The aim of this work was to investigate the effect of inclusion levels of a 5-bacterial species probiotic in broiler nutrition. Five hundred twenty-five 1-d-old male Cobb broilers were allocated in 5 experimental treatments for 6 wk. The experimental treatments received a corn-soybean coccidiostat-free basal diet and depending on the addition were labeled as follows: no addition (C), 10(8) cfu probiotic/kg of diet (P1), 10(9) cfu probiotic/kg of diet (P2), 10(10) cfu probiotic/kg of diet (P3), and 2.5 mg of avilamycin/kg of diet (A). Each treatment had 3 replicates of 35 broilers each. Treatment effects on broiler growth performance and biomarkers such as ileal and total tract nutrient digestibility, plasma Ig concentration, and cecal microflora composition were determined. Differences among treatments were considered significant when P < or = 0.05. Overall BW gain was significantly higher in treatment P1 (2,293 g) compared with P2 (2,163 g), C (2,165 g), and P3 (2,167 g), with A (2,230 g) being intermediate and not different from P1. Overall feed conversion ratio values were similar and significantly better for P1 (1.80) and A (1.80) compared with P2 (1.87), C (1.89), and P3 (1.92). Ileal apparent digestibility coefficients (ADC) of CP and ether extract were higher in A. Generally, treatments A and P1 showed an improved total tract ADC for DM, organic matter, ash, ether extract, and AME(n) values. The total tract ADC of CP was higher in P1, C, and P2. There were no differences between treatments regarding plasma Ig in 14- and 42-d-old broilers. Treatments P2 and P3 were effective at beneficially modulating cecal microflora composition. In particular, the lower cecal coliform concentration (log cfu/g of wet digesta) was seen in P2 (6.12) and P3 (4.90) in 14- and 42-d-old broilers, respectively, whereas at 42 d, P3 and P2 had the highest Bifidobacterium (8.31; 8.08) and Lactobacillus concentrations (8.20; 7.86), respectively. It is concluded that probiotic inclusion level had a significant effect on broiler growth responses, nutrient ADC, AME(n), and cecal microflora composition.

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The aim of this work was to assess the effect of dietary viable or heat inactivated probiotic forms (PF) combined or not with avilamycin (AV) used as a growth promoter, on broiler growth performance, nutrient digestibility, digestive enzyme activities, and expression of immune response related genes.Depending on the type of PF (i.e., no addition, viable, inactivated) and AV addition (no/yes), 450 one-day-old Cobb male broilers were allocated in the following 6 treatments according to a 3 × 2 factorial arrangement with 5 replicates of 15 broilers each for 6 wk: CoN: diet without any addition; CoN+A: combination of CoN with AV; ViP: viable PF - no AV; ViP+A: combination of ViP with AV; InP: inactivated PF - no AV; InP+A: combination of InP with AV.There were no interactions (P > 0.05) for overall performance parameters. In contrast, PF or AV addition improved BW gain (PPF= 0.015; PAV < 0.001), FCR (PPF < 0.001; PAV < 0.001) and production efficiency factor (PPF= 0.001; PAV= 0.001).Significant (PPF×AV ≤ 0.05) interaction effects regarding ileal digestibility (IAD) of DM and total tract apparent digestibility (TTAD) of DM and ether extracts (EE) were noted. In addition, PF affected IAD and TTAD of CP (PPF < 0.001, PPF= 0.004, respectively). Inactivated PF increased (PPR= 0.024) lipase activity in jejunal digesta.At spleen level InP and ViP+A down-regulated TGF-β4 (PPF × AV = 0.035) compared to CoN and ViP, whereas ViP+A up-regulated iNOS (PPF × AV = 0.022). An anti-inflammatory effect of live and inactive PF and/or AV addition at cecal tonsils was shown by iNOS down-regulation (PPF × AV= 0.015) compared to CoN. Furthermore, AV down-regulated IFN-γ (PAV= 0.002).In conclusion, viable probiotic, as well as inactivated probiotic alone or in combination with avilamycin, improved nutrient digestibility. All dietary additives affected growth performance positively and induced an anti-inflammatory response at cecal level.

The dietary supplementation of Saccharomyces cerevisiae var. boulardii was evaluated in broilers challenged or not challenged with Salmonella Enteritidis (SE) using a 2 × 2 factorial arrangement. Depending on yeast inclusion at 0 (C) or 1 × 10⁹ cfu/kg diet (Y) and SE challenge (0 or log 6.3 cfu/bird) on d 15, the experiment had four treatments C, Y, C-SE, and Y-SE, respectively. Each treatment had seven replicate floor pens with 15 broilers. Growth performance responses were determined weekly and overall for the 5 week experimental period. Salmonella levels and prevalence in ceca, cloacae, and carcass skin were determined by culture procedures, while cecal microbiota was determined by real time PCR. Yeast supplementation had no effect (PY > 0.05) on growth performance. For the overall post SE-challenge period (i.e., wk 3 to wk 5), Salmonella reduced body weight gain (BWG) (PSE < 0.001), feed intake (FI) (PSE = 0.032), and the European production efficiency (EPEF) factor (PSE = 0.005). Broilers Y-SE had higher (P < 0.001) overall BW gain compared to C-SE ones. Overall mortality was 2.14% and did not differ (P > 0.05) between treatments. Reduced Salmonella levels in the cloacae (P = 0.014) and on the breast skin (P = 0.006) and lower prevalence on the neck skin (P = 0.007) were noted for treatment Y-SE compared to C-SE. Yeast supplementation did not have an effect (P > 0.05) on cecal microbiota composition at d 1 and d 21 post SE-challenge. On the contrary, SE-challenge reduced cecal levels of total bacteria (PSE = 0.002), E. coli (PSE = 0.006), Bifidobacterium spp. (PSE = 0.006), Bacteroides spp. (PSE = 0.010), and Clostridial populations belonging to cluster I and cluster XIVa, (PSE = 0.047 and PSE = 0.001, respectively) on d 1 post SE-challenge. At 21 d post SE-challenge, only the levels of cecal Lactobacillus spp. (PSE = 0.001) and Bifidobacterium spp. (PSE = 0.049) were reduced compared to the non SE-challenged groups. In conclusion, yeast supplementation in SE challenged broilers (Y-SE) was beneficial for growth performance and reduced Salmonella presence compared to C-SE ones. The disturbance of cecal microbiota balance by SE merits further investigation for potential implications in gut and overall bird health.

This study was designed to study the effect of diet supplementation with an organic acids-based formulation (OABF) on luminal- and mucosa-associated bacteria, concentration of volatile fatty acids (VFA), microbial glycolytic enzyme activity and expression of mucin 2 (MUC2), immunoglobulin A (IgA) and tight junction protein, i.e., zonula occludens-1 (ZO1), zonula occludens-2 (ZO2), claudin-1 (CLDN1), claudin-5 (CLDN5) and occludin (OCLN), genes at the ileal and cecal level. A 2 × 2 factorial design was used having OABF inclusion and avilamycin as main factors. Subsequently, 544 day-old male Cobb broilers were allocated in the following 4 treatments, each with 8 replicates: no additions (CON), 1 g OABF/kg diet (OA), 2.5 mg avilamycin/kg diet (AV) and combination of OA and AV (OAAV). The trial lasted for 42 days. In the ileum, OAAV resulted in lower mucosa-associated total bacteria levels (PO × A = 0.028) compared with AV. In addition, ileal digesta levels of Clostridium perfringens subgroup were decreased by avilamycin (PA = 0.045). Inclusion of OABF stimulated the activity of microbial glycolytic enzymes, whereas avilamycin resulted in lower acetate (PA = 0.021) and higher butyrate (PA = 0.010) molar ratios. Expression of ZO1 and CLDN5 was down-regulated by both OABF (PO = 0.016 and PO = 0.003, respectively) and avilamycin (PA = 0.016 and PA = 0.001, respectively). In addition, CLDN1 was down-regulated in AV compared with CON (PO × A = 0.012). Furthermore, OABF down-regulated MUC2 (PO = 0.027), whereas avilamycin down-regulated nuclear factor kappa B subunit 1 (NFKB1) (PA = 0.024), toll-like receptor 2 family member B (TLR2B) (PA = 0.011) and toll-like receptor 4 (TLR4) (PA = 0.014) expression. In the ceca, OABF inclusion increased digesta levels of Clostridium coccoides (PO = 0.018) and Clostridium leptum (PO = 0.040) subgroups, while it up-regulated MUC2 expression (PO = 0.014). Avilamycin (PA = 0.044) and interaction (PO × A < 0.001) effects for IgA expression were noted, with CON having higher IgA expression compared with AV. In conclusion, new findings regarding OABF inclusion effects on an array of relevant biomarkers for broiler gut ecology have been reported and discussed in parallel with avilamycin effects used as a positive control. This new knowledge is expected to provide a response baseline for follow up trials under various stress and challenge conditions.