The effect of bovine leukemia virus on dairy cow longevity.

Bovine leukemia virus (BLV) is a retrovirus of cattle that infects approximately 45% of all US dairy cattle, with about 90% of US dairy herds having at least one infected animal. Studies have found BLV infection to be associated with multiple measures of decreased immune function, which may explain the observed economic losses from milk production, decreased cow longevity, and predisposition to lymphoma and other diseases. Our objective was to measure the association between BLV infection and cow longevity in dairy cow operations.

Impact of bovine leukemia virus infection on beef cow longevity.

Bovine leukosis is a chronic lymphoproliferative disorder caused by bovine leukemia virus (BLV). Previous studies estimate that 38 % of cow-calf beef herds and 10.3 % of individual beef cows in the US are BLV seropositive.

Breeding bulls as a potential source of bovine leukemia virus transmission in beef herds.

Objective: To determine the prevalence of bovine leukemia virus (BLV) in beef bulls; evaluate the presence of BLV provirus DNA in blood, smegma, and semen samples; and analyze whether blood BLV proviral load was associated with differential blood cell counts.

Design: Observational cross-sectional study.

Animals: 121 beef bulls ≥ 2 years old from 39 Michigan herds.

Survival of Mycobacterium bovis during forage ensiling.

OBJECTIVE To determine whether Mycobacterium bovis remains viable in ensiled forages. SAMPLE Alfalfa, mixed mostly grass, and corn silages. PROCEDURES For each of 10 sampling days, six 250-g replicate samples of each feedstuff were created and placed in a film pouch that could be vacuum sealed to simulate the ensiling process.

Lack of Bovine leukemia virus transmission during natural breeding of cattle.

Bovine leukosis is a chronic lymphoproliferative disorder that leads to significant economic losses in the beef and dairy industries. The major route of virus transmission is believed to be iatrogenic through the transfer of blood containing infected lymphocytes. In addition, BLV proviral DNA has been identified in nasal secretions, saliva, milk, colostrum, semen and smegma; however, natural transmission of BLV through these secretions has not been clearly demonstrated.

Comparing the Genetic Diversity and Antimicrobial Resistance Profiles of Recovered from Cattle and Humans.

, a leading cause of gastroenteritis in humans, is a foodborne pathogen that can reside in chickens, pigs, and cattle. Because resistance to fluoroquinolones and macrolides, which are commonly used to treat human infections, has emerged in , it is imperative to continously monitor resistance patterns and examine the genetic variation in strains from human infections and animal reservoirs. Our previous study of from human campylobacteriosis cases showed a significantly higher rate of tetracycline resistance compared to national trends, and identified multilocus sequence type (ST)-982 and a history of cattle contact to be associated with tetracycline resistance.

Effect of feeding a direct-fed microbial on total and antimicrobial-resistant fecal coliform counts in preweaned dairy calves.

Objective: To determine whether feeding a direct-fed microbial (DFM) to dairy calves would reduce total and antimicrobial-resistant coliform counts in feces and affect average daily gain (ADG).

Animals: 21 preweaned Holstein heifer calves.

Procedures: The study had a randomized complete block design.

Indoor Confined Feedlots.

Indoor confined feedlots offer advantages that make them desirable in northern climates where high rainfall and snowfall occur. These facilities increase the risk of certain health risks, including lameness and tail injuries. Closed confinement can also facilitate the rapid spread of infectious disease.

Detection of bovine respiratory syncytial virus infections in young dairy and beef cattle in Poland.

Background: Bovine respiratory syncytial virus (BRSV) is a major contributor to bovine respiratory disease complex in dairy and beef calves, especially during the first year of life. There is a lack of comprehensive information about the prevalence of infection in cattle herds in Poland as well as in European countries outside the European Union.

Objective: The aim of this study was to estimate the prevalence of BRSV infections in young beef and dairy cattle in southeastern Poland, a region that has direct contact with non-EU countries.

Options for the control of bovine leukemia virus in dairy cattle.

The subclinical impact of bovine leukemia virus (BLV) on the sustainability of the US dairy industry is only now being fully recognized. Findings of recent longitudinal studies conducted in Michigan dairy herds were consistent with the results of previous studies in showing that within-herd prevalence of BLV-infected cattle was negatively associated with milk production and cow longevity. Risk factors relating to routes of hematogenous transmission such as the use of shared hypodermic needles, shared reproductive examination sleeves, and natural breeding were associated with BLV within-herd prevalence.

Effect of constant exposure to cattle persistently infected with bovine viral diarrhea virus on morbidity and mortality rates and performance of feedlot cattle.

Objective: To determine the effects of constant exposure to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) on health and performance of feedlot cattle.

Design: 3 controlled trials.

Animals: Crossbred feedlot cattle (trial 1, n = 184; trial 2, 138; trial 3, 138).

Review of the Michigan Upper Peninsula bovine viral diarrhea virus eradication project.

Objective: To evaluate the effects of a voluntary regional bovine viral diarrhea virus (BVDV) control project implemented in the Upper Peninsula of Michigan.

Design: Longitudinal study. Sample-294 cattle producers and 11,917 cattle from the Upper Peninsula.

Effect of transportation, time of sampling, and lymphocyte numbers on gamma interferon response to Mycobacterium bovis in cattle at time of slaughter.

Adapting the gamma interferon (IFNγ) assay for tuberculosis screening at points-of-concentration of cattle would improve global efforts to eradicate bovine tuberculosis. Two separate studies were conducted to evaluate if transportation of cattle, the time of blood collection, and total lymphocyte count affects the retention of a positive IFNγ assay result during slaughter of cattle experimentally sensitized with inactivated Mycobacterium bovis. Study 1 evaluated IFNγ assay responses to M.

Differential gene expression segregates cattle confirmed positive for bovine tuberculosis from antemortem tuberculosis test-false positive cattle originating from herds free of bovine tuberculosis.

Antemortem tests for bovine tuberculosis (bTB) currently used in the US measure cell-mediated immune responses against Mycobacterium bovis. Postmortem tests for bTB rely on observation of gross and histologic lesions of bTB, followed by bacterial isolation or molecular diagnostics. Cumulative data from the state of Michigan indicates that 98 to 99% of cattle that react positively in antemortem tests are not confirmed positive for bTB at postmortem examination.

Detection of interferon-γ response to tuberculosis in blood collected at commencement of exsanguination at slaughter from cattle sensitized with Mycobacterium bovis.

Objective: To determine whether an interferon (IFN)-γ response sufficient to categorize cattle as positive for tuberculosis can be detected in blood collected at commencement of exsanguination at slaughter.

Animals: 15 Holstein cows.

Procedures: 12 cows were experimentally sensitized by SC injection with inactivated Mycobacterium bovis in mineral oil, which induced an immune response that mimicked natural infection with M bovis.

Evaluation of skin samples for bovine viral diarrhea virus by use of reverse transcriptase polymerase chain reaction assay after vaccination of cattle with a modified-live bovine viral diarrhea virus vaccine.

Objective: To determine whether vaccine virus can be detected by use of reverse transcriptase (RT)-PCR assays for pooled and individual skin samples obtained from cattle after vaccination with a commercially available modified-live bovine viral diarrhea virus (BVDV) vaccine.

Animals: 12 BVDV-seropositive steer calves and 7 BVDV-seronegative (antibody titer < 1:4) heifers; all cattle were free of persistent infection with BVDV.

Procedures: 2 experiments were conducted.

Use of sentinel serology in a Bovine viral diarrhea virus eradication program.

Forty-seven cattle management groups from 36 herds in a regional Bovine viral diarrhea virus (BVDV) eradication program were selected to evaluate serology as a tool to detect herd infection with BVDV. Serum samples were obtained from 5 non-vaccinated sentinel calves ≥ 6 months old in each management group and virus neutralizing (VN) antibody titers against BVDV genotypes 1 and 2 were determined. A herd was considered positive if 2 or more sentinel calves had VN antibody titers ≥ 128 to either genotype.

Descriptive epidemiology of bovine tuberculosis in michigan (1975-2010): lessons learned.

Despite ongoing eradication efforts, bovine tuberculosis (BTB) remains a challenge in Michigan livestock and wildlife. The objectives of this study were to (1) review the epidemiology of BTB in Michigan cattle, privately owned cervids, and wildlife between 1975 and 2010 and (2) identify important lessons learned from the review and eradication strategies. BTB information was accessed from the Michigan BTB Eradication Project agencies.

Longitudinal study of the distribution of Mycobacterium avium subsp. paratuberculosis in the environment of dairy herds in the Michigan Johne's disease control demonstration herd project.

The objective of this study was to describe the distribution of Mycobacterium avium subsp. paratuberculosis (MAP) in the environment of infected dairy farms over time. Johne's disease (JD) prevalence was monitored annually in 7 Michigan dairy herds.

Innovations in food-supply veterinary medicine: the michigan state university college of veterinary medicine summer food systems fellowship program.

The purpose of this article is to outline a new educational model at Michigan State University's College of Veterinary Medicine. The Summer Food Systems Fellowship Program provides opportunities for food industry-oriented students to experience summer employment with agriculture industry partners, and gives the industry partners exposure to the veterinary profession.

Changes in antibiotic susceptability of Escherichia coli isolated from steers exposed to antibiotics during the early feeding period.

The influence of therapeutic choices on antibiotic resistance of intestinal bacteria may have food safety consequences. Changes in antibiotic susceptibility of Escherichia coli to antibiotics currently approved for prevention and treatment of bovine respiratory disease were evaluated in 260 feedlot steers. Susceptibilities to antimicrobial compounds were compared among three treatment groups at three times between arrival at the feedlot and harvest to assess changes over the course of the feeding period.

Fetal protection against continual exposure to bovine viral diarrhea virus following administration of a vaccine containing an inactivated bovine viral diarrhea virus fraction to cattle.

Objective: To evaluate the efficacy of a commercially available killed bovine viral diarrhea virus (BVDV) vaccine to protect against fetal infection in pregnant cattle continually exposed to cattle persistently infected with the BVDV.

Animals: 60 crossbred beef heifers and 4 cows persistently infected with BVDV.

Procedures: Beef heifers were allocated to 2 groups.

Acute anhydrous ammonia intoxication in cattle.

Intoxication with anhydrous ammonia (AA) is a common occupation-related health problem affecting farmers and fertilizer applicators, however, very few descriptions of animal exposure to this toxicant exist. Thieves entered a feedlot and damaged a liquid AA storage tank, resulting in the accidental leakage of gas from a valve. Overnight, 12 cattle were found dead, with a total mortality of 64 cattle out of 260 on the premises dying or euthanized in < 1 week.

Reproductive losses caused by bovine viral diarrhea virus and leptospirosis.

Bovine viral diarrhea virus and Leptospira spp. are two of the common pathogenic organisms responsible for reproductive losses in cattle worldwide. Both can be come endemic in herds resulting in chronic low-grade reproductive losses or they can be introduced into relatively naïve herds, resulting in substantial reproductive losses over a short period of time.

Platelet function and association of bovine viral diarrhea virus with platelets of persistently infected cattle.

Objective: To determine whether viral involvement with platelets obtained from cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) is associated with altered platelet function or decreased platelet counts.

Sample Population: Platelets obtained from 8 cattle PI with BVDV and 6 age-, sex-, and breed-matched uninfected control cattle.

Procedure: Manual platelet counts were determined, and platelet function was assessed through optical aggregometry by use of the aggregation agonists ADP and platelet-activating factor.