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1. Probiotics are beneficial microbes that are currently considered as alternatives to antimicrobial growth promoters (AGP) in animal nutrition. In addition, they are purported to suppress pathogens in the gut via the concept of competitive exclusion (CE). The aim of this work was to evaluate the efficacy of a multistrain probiotic against Salmonella enteritidis (SE) in broilers. 2. Three hundred and four, one-day-old, male Cobb broilers were fed a corn-soybean basal diet and were allocated to four experimental treatments for 6 weeks. Three of the four treatments were challenged with SE. Treatments were: C- (Negative Control, no SE challenge), C+ (Positive control, SE challenge, no other additives), AB (SE challenge + Avilamycin used as AGP) and PFW (SE challenge + probiotic in feed and water). Morbidity, mortality, incidence of Salmonella positive broilers, cecal microflora composition and antibody response (IgA and IgG) in the blood and intestine were determined as biomarkers of probiotic CE efficacy against SE. 3. The three SE challenged treatments had a significantly higher morbidity compared to C- during the first 2 weeks of age, while there were no differences between treatments regarding mortality. Salmonella shedding was evidenced in 75 and 50% of the birds at 5 and 21 d post-challenge, respectively. Microbiological analysis of cecal digesta in 42-d-old broilers revealed that while broilers in treatment C+ were 100% Salmonella positive, the broilers in treatments PFW and AB were 50% positive and in addition they had lower Salmonella levels (CFU/g digesta) by 27 logs compared to C+. At the age of 42 d significantly higher IgA and IgG specific immune responses against SE were detected at systemic and at intestinal level only for the positive control treatment (C+). 4. In conclusion, the lack of significant levels of specific IgA and IgG against SE at systemic and intestinal level combined with the lower prevalence of SE positive broilers and the lower cecal SE levels in treatments AB and PFW compared to C+, suggest that treatments PFW and AB were efficacious at reducing SE.

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The effect of a dietary phytogenic feed additive (PFA) inclusion level in mucin monosaccharide composition, mucosal morphometry and mucus histochemistry along the broiler intestinal tract was studied. Cobb male broilers (n 5 525) were allocated into five experimental treatments that, depending on the type of addition in the basal diet (BD), were labeled as follows: C (BD based on maize-soybean meal with no other additions), E1 (80 mg PFA/kg BD), E2 (125 mg PFA/kg BD), E3 (250 mg PFA/kg of BD) and A (2.5 mg avilamycin/kg BD). Samples from duodenum, ileum and cecum of 14-and 42-day-old broilers were collected and analyzed. In 14-day-old broilers, treatments E2 and E3 had higher (P , 0.01) duodenal mannose than treatments C, E1 and A. Ileal mannose was lower (P , 0.05) in treatment C compared with PFA treatments, and ileal galactose (Gal) was higher (P , 0.01) in treatments E2 and E3 compared with C and A. Polynomial contrast analysis with respect to PFA inclusion level showed that in 14-day-old broilers there was a linear increase (P 5 0.001) in duodenal mannose and a quadratic effect (P 5 0.038) in duodenal N-acetyl-galactosamine with increasing PFA level. Ileal Gal and mannose increased linearly (P 5 0.002 and P 5 0.012, respectively) with PFA inclusion level. There were no significant differences between treatments in mucin monosaccharide molar ratios of 42-day-old broilers. However, increasing PFA inclusion level resulted in a linear decrease of ileal fucose (P 5 0.021) and cecal N-acetylgalactosamine (P 5 0.036). Experimental treatments did not differ (P . 0.05) regarding duodenal villus height (Vh), crypt depth (Cd) and Vh/Cd ratio, irrespective of broiler age and the intestinal segment examined. However, increasing dietary PFA inclusion level showed a pattern of linear increase of duodenal Vh/Cd ratio in 14-day-old broilers and ileal Vh in 42-day-old broilers (P 5 0.039 and P 5 0.039, respectively). Alcian Blue-Periodic AcidSchiff (pH 2.5) staining of neutral and acidic mucins showed that the staining intensity of mucus layer in villi was fragment (i.e. tip, midsection and base) dependent, whereas in crypts it was dependent both on intestinal segment (i.e. duodenum, ileum and cecum) and fragment. Finally, mucus layer thickness did not differ (P . 0.05) between treatments, yet a pattern of linear increase (P , 0.05) with PFA inclusion level was observed in the duodenum of 42-day-old broilers. In conclusion, the dietary inclusion level of PFA modulated broiler intestinal mucin composition and morphology. Further studies are required to elucidate the physiological implications of such changes in host-microflora interactions.Keywords: phytogenic feed additive, essential oils, broiler, mucin, intestinal morphology ImplicationsThis study has shown that the inclusion level of a phytogenic feed additive in broiler diets has resulted in changes in the gut mucin monosaccharide composition and the intestinal mucosal architecture morphology. Given the fact that animal performance and disease prevention are prerequisite...