Examing Litter Sampling Methodology and the Persistence of Nontyphoidal Salmonella in Reused Poultry Litter
Type of DegreeMaster's Thesis
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Nontyphoidal Salmonella is responsible for a significant proportion of foodborne illness in the United States and is prevalent in broiler houses all over the world. The study of environmental detection methods, management techniques to reduce prevalence, and understanding how Salmonella spp. colonize the GI tracts of broilers is important to establish an understanding of effective measures to control Salmonella spp. in broiler houses. Salmonella Enteritidis (SE) and Salmonella Kentucky (SK) are two widely prevalent serovars isolated in poultry production. Chapter 3 (C3) aimed to compare litter sampling methods in two experiments (C3E1, C3E2) with high (C3E1) and moderate (C3E2) environmental SE prevalence. Methods evaluated included litter grab (LG), drag swabs (DS), roller swabs (RS), and boot covers (BC). Both experiments for S1 involved spreading 800 birds evenly over 32 pens (25 birds/pen). The objective of Chapter 4 (C4) was to examine the effect of untreated control (UC), probiotic blend (PB), sodium bisulfate (SB), sodium formate (SF), and Windrow Compost (WC) treatments on the persistence of SE in broiler houses by using LG, BC, and collecting ceca of market age birds. S2 consisted of four experiments (C4E1-4) with C4E1-C4E3 involving spreading 1000 birds equally over 40 pens (25 birds/pen) and S2E4 involving spreading 1200 over 48 pens due to the addition of 8 fresh bedding (FB) pens. In both C3 and C4 litter sampling was performed between flocks after challenging the first flock with 107cfu/ml at 6 days of age, with each experiment referring to the number of the flock reared in the same pens. The objective of Chapter 5 (C5) was to observe the effects of challenging chicks with 107cfu of SE and/or SK on the colonization of the ceca by either serovar by collecting the ceca at Day 14, 21, 28, 35, 42, and 49 of the first flock (C5E1) and during the second unchallenged flock (C5E2). Treatments in C5 involved challenging with SE before SK (SE/SK), SK before SE (SK), SK only, and SE only challenges. Prevalence data from C3 and C4 were analyzed by chi-squared test or Fisher’s exact test when applicable and differences were observed when P ≤ 0.05. Salmonella counts observed in C4 and C5 were analyzed by GLM with differences observed when P ≤ 0.05 and means were separated with Tukey’s HSD. In C3E1 it was observed that RS were less sensitive in SE detection versus other methods (P<0.0001). However, in C3E2 SE detection using RS was similar in detection to LG, greater than DS (P = 0.022), and lower than BC (P < 0.0001). In C4E1-4 there were no differences observed between treatments in BC detection or cecal colonization although in C4E2 differences were observed in LG sampling between SF and PB (P=0.043) and SB (P=0.001). In C4E1 differences in SE colonization were observed between SE and SK/SE (P=0.44) and differences in SK colonization were observed between SK and SE/SK (P=0.01). Observations in C3 helped further establish environmental detection methods and the potential use of RS for research pens due to the practicality of use. The findings of C4 lead to the potential application of SF as an antimicrobial litter treatment. Additionally, data from C5 demonstrated that the introduction of one serovar of Salmonella spp. negatively affects the colonization of the subsequently introduced serovar in the GI tract of broilers. These findings make significant contributions to the growing body of knowledge concerning the control of Salmonella spp. in broiler houses.