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Title: COMPARISON OF FOUR SAMPLING METHODS FOR THE DETECTION OF SALMONELLA IN BROILER LITTER

Author
item Buhr, Richard - Jeff
item Richardson, Larry
item Cason Jr, John
item Cox Jr, Nelson

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2006
Publication Date: 12/26/2006
Citation: Buhr, R.J., Richardson, L.J., Cason Jr, J.A., Cox Jr, N.A. 2006. Comparison of four sampling methods for the detection of salmonella in broiler litter. Poultry Science. 86:(1)21-25.

Interpretive Summary: Three experiments were conducted to compare litter sampling methods in a broiler growout house for the detection of the human bacterial foodborne pathogen Salmonella. For the first experiment, two sets of 25 chicks were challenged orally with a suspension of a marker strain of Salmonella and wing banded for identification, and an additional 25 nonchallenged chicks were placed into each of two challenge pens. At 7, 8, 10, and 11 weeks of age the litter was sampled using four methods: fecal droppings, litter grab, drag swab, and sock; and Salmonella-positive samples were detected in 19% fecal samples, 38% litter grab samples, 44% drag swabs samples, and 44% sock samples. In the second experiment, chicks were challenged with Salmonella upon placement and the litter was sampled at 4, 6, and 8 weeks of age. At these three sampling times, Salmonella was detected in 28% fecal, 56% litter grab, 39% drag swabs, and 84% sock samples. Sock samples had the highest rates of Salmonella detection. In the third experiment, the litter was sampled at 7, 8, and 9 weeks by socks and drag swabs. In addition, comparisons to drag swabs that were stepped on during sampling were made. Both socks (67%) and drag swabs that were stepped on (69%) detected significantly more Salmonella-positive samples than the traditional drag swab (44%) method. Drag swabs that were stepped on had comparable Salmonella detection level to that for socks. Litter sampling methods that incorporate stepping on the sample material while in contact with the litter appear to detect Salmonella in higher incidence than sampling methods dragged over the litter surface. Intermittently stepping on drag swabs during litter sampling will improve sampling detection level for Salmonella without any additional cost.

Technical Abstract: Three experiments were conducted to compare litter sampling methods for the detection of Salmonella. In Experiment 1, two sets of 25 chicks were challenged orally with a suspension of naladixic acid resistant Salmonella and wing banded, and an additional 25 nonchallenged chicks were placed into each of two challenge pens. Fifty nonchallenged chicks were placed into each nonchallenge pen located adjacent to the challenge pens. At 6 wk of age, 12 challenged and 12 nonchallenged broilers from the challenge pens and 12 broilers from each of the nonchallenge pens were sampled for determination of cecal Salmonella status. Broilers remained in the challenge pens throughout the 4-wk litter-sampling period, but were removed from the adjacent nonchallenge pens at 6 wk of age. At 7, 8, 10, and 11 wk of age the litter was sampled using four methods: fecal droppings, litter grab, drag swab, and sock. At 6 wk of age, ceca samples were Salmonella positive from 4/12 challenged broilers and 5/12 nonchallenged broilers raised commingled in the challenge pens, and from 6/24 nonchallenged broilers raised in the nonchallenge adjacent pens. At the four sampling times (from 7 to 11 wk) for the challenge pens, Salmonella-positive samples were detected in 3/16 fecal samples, 6/16 litter grab samples, 7/16 drag swabs samples, and 7/16 sock samples. Samples from the nonchallenge pens were Salmonella positive in 2/16 litter grab samples, 9/16 drag swab samples, and 9/16 sock samples. In Experiment 2, chicks were challenged with Salmonella upon placement and the litter in the challenge and adjacent nonchallenge pens were sampled at 4, 6, and 8 wk of age with broilers remaining in all pens. At the three sampling times for the challenge pens, Salmonella was detected in 10/36 fecal, 20/36 litter grab, 14/36 drag swabs, and 26/36 sock samples. Samples from the adjacent nonchallenge pens were Salmonella positive for 6/36 fecal droppings, 4/36 litter grab, 7/36 drag swab, and 19/36 sock samples. Sock samples had the highest rates of Salmonella detection. In Experiment 3, the litter from a Salmonella-challenged flock was sampled at 7, 8, and 9 wk by socks and drag swabs. In addition, comparisons to drag swabs that were stepped on during sampling were made. Both socks (24/36, 67%) and drag swabs that were stepped on (25/36, 69%) detected significantly more Salmonella-positive samples than the traditional drag swab (16/36, 44%) method. Drag swabs that were stepped on had comparable Salmonella detection level to that for socks. Litter sampling methods that incorporate stepping on the sample material while in contact with the litter appear to detect Salmonella in higher incidence than traditional sampling methods dragging swabs over the litter surface.