Necrotic enteritis (NE) is a recognized multifactorial disease that cost annually to the poultry industry around $2 billion. However, diverse aspects related to its presentation are not completely understood, requiring further studies using known induction experimental models. Therefore, the purpose of this study was to measure the changes occurring in performance, intestinal integrity and ileal microbiome using a previously established NE-challenge model. Chickens were assigned to a negative control group (NC) or a positive control group (PC). In the PC, broilers were orally gavaged with Salmonella Typhimurium (ST) (1 × 107 cfu/chick) at day 1, Eimeria maxima (EM) (2.5 × 104 oocyst/chick) at day 18 and Clostridium perfringens (CP) (1 × 108 cfu/chick/day) at 23–24 days of age. Weekly, body weight (BW), body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) were evaluated. Morbidity and mortality were determined throughout the study, and NE lesion scores were recorded at day 25. Additionally, blood and liver samples were collected to measure gut permeability as determined by levels of serum fluorescein isothiocyanate-dextran (FITC-d) and bacterial translocation (BT). Ileal contents were processed for 16S rRNA gene-based microbiome analysis. Performance parameters and intestinal permeability measurements were negatively impacted in the PC resulting in elevated serum FITC-d and BT with a −6.4% difference in BWG. The NE lesion score in PC (1.97 vs. 0.00) was significantly higher in comparison to NC, although there was no difference in mortality. The microbiome analysis showed a dramatic shift of ileal microbiomes in PC groups as compared to NC (ANOSIM: R = 0.76, P = 0.001). The shift was characterized by reduced abundance of the phylum Actinobacteria (P < 0.01), and increased abundance of the genera Butyrivibrio, Lactobacillus, Prevotella and Ruminococcus in PC compared to NC (P < 0.05). Expectedly, Clostridium was found higher in PC (2.98 ± 0.71%) as compared to NC (1.84 ± 0.36%), yet the difference was not significant. In conclusion, results of the present study showed the different intestinal epithelial and microbiological alterations occurring in an established NE-challenge model that considers paratyphoid Salmonella infections in young chicks as an important predisposing factor for presentation of NE.

Fluorescein isothiocyanate dextran (FITC-d) is a 3–5 kDa marker used to measure tight junction permeability. We have previously shown that intestinal barrier function can be adversely affected by stress, poorly digested diets, or feed restriction (FR), resulting in increased intestinal inflammation-associated permeability. However, further optimization adjustments of the current FITC-d methodology are possible to enhance precision and efficacy of results in future. The objective of the present study was to optimize our current model to obtain a larger difference between control and treated groups, by optimizing the FITC-d measurement as a biomarker in a 24-h FR model to induce gut permeability in broiler chickens. One in vitro and four in vivo independent experiments were conducted. The results of the present study suggest that by increasing the dose of FITC-d (8.32 versus 4.16 mg/kg); shortening the collection time of blood samples (1 versus 2.5 h); using a pool of non-FITC-d serum as a blank, compared to previously used PBS; adding a standard curve to set a limit of detection and modifying the software’s optimal sensitivity value, it was possible to obtain more consistent and reliable results.

The purpose of this study was to evaluate heat stress as a model to induce gastrointestinal leakage in broiler chickens. On the day of hatch, 320 chicks were allocated into 8 environmental chambers, 4 thermoneutral ( TN ) and 4 continuous heat stress ( HS ). Each chamber was divided into 2 pens containing separate feeders and water jugs (8 replicates per treatment, 20 birds/pen). The environment was established to simulate production setting as best possible for the first 21 D. A gradual reduction of temperature from 32°C to 24°C with relative humidity at 55 ± 5% was adopted for the first 21 D. At the time of HS, the HS groups were exposed to 35°C from Day 21 to 42, while thermoneutral ones were maintained at 24°C from Day 21 to 42. Chickens were equipped with a Thermochron temperature logger for continuous monitoring of core body temperature. The environmental temperature and relative humidity were continuously recorded. Fluorescein isothiocyanate–dextran ( FITC-d ) was orally gavaged to 2 chickens/replicate ( n = 16) randomly selected on days 21, 28, 35, and 42. After 1 h of oral gavage, blood samples were collected to determine the passage of FITC-d. Tibias were removed from all chickens to evaluate break strength only on 21 D and 42 D (before HS and at the end of the trial). Performance parameters were evaluated weekly from 21 D to the end of the trial. Body temperature was significantly ( P < 0.05) increased after 2 h of starting HS and remained that way until the end of the study. Chronic HS caused an increase in core body temperature which decreased feed intake, body weight, and feed efficiency (28, 35, and 42 D) when compared with control TN chickens. Similarly, serum FITC-d was significantly increased in HS chickens at all points of evaluation. Chronic HS also caused a significant reduction of bone strength at 42 D when compared with the control chickens. The results from the present study suggest that HS can be a robust model to induce gut leakage in broiler chickens.

Three experiments were conducted to evaluate the effect of in ovo administration of FloraMax®-B11 (FM) on Marek's disease (MD) herpesvirus of turkeys (HVT) vaccine protective efficacy, hatchability, microbiota composition, morphometric analysis, and Salmonella enteritidis (SE) infection in chickens. Experiment 1 consisted of 3 trials. In trials 1 and 2, d 18 White Leghorn 15I5x71 embryos were randomly distributed in 4 groups: 1) HVT vaccinated in ovo and no Marek's disease virus (MDV) challenge; 2), HVT + FM vaccinated in ovo and no MDV challenge; 3) HVT vaccinated in ovo and challenge with virulent MDV (vMDV; strain 583A); and 4), HVT + FM vaccinated in ovo and challenge with vMDV. Trial 3 was designed exactly the same as Experiment 1 but chicks were challenged with very virulent MDV (vvMDV; strains Md5 and 612). Birds were monitored until 8 wk of age, and tested for MD incidence. Experiment 2 consisted of 3 trials. In each trial, d 18 broiler embryos were injected in ovo with either saline or FM to measure hatchability and gastrointestinal bacterial composition. In Experiment 3, d 18 broiler embryos were injected in ovo with either saline or FM. All chickens that hatched were orally gavaged with SE at hatch and kept for 7 d to monitor post-hatch BW. No significant difference (P > 0.05) between MD percentage in birds vaccinated with HVT alone or HVT + FM were observed in Experiment 1. In Experiment 2, probiotic did not negatively affect hatchability, but did reduce lactose positive Gram-negative bacteria. Further, increase in BW was associated with higher villi surface area in the ileum in chickens that received the probiotic as well as a significant reduction in the SE incidence in Experiment 3. These results suggest that in ovo administration of FM does not negatively impact the ability of HVT to protect against MD or hatchability of chickens, but improves BW during the first 7 d of life and decreases SE recovery in chickens.

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