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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Nova Microbials DFM and E. coli O157:H7 and Salmonella

Location: Food and Feed Safety Research

Project Number: 3091-32000-030-65
Project Type: Trust

Start Date: Jan 02, 2014
End Date: Aug 12, 2014

Objective:
Determine if two direct-fed microbial (DFM) products are effective against E. coli O157:H7 and Salmonella in experimentally infected cattle.

Approach:
E. coli O157:H7 Experiment - 30 Holstein steers (approx. BW 250 lbs) will be utilized for the experiment. Upon arrival at the laboratory, all steers will be weighed, ear-tagged, wormed, and vaccinated (shipping fever, 7-way). Steers will receive a grass hay and grain diet and be acclimated over a period of 1-2 weeks to an 80% concentrate diet (with Rumensin, 30 g/t) fed at 2.5% of BW. Following acclimation, all steers will be randomly assigned to one of three treatments (10 steers/treatment): control, Nova-Cell (1 billion cfu/hd/d), or experimental probiotic. Treatments will be mixed with the daily feed and animals within a treatment, group fed. Bunk space will be adjusted to allow all animals within a treatment equal access to feed. Dietary treatments will be fed throughout the entire experimental period. On day 32, cattle will be inoculated via oral gavage with overnight culture of a cocktail of three strains of E. coli O157:H7. Fecal shedding of the challenge strains will be monitored three times a week (Mon, Wed, Fri) and 21 days post-inoculation, all animals will be euthanized and necropsied. Tissue and luminal contents will be collected throughout the gastrointestinal tract for culture of the challenge strains of E. coli O157:H7. All samples will be cultured to determine concentrations (quantitative) using a commercial spiral plater and prevalence (qualitative) using an immune-magnetic separation technique. Salmonella Experiment - 30 Holstein steers (approx. BW 250 lbs) will be utilized for the experiment. Upon arrival at the laboratory, all steers will be weighed, ear-tagged, wormed, and vaccinated (shipping fever, 7-way). Steers will receive a grass hay and grain diet and be acclimated over a period of 1-2 weeks to an 80% concentrate diet (with Rumensin, 30 g/t) fed at 2.5% of BW. Following acclimation, all steers will be randomly assigned to one of three treatments (10 steers/treatment): control, Nova-Cell (1 billion cfu/hd/d), or experimental probiotic. Treatments will be mixed with the daily feed and animals within a treatment, group fed. Bunk space will be adjusted to allow all animals within a treatment equal access to feed. Dietary treatments will be fed throughout the entire experimental period. On day 29, blood samples will be collected from all animals for evaluation of innate immune function. On day 32, and subsequently on days 37 and 42, cattle will be inoculated via intradermal injection with Salmonella Montevideo. Two applications of the device will be made, providing 20 injections in each leg, each shoulder (right and left), and side of paunch (right and left). On days 49 and 50 (one week following last inoculation), a second blood sample will be collected (immune function status) and all steers euthanized (one-half of each treatment on each of the two necropsy days). The left and right lymph nodes (popliteal, sub-iliac, and superficial cervical) will be removed and cultured (quantitative and qualitative) for the challenge strain of Salmonella. One isolate from each positive lymph node will be sero-grouped as a method to confirm the isolate is likely the challenge strain.

Last Modified: 10/20/2014
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