon arrival at the feedlot (-4%).There was no significant (p>0.05) effect of the BRSV vaccine on treatment rate in calves immunized at weaning, in calves immunized upon arrival at the Saskatoon bull test station, or in yearlings immunized upon arrival at the feedlot.Although the trend in these field trials was to a sparing effect of the BRSV vaccine, the small reduction in treatment rate may not justify the cost of the vaccination program.

Blindness caused by hypovitaminosis A in feedlot cattle

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