The recent trend toward reduction of antibiotic growth promoters (AGP) in North American poultry diets has put tremendous pressure on the industry to look for viable alternatives. In this context, phytogenic feed additives (PFA) are researched to improve gut health and thereby performance. An experiment was conducted with the objective to evaluate the effects of PFA as an alternative to AGP on small intestinal histomorphology, cecal microbiota composition, nutrient digestibility, and growth performance in broiler chickens. A total of 432-day-old Vencobb 400 broiler chicks were randomly assigned to one of three dietary groups, each consisting of 12 replicate pens (n = 12 chicks/pen). The chicks were fed a corn–soybean meal-based control (CON), CON + 500 mg/kg of AGP (bacitracin methylene disalicylate containing 450 mg active BMD/g), or CON + 150 mg/kg of proprietary blend of PFA (Digestarom® Poultry) until 39 days of age when samples were collected. Birds fed either AGP or PFA had increased villus height in all three segments of the small intestine in comparison to the birds fed CON (P ≤ 0.05). Furthermore, the PFA-fed birds had significantly increased villus height and lower crypt depth compared to AGP fed birds (P ≤ 0.05). Birds fed either additive also had increased total tract digestibility of dry matter, crude protein, and ether extract (P ≤ 0.05). The strong effect of the PFA on villus height in the jejunum may suggest augmented nutrient absorption in PFA-fed birds. Although both additives reduced total cecal counts of anaerobic bacteria and Clostridium spp., PFA alone reduced the total coliform count while increasing the Lactobacillus spp. count (P ≤ 0.05). These results suggest the establishment of beneficial microbial colonies in PFA-fed birds. Overall, both PFA and AGP increased body weight gain while lowering the feed conversion ratio (P ≤ 0.05). Hence data from this experiment demonstrate the efficacy of PFA as a substitute to AGP in poultry diets.

Probiotics are live, nonpathogenic microorganisms known to have a positive effect on the host by improving the natural balance of gut microbiota. The objective of this study was to determine the effects of administering probiotics (Primalac W/S) in ovo on hatchability, early post-hatch performance, and intestinal immune-related gene expression of broiler chicks. At embryonic day eighteen, 360 Cobb 500 eggs were injected with sterile water (sham), 1 × 105, 1 × 106, or 1 × 107 (P1, P2, and P3 respectively) probiotic bacteria. Another 90 eggs remained non-injected to serve as a negative control. Measurements and tissue samples were taken on day of hatch (DOH) and days 4, 6, 8, 15, and 22. No significant differences were seen among groups for hatchability, feed intake, feed conversion ratios, or mortality. Body weight of P2 was significantly greater than that of the negative control, sham and P1 on d 4, and that of the negative control and P1 on d 6. A similar pattern was observed for BW gain (BWG) from DOH to d 4. Real-time PCR was used to investigate the expression of immune-related genes in the ileum and cecal tonsils. Other than an initial upregulation of inducible nitric oxide synthase on DOH, in ovo probiotic supplementation was associated with downregulated expression of Toll-like receptors-2 and -4, inducible nitric oxide synthase, trefoil factor-2, mucin-2, interferon-γ, and interleukins-4 and -13 in both the ileum and cecal tonsils, though expression patterns differed based on treatment, tissue, and time point evaluated. Taken together, these results indicate that in ovo supplementation of the probiotic product Primalac does not impact hatchability, can improve performance during the first week post-hatch, and is capable of modulating gene expression in the ileum and cecal tonsils.

In vitro and in vivo experiments were conducted to study the effects of synbiotic supplementation on Salmonella enterica ser. Enteritidis (SE) proliferation, cecal content load, and broiler carcass contamination. Lactobacillus reuteri, Enterococcus faecium, Bifidobacterium animalis, and Pediococcus acidilactici culture supernatants decreased (P < 0.05) the in vitro proliferation of SE at 1:1 supernatant: pathogen dilution. A total of 240 Cobb-500 broiler chicks were randomly allotted to three treatment groups (8 replicates/group with 10 birds/replicate): control (basal diet), antibiotic (Virginiamycin at 20 mg/kg feed), synbiotic (PoultryStar® ME at 0.5 g/kg feed containing L. reuteri, E. faecium, B. animalis, P. acidilactici and a Fructooligosaccharide) from day of hatch. At 21 d of age, all birds in experimental groups were orally inoculated with 250 μl of 1 X 109 CFU SE. Antibiotic supplementation increased (P < 0.05) body weight and feed consumption, compared to the control group. Birds in the synbiotic supplementation had intermediate body weight and feed consumption that were not significantly different from both the control and antibiotic group at 42 d of age in SE infected birds. No significant effects were observed in feed efficiency at 42 d of age among the groups. Antibiotic and synbiotic supplementation decreased (P < 0.05) SE load in cecal contents by 0.90 and 0.85 log units/ g and carcass SE load by 1.4 and 1.5 log units/mL of rinsate compared to the control group at 42 d of age (21 dpi). The relative abundance of IL-10, IL-1, TLR-4, and IFNγ mRNA was decreased (P < 0.05) in the antibiotic and synbiotic supplementation groups compared to the control birds at 42 d of age (21 dpi). It can be concluded that synbiotic supplementation decreased SE proliferation in vitro and decreased SE load in the cecal contents and broiler carcass.

Coccidiosis is regarded as the parasitic disease with the greatest economic impact on the poultry industry due to reduced performance and increased mortality. A study was conducted to investigate the effects of in ovo administration of probiotics on hatchability, performance, immune organ weights, and lesion scores in broiler chicks during a mixed Eimeria infection. At embryonic day 18, 210 eggs were injected with either sterile water or 1×10 cfu probiotic bacteria. On day 3 post-hatch, half of the chicks from each treatment group were challenged with a mixed inoculum of Eimeria acervulina, Eimeria maxima and Eimeria tenella. Measurements and tissue samples were taken on day of hatch (DOH) and days 3, 9 and 15. On day 9, 24 birds per treatment were scored for intestinal Eimeria lesions. No differences were seen among groups for hatchability as well as for body weight (BW), BW gain (BWG), or immune organ weights prior to the Eimeria challenge. On day 9, the non-challenged birds with probiotic supplementation had higher BW and BWG than the non-supplemented controls while no differences were seen among the challenged groups. On day 15, probiotic supplemented birds had improved BW compared to the non-supplemented birds as well as increased BWG from day 9 to 15. Bursa weight was not affected by treatment at any time point while spleen weight was greater in supplemented birds on day 15. Birds receiving the probiotic had significantly lower mortality than non-treated birds. Additionally, gross lesion severity was reduced due to probiotic supplementation in all intestinal segments evaluated. These results suggest that in ovo supplementation of probiotics may improve early performance and provide protection against a mixed Eimeria infection.

Studies were conducted to determine the efficacy of synbiotic applications to combat the negative effects of necrotic enteritis ( NE ). An in vitro study was conducted to test the effect of probiotics species supernatants to decrease Clostridium perfringens ( CP ) proliferation. Lactobacillus reuteri , Enterococcus faecium , Bifidobacterium animalis , and Pediococcus acidilactici culture supernatants decreased the proliferation of CP at 1:1 supernatant-to-pathogen dilution in vitro. Two in vivo studies were conducted to determine the in vivo response of synbiotic supplementation containing the aforementioned probiotic strains on broiler production performance and caecal CP load in broilers induced with NE infection. In experiment 1, 75 broiler chicks were randomly allotted to 3 treatment groups, control (basal diet), ionophore (Salinomycin), and synbiotic (PoultryStar me), from day of hatch, and NE was induced in all birds. There were no significant treatment effects on BW, feed consumption, and feed gain ratio. However, at 35 D, ionophore or synbiotic supplementation increased ( P < 0.05) villi height and decreased interleukin ( IL )-1 mRNA abundance, while synbiotic supplementation increased ( P < 0.05) IL-10 mRNA abundance compared with the control group, respectively. In experiment 2, 360 broiler chicks were randomly allotted to 3 treatments, an unchallenged negative control (control; basal diet), challenged positive control (NE; basal diet), or NE + synbiotic group (synbiotic). At both 21 and 42 D of age, NE birds had decreased ( P < 0.05) BW, feed conversion, and jejunal villi height compared with control, while NE + synbiotic birds were not different from control groups. At 42 D of age, NE birds had 2.2 log/g increased CP in the ceca contents compared with control, while synbiotic birds had CP load that was not different than that of the control group. NE + synbiotic birds had significantly greater amounts of bile anti-CP IgA than the control and NE groups. It can be concluded that synbiotic supplementation decreased CP proliferation in vitro and caecal CP load in vivo while improving production parameters during an NE infection in broilers.