Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: James E. Keen x
  • Refine by Access: All Content x
Clear All Modify Search


Objective—To determine whether viable shiga-toxigenic Escherichia coli (STEC) O157 could be isolated from hide surface locations and the oral cavity of finished beef feedlot cattle.

Design—Within-animal prevalence distribution survey.

Animals—139 finished cattle in 4 pens in a feedlot in Nebraska; prevalence of fecal STEC O157 shedding ranged from 20 to > 90%.

Procedure—Samples were collected from 7 sites from each animal: feces, oral cavity, and 5 hide surface locations (lumbar region, ventral aspect of the neck, ventral abdominal midline [ventrum], dorsal thoracic midline [back], and distal aspect of the left hind limb [hock]).

Results—Viable STEC O157 were isolated from the oral cavity or 1 or more hide surfaces of 130 cattle, including 50 fecal isolation-negative cattle. Site-specific prevalence of STEC O157 was 74.8% for oral cavity samples, 73.4% for back samples, 62.6% for neck samples, 60.4% for fecal samples, 54.0% for flank samples, 51.1% for ventrum samples, and 41.0% for hock samples. Only 5 cattle tested negative for STEC O157 at all 7 sites. Multiple correspondence and cluster analyses demonstrated that bacterial culture of feces, oral cavity samples, and back samples detected most cattle with STEC O157.

Conclusions and Clinical Relevance—Results suggest that viable STEC O157 may be isolated from the oral cavity, multiple hide surfaces, and feces of a high percentage of fed beef cattle and that bacterial culture of feces alone generally underestimates the percentage of fed beef cattle from which STEC O157 can be isolated. (J Am Vet Med Assoc 2002;220:xxx–xxx)

Full access
in Journal of the American Veterinary Medical Association


Objective—To estimate prevalence of Salmonella spp in Ohio dairy farms and to identify potential risk factors for fecal shedding of salmonellae.

Design—Cross-sectional study.

Sample Population—105 Ohio dairy farms.

Procedure—Individual fecal samples from all mature cows in study herds were tested for Salmonella spp by use of standard bacteriologic culture procedures. Herds were identified as infected if at least 1 cow was shedding Salmonella spp. Information regarding herd characteristics, management practices, and health history were collected. Potential risk factors for herd-level Salmonella infection were identified.

Results—In 31% of the study herds (95% confidence interval, 22 to 40%), at least 1 cow was shedding Salmonella spp. Six percent of 7,776 fecal samples contained Salmonella organisms; prevalence within infected herds ranged from < 1 to 97%. Herd size, use of free stalls for lactating and nonlactating cows, and use of straw bedding in nonlactating cows were significantly associated with fecal shedding of Salmonella spp, as determined by use of univariate analysis . By use of multivariate analysis, large herds were more likely to be infected than smaller herds; however, no other factors were associated with Salmonella infection after adjustment for herd size.

Conclusions and Clinical Relevance—Subclinical shedding of Salmonella spp is common in Ohio dairy herds, although we could not identify specific interventions that may influence the prevalence of Salmonella spp on dairy farms. It appears that large herd size and intensive management may provide an environment conducive to Salmonella shedding and chronic dairy herd infection. (J Am Vet Med Assoc 2002;220:645–649)

Full access
in Journal of the American Veterinary Medical Association


To evaluate the breeding soundness examination procedure in plains bison bulls.


Multiyear (1993 through 1997) cross-sectional clinical procedure evaluation.


Two hundred thirty-four 28- to 30-month-old bison bulls at Custer State Park


Breeding soundness examinations were performed on all bison bulls using 1992 Society for Theriogenology guidelines for beef cattle semen evaluation and reproductive tract examination. Linear and logistic regression analyses were used to detect correlations and associations among breeding soundness examination variables.


Scrotal circumference (SC) was significantly correlated with body weight, percentage of normal spermatozoa, percentage of primary spermatozoal defects, and percentage of motile spermatozoa. Scrotal circumference was positively associated with increased odds of semen collection, satisfactory motility (≥ 30% motility), satisfactory morphology (≥ 70% normal spermatozoa), and simultaneous satisfactory motility and morphology. Receiver-operator characteristic curve analysis selected 29 cm as the optimal SC cutoff most predictive of simultaneous satisfactory spermatozoal motility and morphology. Only 36.2% (83/229) of the bison bulls had a SC of 29 cm or greater and satisfactory spermatozoal motility and morphology.

Clinical Implications

SC is a good indicator of adequate spermatozoal motility and structure in bison. We recommend use of 30% spermatozoal motility, 70% normal spermatozoal morphology, and 29-cm SC as minimal satisfactory measurements for breeding soundness examinations of 28- to 30-month-old bison bulls that have been raised on forage-based nutrition. (J Am Vet Mec Assoc 1999;214:1212–1217)

Free access
in Journal of the American Veterinary Medical Association


Objective—To describe shiga-toxigenic Escherichia coli O157:H7 (STEC O157:H7) fecal shedding prevalence, seasonal fecal shedding patterns, and site-specific prevalence from the oral cavity, skin, and feces of dairy cattle.

Design—Cross-sectional study.

Animals—Adult dairy cattle from 13 herds in Louisiana.

Procedure—Samples were cultured for STEC O157 by use of sensitive and specific techniques, including selective broth enrichment, immunomagnetic separation, monoclonal antibody-based O:H enzyme immunoassay serotyping, and polymerase chain reaction virulence gene characterization. Point estimates and 95% confidence intervals were calculated for fecal shedding prevalence as well as site-specific prevalence from the oral cavity, skin, and feces. Logistic regression was used to assess seasonal variation and differences at various stages of lactation with respect to fecal shedding of STEC O157 in cattle sampled longitudinally.

Results—Summer prevalence in herds (n = 13) was 38.5%, with a cow-level prevalence of 6.5%. Among positive herds, prevalence ranged from 3% to 34.6%. Samples from 3 of 5 herds sampled quarterly over 1 year yielded positive results for STEC O157. In herds with STEC O157, an increase in cow-level prevalence was detected during spring (13.3%) and summer (10.5%), compared with values for fall and winter. Site-specific prevalences of STEC O157:H7 from oral cavity, skin, and fecal samples were 0%, 0.7%, and 25.2%, respectively.

Conclusions and Clinical Relevance—Our data indicated that STEC O157:H7 was commonly isolated from dairy cows in Louisiana, seasonally shed, and isolated from the skin surface but not the oral cavity of cows. (J Am Vet Med Assoc 2004;224:1151–1158)

Full access
in Journal of the American Veterinary Medical Association


Objective—To compare methods for identification of bulls that were carriers for Tritrichomonas foetus during an outbreak on a large beef ranch and determine whether the percentage of nonpregnant cows was associated with the percentage of bulls infected with T foetus.

Design—Epidemiological study.

Animals—121 Angus and Hereford bulls (1.5 to 6 years old) and 2,960 Angus-cross cows (2.5 to 14 years old) managed as 5 herds on a Nebraska beef ranch.

Procedures—3 sequential preputial scrapings collected from the bulls at 12- to 27-day intervals were cultured, and cultures were examined for live T foetus daily for 5 days. On day 5, aliquots of the culture fluid were tested by means of T foetus-specific gel and real-time PCR assays. Cows were tested for pregnancy by means of rectal palpation.

Results—For 361 preputial scrapings obtained from 121 bulls, results of culture and gel PCR assay were in close agreement. The real-time PCR assay had similar sensitivity to culture and the gel PCR assay but generated more false-positive results. Twenty-four of the 121 (19.8%) bulls were identified as infected with T foetus. For the 5 ranch herds, there was a positive linear correlation between percentage of infected bulls (range, 0% to 40%) and percentage of nonpregnant cows (range, 8.3% to 19.2%).

Conclusions and Clinical Relevance—Results suggested that a combination of culture and the gel PCR assay performed on 3 sequential preputial scrapings was the best method for identifying bulls that were carriers for T foetus during this herd outbreak.

Full access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association


Objective—To evaluate associations between neonatal serum IgG1 concentration and pre- and postweaning morbidity and mortality rates and average daily gains (ADGs) in beef calves and define a cutoff point for serum IgG1 concentration necessary for optimal health and performance of beef calves.

Design—Nonconcurrent cohort study.

Animals—1,568 crossbred beef calves.

Procedure—Single radial immunodiffusion was used to quantitate IgG1 concentration in sera collected from calves between 24 and 72 hours after birth. Logistic regression, ANCOVA, and likelihood ratios were used to analyze data.

Results—In the preweaning period, lower perinatal IgG1 concentrations were significantly associated with higher morbidity rates, higher mortality rates, and lower ADGs. Calves with serum IgG1 concentration < 2,400 mg/dL were 1.6 times as likely to become ill before weaning and 2.7 times as likely to die before weaning as calves with higher serum IgG1 concentrations. Calves with serum IgG1 concentration of at least 2,700 mg/dL weighed an estimated 3.35 kg (7.38 lb) more at 205 days of age than calves with lower serum IgG1 concentration. No significant association of serum IgG1 concentration with feedlot morbidity, death, or ADG was identified.

Conclusions and Clinical Relevance—By use of likelihood ratios, the threshold of serum IgG1 concentration for optimal health and performance of calves was higher than values reported previously. Implementation and maintenance of management and intervention strategies designed for early detection and treatment of calves at risk for failure of passive transfer will likely result in increases in preweaning health and performance parameters.

Full access
in Journal of the American Veterinary Medical Association


Objective—To determine whether a selected set of 20 single nucleotide polymorphism (SNP) markers derived from beef cattle populations can be used to verify sample tracking in a commercial slaughter facility that processes primarily market (ie, culled) dairy cows.

Design—Prospective, blinded validation study.

Animals—165 cows and 3 bulls from 18 states (82% Holstein, 8% other dairy breeds, and 10% beef breeds).

Procedure—Blood was collected by venipuncture from randomly chosen animals just prior to slaughter. The purported corresponding liver samples were collected during beef processing, and genotype profiles were obtained for each sample.

Results—On the basis of SNP allele frequencies in these cattle, the mean probability that 2 randomly selected individuals would possess identical genotypes at all 20 loci was 4.3 × 10-8. Thus, the chance of a coincidental genotype match between 2 animals was 1 in 23 million. Genotype profiles confirmed appropriate matching for 152 of the 168 (90.5%) purported bloodliver sample pairs and revealed mismatching for 16 (9.5%) pairs. For the 16 mismatched sample pairs, 33% to 76% of the 20 SNP genotypes did not match (mean, 52%). Discordance that could be attributed to genotyping error was estimated to be < 1% on the basis of results for split samples.

Conclusions and Clinical Relevance—Results suggest that this selected set of 20 bovine SNP markers is sufficiently informative to verify accuracy of sample tracking in slaughter plants that process beef or dairy cattle. These or similar SNP markers may facilitate high-throughput, DNA-based, traceback programs designed to detect drug residues in tissues, control of animal diseases, and enhance food safety. (J Am Vet Med Assoc 2005;226:1311–1314)

Full access
in Journal of the American Veterinary Medical Association