Project Number: 5438-32000-026-03
Project Type: Trust

Start Date: May 01, 2006
End Date: Apr 30, 2008

Objective:
The objectives are to determine the effects of: (1) feedlot pen surface type (soil vs. pond ash), (2) animal stress-level on the prevalence and levels of E. coli O157:H7 and Salmonella spp. in feces and on hides of the penned cattle, and (3) the effects of feedlot pen surface type (soil vs. pond ash) on the prevalence, levels, and persistence of these pathogens in the manure collected from these two types of pen surfaces.

Approach:
Feedlot heifers of four breeds (hide colors: red, black, tan, and white) will be assigned to one of 16 pens of the MARC feedlot shade research facility. Eight of the 16 pens provide cattle access to shade with a structure covering half of the pen, while the remaining eight pens have no access to shade. Eight of the 16 pens (four shaded and four non-shaded) are surfaced with soil and the remaining eight are surfaced with pond ash. Pens will be stocked at a rate of eight head per pen. Cattle and soil/manure from each pen will be screened for the target pathogens prior to the experiment. Animals will be assigned to pens based upon breed (hide color), weight, and pathogen status. On days 0, 28, 56, and 84 of the experiment, rectal feces, hide, manure, water, and feed samples will be collected from each animal and each pen. Presence and levels of E. coli O157:H7 and Salmonella spp. will be determined in rectal feces (10 g) and hide samples (1000 cm2). Both the presence and levels of E. coli O157:H7, Salmonella spp., generic E. coli, and coliforms will be determined in manure samples collected from four different areas of each pen. E. coli O157:H7 presence will be determined using MRU method enrichment conditions, immunomagnetic separation (IMS), and plating onto ntCHROMagar O157 and ctSMAC. Levels of E. coli O157:H7 will be determined by plating onto ntCHROMagar O157. Presence of Salmonella spp. will be determined using MRU enrichment, IMS, and isolation procedures. Levels of Salmonella spp. will be determined by plating onto XLD agar containing 4.6 ml/L tergitol, 15 mg/L novobiocin, and 5 mg/L cefsulodin. Identities of suspect isolates will be confirmed using standard biochemical, serological, and PCR procedures. Up to three isolates per positive sample will be subjected to PFGE analysis to trace the source(s) of the pathogens. On each sampling day, following the removal of samples for initial analyses, manure samples from each pen will be pooled and mixed, to give one manure pool for each pen for each sampling day. To determine the persistence of the target bacteria in the manure, samples will be collected at 0, 1, 2, 3, and 4 weeks for determination of presence and levels of E. coli O157, Salmonella spp., generic E. coli, and coliforms. Cattle will be weighed, condition scored (including hide cleanliness), and temperament scored on days 0, 28, 56, and 84 of the experiment. On a set schedule, two independent observers will take measurements of respiration rate and panting score twice daily (0800 and 1500) during at least twelve 5-day periods throughout the study. At these same times, standing or lying behavior will also be recorded, and surface temperatures of the soil and pond ash surfaces, both in the shade and in the sun will be recorded. Hide cleanliness will be evaluated and scored for each animal weekly. Feeding behavior will be monitored continuously and animal performance and gain will be calculated. Carcass quality data on individual animals will be collected at slaughter.