This experiment was conducted to investigate the effects of Bacillus amyloliquefaciens probiotic (BAP) as a direct-fed microbial on growth performance, cecal microflora, serum immunoglobulin levels, and fecal noxious gas emissions of broiler chickens. A total of 400 one-day-old broiler chicks (Ross 308) were randomly assigned to 1 of 5 treatment diets formulated to supply 0, 1, 5, 10, and 20 g/kg of BAP and were fed for 35 d. Each treatment had 8 replicate pens with 10 birds per replicate. On completion of the growth trial, fecal samples were collected, and ammonia (NH3) and hydrogen sulfide (H2S) emissions were measured. Increasing concentration of BAP had positive linear effect on the ADG of broilers (P < 0.05) throughout the experimental period, with the highest values being observed in broilers offered 20 g/kg of BAP. The ADFI increased linearly (P < 0.02) with the inclusion of BAP during the overall experimental period (d 0 to 35). Providing BAP had a negative linear effect on FCR from d 0 to 21 and d 0 to 35 (P < 0.01). Supplementation with BAP did not affect cecal Lactobacillus and Bacillus content, but exerted negative linear effect on cecal Escherichia coli (P < 0.05) with increasing the level of BAP in broiler diets. Additionally, BAP modified immune response of broilers by linearly increasing serum IgG and IgA (P < 0.01). Dietary BAP resulted in decreased fecal NH3 emissions at 0 (linear, P < 0.001), 3, 6, 12, 24, and 48 h of incubation (linear, P < 0.05; quadratic, P < 0.01). Supplementation of BAP exerted negative linear and quadratic effects on fecal emissions of H2S (P < 0.001) throughout the incubation period except at 48 h, and the optimum effect was found when BAP was provided at 5 g/kg of diet. Based on these results, Bacillus amyloliquefaciens could be suggested as a potential feed additive of broiler diets.

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A study was conducted to evaluate the effects of resveratrol and essential oils from medicinal plants on the growth performance, immunity, digestibility, and fecal microbial shedding of weaned piglets. A total of 48 weaned piglets (8 kg initial weight, 28-d-old) were randomly allotted to four dietary treatments with 3 replications of 4 piglets each. The dietary treatments were NC (negative control; basal diet), PC (positive control; basal diet+0.002% apramycin), T1 (basal diet+0.2% resveratrol), and T2 (basal diet+0.0125% essential oil blend). All piglets were orally challenged with 5 ml culture fluid containing 2.3×108 cfu/ml of Escherichia coli KCTC 2571 and 5.9×108 cfu/ml Salmonella enterica serover Typhimurium. The PC group (p<0.05) showed the highest average daily gain (ADG) and average daily feed intake (ADFI) throughout the experimental period, although feed conversion ratio (FCR) was improved in the T1 group (p>0.05). Serum IgG level was increased in the T1 group, whereas TNF-α levels was reduced in the supplemented groups compared to control (p<0.05). The PC diet improved the dry matter (DM) digestibility, whereas PC and T2 diets improved nitrogen (N) digestibility compared to NC and T1 diets (p<0.05). Fecal Salmonella and E. coli counts were reduced in all treatment groups compared to control (p<0.05). Fecal Lactobacillus spp. count was increased in the T2 group compared to others (p<0.05). Dietary treatments had no significant effect on fecal Bacillus spp. count throughout the entire experimental period. Based on these results, resveratrol showed strong potential as antibiotic alternatives for reversing the adverse effects of weaning stress on growth performance, immunity and microbial environment in E. coli and Salmonella-challenged piglets.

The banning of the use of antibiotics as feed additive has accelerated investigations of alternative feed additives in animal production. This experiment investigated the effect of pure citric acid or acidifier blend supplementation as substitute for antibiotic growth promoters on growth performance, fecal microbial count, and humoral immunity in weaned piglets challenged with Salmonella enterica serover Typhimurium and Escherichia coli KCTC 2571. A total of 60 newly weaned piglets (crossbred, 28-d-old; average 8 kg initial weight) were randomly assigned to four dietary treatments in a completely randomized design. Dietary treatments included NC (negative control; basal diet), PC (positive control; basal diet+0.002% apramycin), T1 (basal diet+0.5% pure citric acid), and T2 (basal diet+0.4% acidifier blend). All piglets were orally challenged with 5 mL of culture fluid containing 2.3×108 cfu/mL of E. coli KCTC 2571 and 5.9×108 cfu/mL of S. typhimurium at the beginning of the experiment. The PC group showed the highest ADG and ADFI, whereas gain:feed was improved in the PC and T1 group (p<0.05). All dietary treatments showed significant reduction in fecal counts of Salmonella and E. coli, compared to NC (p<0.05), with PC being better than T1 and T2. Significant elevation in fecal Lactobacillus spp. counts was shown by treatments with T1, T2, and PC, whereas Bacillus spp. counts were increased by treatment with T1 and T2 compared to NC and PC diet (p<0.05). Serum IgG concentration was increased by T1 diet (p<0.05), whereas IgM and IgA were not significantly affected by any of the dietary treatments (p>0.05). From these above results, it can be concluded that, as alternatives to antibiotics dietary acidification with pure citric acid or acidifiers blend did not fully ameliorate the negative effects of microbial challenges in respect of growth performance and microbial environment, however improved immunity suggested further research with different dose levels.