A cross-sectional study of bacterial contamination in plant-protein feed from feed stores in Northern Virginia and Maryland

Prevalence and Antimicrobial Resistance of Salmonella Isolated from Cattle Feces in United States Feedlots in 2011

The objective of this study was to determine the prevalence and characteristics of Salmonella spp. isolated from feces of cattle in feedlots in the United States. Fecal samples were collected from up to three pens of cattle in each of 68 feedlots in 12 states. Samples included up to 25 individual fecal pats from the pen floors and up to five composite samples from the floors of the same pens. The prevalence of Salmonella-positive samples was 9.1% (460/5050) and 11.3% (114/1009) for individual and composite samples, respectively. The prevalences of Salmonella at the pen level were 35.6% (72/202) and 22.8% (46/202) for individual and composite samples, respectively. Dietary factors, including inclusion of cottonseed hulls, coccidiostats, and antimicrobial drugs, were associated with differences in prevalence of Salmonella isolation. Overall, 32 serotypes of Salmonella were identified, but six serotypes accounted for 69.1% (495/716) of the isolates. Nearly two-thirds (64.7%, 44/68) of feedlots had at least one positive sample. All isolates were evaluated for susceptibility to a panel of 15 antimicrobial drugs. Most isolates (74.4%, 533/716) were susceptible to all antimicrobial drugs in the panel. When resistance was detected, it was most commonly to tetracycline (21.7%, 155/716 of isolates) or sulfisoxazole (12.4%, 89/716 of isolates). Less than 10% of the isolates were resistant to any other antimicrobials in the panel. The results of this study indicate that the prevalence of Salmonella in individual fecal samples was less than 10%, but that Salmonella is widely distributed among feedlot cattle. Furthermore, when Salmonella is present in feedlot cattle, there is a low occurrence of antimicrobial resistance with the exception of tetracycline and sulfisoxazole. More research is indicated to understand the ecology of Salmonella and antimicrobial resistance, when present, in cattle-feeding operations.

Survival of Enterococcus faecalis OG1RF:pCF10 in poultry and cattle feed: vector competence of the red flour beetle, Tribolium castaneum (Herbst)

Laboratory experiments were designed to determine the survival of Enterococcus faecalis OG1RF:pCF10 in poultry and cattle feed and its acquisition and transmission by adults of the red flour beetle, Tribolium castaneum (Herbst), to sterile feed. Adult T. castaneum beetles were introduced into poultry and cattle feed inoculated with E. faecalis OG1RF:pCF10 and incubated at 28 degrees C with 65% relative humidity for 7 days in a growth chamber. E. faecalis survived in both poultry and cattle feed during the 7-day test period. There was a logarithmic decrease in E. faecalis concentration in poultry and cattle feed and in and on the insects. E. faecalis persisted on the surface and within T. castaneum adults for 7 days when adults were released on E. faecalis-inoculated poultry feed and for only 5 days on E. faecalis-inoculated cattle feed. The concentration of E. faecalis decreased more slowly on poultry feed than on cattle feed, and this may explain why adult T. castaneum insects were more successful in acquiring and transferring E. faecalis from inoculated poultry feed to sterile poultry feed during the 7-day test period. However, T. castaneum adults reared on inoculated cattle feed were unable to contaminate sterile cattle feed on day 7. To our knowledge, this is the first report documenting T. castaneum to successfully acquire antibiotic-resistant enterococci from animal feed and transfer them to sterile feed. Management of T. castaneum through effective integrated pest management program is therefore important to prevent the spread of antibiotic-resistant and virulent enterococci in animal feed and feed manufacturing environments.

Effects of irradiation of feed ingredients added to meal or pelleted diets on growth performance of weanling pigs

Two experiments were conducted to evaluate the effects of irradiated ingredients in meal and pelleted diets on nursery pig performance. In Exp. 1, a total of 192 pigs (initial BW, 6.0 kg) were used in a 25-d experiment. Pigs were blocked by BW and randomly allotted in a 2 x 2 factorial arrangement of treatments with main effects of diet form (meal or pellet) and either irradiated (11.92 kGy) or nonirradiated spray-dried animal plasma (SDAP). Irradiated SDAP had less total bacterial amounts than nonirradiated SDAP, and pelleted diets also had less bacterial amounts than diets in meal form. However, the complete diets with and without irradiated SDAP had similar bacterial concentrations. There was a diet form x SDAP irradiation interaction (P < 0.05) for ADG from d 0 to 11 and d 0 to 25. Pigs fed irradiated SDAP in meal form had increased ADG compared with pigs fed the nonirradiated meal diet, with no change in ADG of pigs fed pelleted diets. In addition, from d 0 to 11, pigs fed irradiated SDAP or pelleted diets had greater G:F (P < 0.01) compared with pigs fed regular SDAP and meal diets, respectively. In Exp. 2, a total of 350 pigs (initial BW, 4.9 kg) were used in a 22-d experiment to determine the effects of feeding irradiated protein sources (SDAP, soybean meal, fish meal, or all 3) in meal and pellet diets on pig performance. Pigs were blocked by BW and randomly allotted to 1 of 10 treatments consisting of a single diet formulation fed in either meal or pellet form containing either no irradiated protein sources or irradiated SDAP, soybean meal, fish meal, or all 3 irradiated protein sources (10.20 kGy). Irradiated SDAP, soybean meal, and fish meal tended to have reduced total bacterial concentrations compared with nonirradiated plasma, and pelleted diets had reduced bacterial concentrations compared with diets in meal form. No irradiation x diet form interactions (P > 0.16) were observed. From d 0 to 11, pigs fed diets containing irradiated protein sources had greater (P < 0.03) G:F compared with pigs fed the control diets, with no difference in ADG or ADFI. From d 0 to 11, and overall (d 0 to 22), pigs fed pellet diets had greater G:F (P < 0.01) compared with pigs fed meal diets, with no difference in ADG and ADFI. These studies indicate that both irradiation and pelleting are manufacturing processes that can reduce bacteria concentrations in feed ingredients and diets. Irradiated SDAP, soybean meal, and fish meal improved G:F compared with control diets containing nonirradiated ingredients. Furthermore, pigs fed pelleted diets had increased G:F compared with pigs fed meal diets.