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  • Author or Editor: Guy H. Loneragan x
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Abstract

Objective—To evaluate the effects of using retentionpond water for dust abatement on performance of feedlot steers and carriage of Escherichia coli O157 and Salmonella spp.

Design—Matched cohort studies.

Animals—2 groups of feedlot steers comprising 3,510 (pathogen carriage) and 3,737 (performance) animals housed in a large commercial feedlot in the Texas Panhandle.

Procedure—Steers were systematically allocated to treatment pens approximately 60 days after arrival (pathogen carriage) or at arrival (performance). For evaluation of pathogen carriage, feces and hide swab specimens were collected from 25 animals in each pen within 10 days of slaughter. Samples were submitted for bacterial culture for E coli O157 and were tested with a polymerase chain reaction-based assay for Salmonella spp. For evaluation of performance, pen weights of animals were obtained at arrival and slaughter and feed delivered to each pen was recorded. The exposure of interest for both studies was application of retention-pond water through fixed high-pressure sprinklers.

Results—Carriage of E coli O157 and Salmonella spp and animal performance were not adversely affected by exposure to retention-pond water. Prevalences of E coli O157 in feces, on hides, and either in feces or on hides for those exposed to retention-pond water were 8.3%, 8.9%, and 15.4%, respectively; prevalences for those unexposed to retention-pond water were 11.4%, 15.4%, and 22.6%, respectively.

Conclusions and Clinical Relevance—Results suggest that use of retention-pond water for dust abatement in feedlot pens does not adversely affect pathogen carriage or animal performance. (J Am Vet Med Assoc 2005;226: 1378–1383)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate site-to-site variation within fecal pats from cattle with regard to detection of Escherichia coli O157 and determine the effect on the accuracy of prevalence estimates of assay of multiple samples collected from the same fecal pat.

Sample Population—120 freshly voided fecal pats collected from 2 beef feedlots.

Procedures—5 samples were systematically collected from each fecal pat and analyzed for E coli O157 via selective preenrichment techniques, immunomagnetic separation, and biochemical tests. Presumptive isolates were definitively identified via agglutination assays and polymerase chain reaction techniques. Best estimators of prevalence were calculated from the distribution of E coli O157–positive samples per pat.

Results—Of the 120 fecal pats, 96, 13, 4, 2, 3, and 2 fecal pats had 0, 1, 2, 3, 4, and 5 E coli O157–positive samples, respectively. The greatest estimate of E coli O157 prevalence (20%) was achieved when all 5 samples were assessed; this estimate represented a 2.4- fold increase in prevalence, compared with that provided via analysis of 1 sample/pat (8.2%). Compared with assessment of 5 sites/pat, the relative sensitivity of detecting an E coli O157–positive fecal pat via analysis of 1 site/pat was 40.1%.

Conclusions and Clinical Relevance—Results suggest that estimates of E coli O157 prevalence derived from sampling of 1 location/pat are likely underestimates of the true prevalence of this pathogen in fecal pats (and by extension, cattle). Additional research is warranted to confirm these results in situations of high and low prevalence and across different feedlots. (Am J Vet Res 2005;66:2023–2027)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate trends in feedlot cattle mortality ratios over time, by primary body system affected, and by type of animal.

Design—Retrospective cohort study.

Animals—Approximately 21.8 million cattle entering 121 feedlots in the United States during 1994 through 1999.

Procedures—Yearly and monthly mortality ratios were calculated. Numbers of deaths were modeled by use of Poisson regression methods for repeated measures. Relative risks of death over time and by animal type were estimated.

Results—Averaged over time, the mortality ratio was 12.6 deaths/1,000 cattle entering the feedlots. The mortality ratio increased from 10.3 deaths/1,000 cattle in 1994 to 14.2 deaths/1,000 cattle in 1999, but this difference was not statistically significant (P = 0.09). Cattle entering the feedlots during 1999 had a significantly increased risk (relative risk, 1.46) of dying of respiratory tract disorders, compared with cattle that entered during 1994, and respiratory tract disorders accounted for 57.1% of all deaths. Dairy cattle had a significantly increased risk of death of any cause, compared with beef steers. Beef heifers had a significantly increased risk of dying of respiratory tract disorders, compared with beef steers.

Conclusions and Clinical Relevance—Results suggested that although overall yearly mortality ratio did not significantly increase during the study, the risk of death attributable to respiratory tract disorders was increased during most years, compared with risk of death during 1994. The increased rates of fatal respiratory tract disorders may also reflect increased rates of non-fatal respiratory tract disorders, which would be expected to have adverse production effects in surviving animals. (J Am Vet Med Assoc 2001;219:1122–1127)

Full access
in Journal of the American Veterinary Medical Association

Objectives

To measure concentrations of thiamine in blood and sulfide in ruminal fluid in cattle with polioencephalomalacia (PEM) and to evaluate temporal associations between PEM and risk factors.

Design

Epidemiologic analysis.

Sample Population

14 steers with acute signs of PEM, 26 clinically normal steers, and records of all cattle in a feedlot for the past 6 years.

Procedures

Concentrations of thiamine in blood and sulfide in ruminal fluid were measured. Values were compared between healthy steers that had been in the feedlot for 3 weeks or 2 months. Records were used to estimate the incidence of PEM and the time when cattle were at greatest risk of developing PEM.

Results

Thiamine concentrations in steers with PEM were within reference ranges. Healthy steers had significantly greater sulfide concentrations 3 weeks after entering the feedlot, when the incidence of PEM was greatest, than 2 months after entering the feed-lot, when risk of developing PEM was low. Thiamine concentrations were within reference ranges at these times. Annually recurrent outbreaks of PEM during the summer began after initiating use of a water well containing a high content of sulfate.

Clinical Implications

Excessive ruminal sulfide production is an important factor in the pathogenesis of PEM, without concurrent thiamine deficiency. Most cases of PEM developed between 15 and 30 days after introduction to a high-sulfur diet. When water is an important source of dietary sulfur, risk of PEM may increase during hot weather. (J Am Vet Med Assoc 1997;211:1275–1279)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine effects of vaccination with siderophore receptor and porin (SRP) proteins derived from Salmonella enterica serotype Newport on milk production, somatic cell count, and shedding of Salmonella organisms in female dairy cattle.

Animals—180 female Holsteins.

Procedures—Cattle were randomly assigned to receive Salmonella Newport SRP vaccine or control solution. Vaccine or control solution was injected 45 to 60 days before parturition, and cattle received a second dose 14 to 21 days before parturition. Milk production was monitored for the first 90 days of lactation. Feces for isolation of Salmonella and blood samples for detection of antibodies against Salmonella Newport were collected at day of first injection and at days 7 to 14 and 28 to 35 of lactation.

Results—Cattle inoculated with Salmonella Newport vaccine produced significantly more milk (1.14 kg/d), compared with cattle injected with the control solution. Cattle administered the vaccine had significantly higher concentrations of circulating antibody against Salmonella Newport SRP proteins at 7 to 14 days and 28 to 35 days of lactation. Salmonella Newport was not recovered; however, Salmonella enterica serotype Agona was recovered from 31 (20.3%) cattle, but likelihood of recovery did not differ significantly between vaccinates and control cattle.

Conclusions and Clinical Relevance—Administration of a vaccine against Salmonella Newport SRP proteins to healthy dairy cattle prior to parturition increased milk production, even in cattle without detectable shedding of Salmonella Newport or clinical signs of salmonellosis. Additional research is needed to clarify the mechanisms by which productivity was improved.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To describe time-dependent changes in plasma concentrations of 3-methylindole (3MI) and blood concentrations of 3-methyleneindolenine (3MEIN)-adduct in feedlot cattle.

Animals—64 yearling steers.

Procedures—Steers were assigned to 2 groups (32 steers/group). During the first 8 weeks, blood samples were collected from group 1 before the morning ration was fed, whereas samples from group 2 were collected 2 to 3 hours after the ration was fed. Blood samples were collected from all steers approximately 4 times/wk for 3 weeks and 3 times/wk for the subsequent 5 weeks. Samples were collected at the same time for all steers for an additional 10 weeks. Plasma samples were analyzed for 3MI concentrations. Blood samples collected from cattle in group 2 during the first 8 weeks were analyzed for 3MEINadduct concentrations.

Results—Mean blood concentration of 3MEINadduct increased to a maximum value on day 33 (0.80 U/μg of protein) and then decreased to a minimum on day 54 0.40 U/μg of protein). Plasma 3MI concentrations initially decreased and remained low until after day 54. Group-1 cattle had lower plasma 3MI concentrations, compared with concentrations for group-2 cattle. Blood 3MEIN-adduct concentrations and plasma 3MI concentrations were not associated with deleterious effects on weight gains.

Conclusions and Clinical Relevance—Blood 3MEIN-adduct concentrations peaked during the period of greatest risk for development of bovine respiratory disease complex. Conversely, plasma 3MI concentrations decreased during the same period. Animal-to-animal variation in metabolic capacity to convert 3MI to 3MEIN may be of more importance than differences in plasma 3MI concentration. Am J Vet Res (2002;63:591–597).

Full access
in American Journal of Veterinary Research

Abstract

Ensuring appropriate animal welfare is a high priority for the beef industry, and poorly defined abnormalities in the mobility of cattle at abattoirs have gained considerable attention recently. During the summer of 2013, abattoirs throughout the United States reported concerns about nonambulatory or slow and difficult to move cattle and cattle that sloughed hoof walls. This report describes various cattle that developed these mobility problems soon after arrival at an abattoir. Affected cattle had various clinical signs including tachypnea with an abdominal component to breathing, lameness, and reluctance to move. Some cattle sloughed 1 or more hoof walls while in lairage pens and were euthanized. Other cattle recovered after being rested overnight. Affected cattle had serum lactate concentration and creatine kinase activity increased from reference ranges. Histologic findings included diffuse necrosis of the epidermal laminae with degenerate collagen and perivascular infiltration of neutrophils in the underlying deep dermis, and were similar for digits that had and had not sloughed the hoof wall. With the exception of the sloughed hoof walls, the clinical signs and serum biochemical abnormalities observed in affected cattle were similar to those observed in pigs with fatigued pig syndrome, and we propose that fatigued cattle syndrome be used to describe such cattle. Although anecdotal evidence generated concern that cattle fed the β-adrenergic receptor agonist zilpaterol hydrochloride were at greater risk of developing mobility problems, compared with cattle not fed zilpaterol, this condition is likely multifactorial. Strategies to prevent this condition are needed to protect the welfare of cattle.

Full access
in Journal of the American Veterinary Medical Association