A systematic review-meta-analysis and meta-regression on the effect of selected competitive exclusion products on Salmonella spp. prevalence and concentration in broiler chickens.

The effectiveness of various competitive exclusion (CE) products for reducing Salmonella colonization in broiler chickens was evaluated using systematic review-meta-analysis-meta-regression (SR-MA-MR). Relevance screening identified 201 relevant studies that were subjected to methodological assessment. Of these studies, 159 were suitable for data extraction, 66 were presented in a number of MAs and 130 were examined in a meta-regression (MR). Fourteen different CE products were identified, 9 of them commercial products, and the most common route of administration was oral gavage (63.7% of trials). Meta-analyses indicated that a number of CE products reduce Salmonella colonization in broilers, the most effective one being Preempt™ which was formerly known as CF-3. Five study characteristics (publication year, CE type, CE route, sample origin, and Salmonella serovar administered/recovered) and three methodological soundness characteristics (treatment assignment, intervention and laboratory methods description) were retained as statistically significant (p<0.05) in the final MR model. The MR analysis indicated that, undefined CE products outperformed all commercial products, except for: Preempt™ and Broilact(®). Both were considered comparable to the undefined chicken source CE culture products in effectiveness. The administration of CE through spraying the chicks at the hatchery was determined to be just as effective as the oral gavage treatment, and more practical for farmers to administer. The results of this study could be useful in decision-making concerning the on-farm use of CE products in broiler chickens, and as inputs for risk assessments as the industry pushes for more antibiotic-free alternatives. Out of the various interventions to reduce Salmonella colonization in broilers on-farm, CE was the most studied; its inability to be licenced in certain countries and proof of consistent efficacy remains a barrier.