Subclinical Necrotic Enteritis Challenge Research Articles

241 Immunophysiology and performance of broilers supplemented with macroalgal sulfated polysaccharides during a subclinical necrotic enteritis challenge

Abstract This study evaluated the effects of a sulfate polysaccharide extracted from marine algae product on performance, intestinal lesion scores, and mRNA abundance of various tight junction proteins and immune response genes. A total of 600 one-day old male broilers (Ross 708) were allocated to one of four treatment groups (6 replicate floor pens, 25 birds/pen): negative control (NC) group fed a corn-soybean meal diet; positive control (PC) fed NC + 15 ppm Avilamycin and 125 ppm Amprolium, an additive group (AGS) fed NC + Algoguard added at 0.1% of the diet, and (AGH) fed NC + Algoguard added at 0.2% of the diet. To predispose the birds to NE, birds were orally gavaged with 2,000 Eimeria maxima sporulated oocysts on d 14 followed by a dose of approximately 1×108 CFU/mL of C. perfringens on d 19. On d 21, four birds/pen were necropsied for NE lesions and on d 14, 21, and 42 jejunal samples were collected to assess mRNA abundance. Birds and feed were weighed on d 14, 21, 28, and 42 on a per pen basis. Average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) were calculated during each feeding phase and adjusted for daily mortality. The data were analyzed using ANOVA (JMP, Pro 16) and significance (P ≤ 0.05) was determined by the LSD test. During d 14-21, 0-21, 0-28, and 0-42, mortality rate and ADFI were significantly less in AGS, AGH, and PC compared with NC. ADG was greater while FCR was significantly less in PC, AGS, and AGH during d 21-28, 0-28, and 0-42 compared with NC (P ≤ 0.05). Lesion severity was also significantly less in AGS, AGH, and PC compared with NC. On d 14, 21, and 42 there were no toxins present in the tested serum samples. Calprotectin concentration was greater in PC and NC on d 21 and 42 compared with the supplemented groups. C. perfringens toxin was not detected in serum samples of any of the four treatment groups. mRNA abundance of CLDN1, IL1β, IL12B, and IL10 was greater in AGS compared with NC on d 14 and 42. ZO1 was significantly greater on d 21 in PC treatment and was less than both AGS and AGH on d 42 (P ≤ 0.05). Compared with all other treatments, mRNA abundance of OCLDN was greater and those of IFN-γ and ZO2 were less in PC, while that of CLDN3 showing no significant difference among all 4 treatments. To conclude, dietary inclusion of this algal product in broiler diets could be considered as a beneficial alternative to antibiotic growth promoters in the context of this challenge model.

Ileal profile of non-starch polysaccharides and oligosaccharides in response to exogenous enzymes in broiler chickens offered wheat- or maize-based diets under subclinical necrotic enteritis challenge.

The present study evaluated the impacts of fibre-degrading enzymes on the profiles of non-starch polysaccharides (NSP) and oligosaccharides (OS) in the ileum of broiler chickens offered wheat- or maize-based diets under subclinical necrotic enteritis (NE) challenge. A 2 × 2 × 4 factorial arrangement of treatments was used. Factors were the following: NE challenge, no or yes; diet type, wheat- or maize-based; and supplemental enzymes, control (no enzyme), family 10 xylanase (XYN10), family 11 xylanase (XYN11) or β-mannanase (MAN). Birds in the challenged group were inoculated with Eimeria on d 9 and Clostridium perfringens on d 14 and 15. A 3-way interaction (P = 0.047) occurred on overall (d 0 to 16) weight gain. When NE was present, all the supplemental enzymes increased weight gain in birds fed the wheat-based diet; whereas in those fed the maize-based diet supplemental XYN10 and XYN11 decreased weight gain. When NE was absent, birds fed the wheat-based diet supplemented with XYN10 or MAN presented increased weight gain compared to non-supplemented birds, but no improvements with enzyme addition were observed in birds fed the maize-based diet. A 3-way interaction (P = 0.002) was observed on insoluble NSP level in the ileum. When NE was absent, all the supplemental enzymes reduced the ileal level of insoluble NSP, regardless of diet type. In the challenged birds, supplementing XYN10 and MAN reduced insoluble NSP level in the ileum, but only in birds fed the wheat-based diet. Ileal soluble NSP level was reduced by supplemental XYN11 and MAN, but only in birds fed the wheat-based diet, resulting in a 2-way diet type × enzyme interaction (P < 0.001). Ileal OS arabinose (P = 0.030) level was highest in birds offered the wheat-based diet supplemented with XYN11. Collectively, supplementation of NSP-degrading enzymes to the wheat-based diet enhanced bird performance regardless of NE challenge, with XYN11 significantly increasing oligosaccharide release. However, enzyme addition did not improve growth performance in birds fed maize-based diet, with supplemental XYN10 and XYN11 impeding weight gain when NE was present.

Trans-anethole Ameliorates Intestinal Injury Through Activation of Nrf2 Signaling Pathway in Subclinical Necrotic Enteritis-Induced Broilers.

This study was conducted to investigate the alleviative effects of trans-anethole (TA) on intestinal oxidative stress by enhancing the activities of intestinal antioxidant enzymes and activating the Nrf2 signaling pathway in subclinical necrotic enteritis (NE) infected broilers. A total of 192 1-day-old male Arbor Acres broilers were randomly allocated into three treatment groups: (1) control (CON); (2) subclinical NE challenge (NE); (3) NE challenge + 600 mg/kg TA (NE+TA600). Subclinical NE was induced by oral administration of live coccidiosis vaccine containing 2 × 104 oocysts at 10 days of age and 2 ml of Clostridium perfringens type A solution (3 × 108 CFU/ml) daily from days 14 to 19. The results showed that NE infection led to a severe decline (p < 0.05) in the final body weight (BW) and average daily gain (ADG), but an increase (p < 0.05) in feed/gain (F/G) of broilers at day 10–21 and day 1–21 compared with the control group. TA administration improved (p < 0.05) the growth performance of NE birds. The intestinal villus height (VH) and villus height/crypt depth (VH/CD) were reduced (p < 0.05) by NE challenge as compared with those of the control group, which was elevated by TA administration. Subclinical NE infection decreased (p < 0.05) serum activities of total superoxide dismutase (T-SOD), total antioxidant capacity (T-AOC), and jejunal and ileal glutathione peroxidase (GSH-PX), and T-SOD activity as well as T-AOC in the jejunum, while TA interventions positively elevated that (p < 0.05). Administration of TA protected the intestine against oxidative stress through up-regulation of intestinal nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway as compared with the NE group (p < 0.05). In addition, dietary inclusion of TA elevated (p < 0.05) mRNA abundance of c-mesenchymal-epithelial transition factor (c-Met), jejunal epidermal growth factor receptor (EGFR), and transforming growth factor-beta 1 (TGF-β1) in the jejunum and ileum of birds after subclinical NE challenge. In conclusion, 600 mg/kg of TA may be a promising tool to prevent and control subclinical NE by increasing intestinal antioxidant status in broilers.

Non-starch polysaccharide-degrading enzymes may improve performance when included in wheat- but not maize-based diets fed to broiler chickens under subclinical necrotic enteritis challenge.

The present study investigated whether supplementing fibre-degrading enzymes can ameliorate the severity of subclinical necrotic enteritis (NE) in broiler chickens offered wheat- or maize-based diets. A total of 1,544 mixed-sex broiler chickens were assigned to 16 experimental treatments as a 2 × 2 × 4 factorial arrangement of treatments. The factors were the following: NE challenge, yes or no; diet type, wheat- or maize-based; and enzyme supplementation, control (no enzyme), family 10 xylanase (XYN10), family 11 xylanase (XYN11) or β-mannanase (MAN). Each treatment was replicated 6 times, with 16 birds per replicate pen. A three-way challenge × diet type × enzyme interaction occurred for body weight at 21 d of age (P = 0.025) and overall feed conversion ratio (P = 0.001). In the non-challenged birds fed the wheat-based diet, supplementing MAN increased d 21 body weight compared to the control. In challenged birds fed the maize-based diet, supplemental XYN11 impeded body weight and overall FCR compared to the control. Birds offered the maize-based diet presented heavier relative gizzard weights at both 16 and 21 d of age (P < 0.001) and reduced liveability (P = 0.046) compared to those fed the wheat-based diet. Enzyme supplementation reduced ileal and jejunal digesta viscosity at 16 d of age only in birds fed the wheat-based diet (P < 0.001). XYN11 increased ileal digesta viscosity in birds fed the maize-based diet, and MAN reduced it in birds fed the wheat-based diet at 21 d of age (P = 0.030). Supplementing XYN11 improved ileal soluble non-starch polysaccharides (NSP) digestibility in birds fed the wheat-based diet compared to non-supplemented birds (P < 0.001). Birds fed the wheat-based diet displayed a higher abundance of Bifidobacterium, Lactobacillus and Enterobacteriaceae and butyric acid in the caeca at 16 d of age compared to birds fed the maize-based diet (P < 0.05). In conclusion, supplemental XYN11 exacerbated the negative impact of NE on growth performance in birds fed the maize-based diet. Supplementing wheat-based diets with fibre-degrading enzymes ameliorates production losses induced by NE.

Supplementation of reduced protein diets with

Context Necrotic enteritis (NE) has been considered a major threat to broiler gut health and growth performance. Aims This study aimed at investigating the effects of l-arginine (Arg) or l-citrulline (Cit) supplementation on intestinal morphology, short-chain fatty acid (SCFA), microbiota count, gut permeability, and pH in broilers fed reduced-protein diets during subclinical NE challenge. Methods Ross 308 cockerels (n = 720) were randomly assigned to six experimental treatments with eight replicates of 15 birds per pen. The treatments were standard protein without NE challenge (SP−), or with NE challenge (SP+); reduced protein (two percentage points lower crude protein) without NE challenge (RP−), or with NE challenge (RP+); RP+ plus added Arg (103% of Ross 308 requirement, RPA+) and RPC+ where supplemental Arg in RPA+ was replaced with Cit. A 2 × 2 factorial arrangement was employed for the first four treatments. Factors were NE (− or +) and protein concentration (SP or RP). Treatments SP+, RP+, RPA+, and RPC+ were analysed by one-way ANOVA. Key results Necrotic enteritis × protein interactions were detected for serum fluorescein isothiocyanate dextran (FITC-d) level, C. perfringens (P &lt; 0.05) count in the caeca (P &lt; 0.01), and acetic acid (P &lt; 0.01) and total SCFA concentrations in the ileum on Day 16 (P &lt; 0.001). Feeding the RP diet reduced serum FITC-d concentration, number of C. perfringens in the caeca, and increased acetic acid and total SCFA concentrations in the ileum compared with the SP group only in birds challenged with NE. Birds in the RPC+ treatment had greater jejunal villus height (P &lt; 0.001), and lower caecal C. perfringens and Enterobacteriaceae count than did those in the SP+ treatment (P ≤ 0.001). Conclusions The results indicated a benefit to gut health of broilers during NE challenge when replacing crystalline Arg with Cit in RP diets. Implications In part, replacement of Arg by Cit in the RP diets is of great potential to increase gut health, reduce growth loss, thus, minimising negative effects of NE in broilers.

Supplementation of reduced protein diets with

Context The impact of necrotic enteritis (NE) on acute-phase proteins, interleukins, blood mineral profiles, and gene expression have not been well documented. Aims This study aimed to determine the effects of l-arginine (Arg) or l-citrulline (Cit) supplementation on serum immunological parameters, serum mineral composition and gene expression in broilers fed reduced-protein diets (RP) during subclinical NE challenge. Methods Ross 308 cockerels (n = 720) were randomly assigned to six experimental treatments, with eight replicates of 15 birds per pen. The treatments were standard protein without and with NE challenge (SP−, SP+); reduced protein (2% points lower crude protein) without and with NE challenge (RP−, RP+), RP plus added Arg (103% of Ross 308 requirement) with NE challenge (RPA+) and RPC+ where supplemental Arg in RPA+ was replaced with Cit. A 2 × 2 factorial arrangement was employed for the first four treatments. Additionally, treatments SP+, RP+, RPA+, and RPC+ were analysed by one-way ANOVA. Key results The NE × protein interactions indicated that serum calcium concentration decreased in birds fed the RP diets only when challenged with NE (P &lt; 0.05). The NE × protein interactions showed that the NE challenge downregulated the mRNA expression of jejunal y+ L amino acid transporter-2, and mucin 2 only in birds fed the RP diets (P &lt; 0.05). Feeding the RP decreased expression of catenin alpha 1, but increased expression of claudin 5 and tight junction protein genes compared with the SP (P &lt; 0.05). Birds in the RPC+ treatment had increased gene expression of tight junction protein and claudin 5 compared with the SP+ treatment (P &lt; 0.05). Conclusions Dietary protein level and infection with NE both have an impact on immune response and expression of genes involved in immunity and nutrient digestibility. In part replacement of Arg with Cit in the RPC diet may have beneficial effects on gene expression in NE-challenged birds. Implications Feeding RP diets may alleviate a decline in growth during subclinical NE by increasing gene expression of tight junction proteins compared with the SP diets.

Supplementation of reduced protein diets with

Context Improving immune status through nutritional adjustments may be part of an effective strategy to reduce reliance on antibiotic growth promoters for controlling necrotic enteritis (NE) in broiler chickens. Aims This study examined the effect of dietary protein level and the replacement of crystalline l-arginine (Arg) with l-citrulline (Cit) in the reduced-protein diet on the performance of broilers challenged with subclinical NE. Methods Ross 308 cockerels (n = 720) were randomly allocated to six dietary treatments, with eight replicates of 15 birds per pen, during a 35-day feeding experiment. The treatments were as follows: standard protein without NE challenge (SP−); standard protein with NE challenge (SP+); reduced protein (two percentage points lower crude protein) without NE challenge (RP−); reduced protein with NE challenge (RP+); RP+ plus added Arg (103% of RP, RPA+) and RPC+ where supplemental Arg in RPA+ was replaced with Cit. The first four treatments were considered as a 2 × 2 factorial arrangement, with factors being NE (− or +) and protein level (SP or RP). Treatments SP+, RP+, RPA+, and RPC+ were analysed by one-way ANOVA. Key results Subclinical NE challenge reduced feed intake (FI), reduced body weight gain (BWG) and increased feed to gain ratio (FCR) from Day 0 to Day 35, increased intestinal lesion scores on Day 16, and reduced relative breast yield on Day 35 (P &lt; 0.05). Feeding RP diets increased FI (P &lt; 0.001), increased BWG (P &lt; 0.01) and reduced FCR (P &lt; 0.01) during the grower phase compared with SP diets when birds were challenged with NE. Birds in the RPC+ treatment had a lower overall FCR than did those in the SP+ treatment (P &lt; 0.001). Birds in the RPA+ treatment had similar FI, BWG and FCR to those in the RP+ treatment (P &gt; 0.05). Conclusions Collectively, the results showed protective effects of replacing the supplemental Arg with Cit against NE in RP diets, as indicated by higher performance during and after the challenge. Implications Feeding the RP diets supplemented with Cit may be part of an effective strategy to reduce reliance on antibiotic growth promoters for controlling NE in broiler chickens.

Probiotics Bacillus licheniformis Improves Intestinal Health of Subclinical Necrotic Enteritis-Challenged Broilers.

Necrotic enteritis infection poses a serious threat to poultry production, and there is an urgent need for searching effective antibiotic alternatives to control it with the global ban on in-feed antibiotics. This study was conducted to investigate the effects of dietary Bacillus licheniformis replacing enramycin on the growth performance and intestinal health of subclinical necrotic enteritis (SNE)-challenged broilers. In total, 504 1-day-old Arbor Acres male chickens were selected and subsequently assigned into three treatments, including PC (basal diet + SNE challenge), PA (basal diet extra 10 mg/kg enramycin + SNE challenge), and PG (basal diet extra 3.20 × 109 and 1.60 × 109 CFU B. licheniformis per kg diet during 1–21 days and 22–42 days, respectively + SNE challenge). Results showed that B. licheniformis significantly decreased the intestinal lesion scores and down-regulated the Claudin-3 mRNA levels in jejunum of SNE-infected broilers on day 25, but increased the mucin-2 gene expression in broilers on day 42. In addition, B. licheniformis significantly up-regulated the mRNA levels of TRIF and NF-κB of SNE-challenged broilers compared with the control group on day 25 and TLR-4, TRIF compared with the control and the antibiotic group on day 42. The mRNA expression of growth factors (GLP-2 and TGF-β2) and HSPs (HSP60, HSP70, and HSP90) were up-regulated in B. licheniformis supplementary group on days 25 and 42 compared with group PC. LEfSe analysis showed that the relative abundance of Lachnospiraceae_UCG_010 was enriched in the PG group; nevertheless, Clostridiales_vadinBB60 and Rnminococcaceae_NK4A214 were in PA. PICRUSt analysis found that the metabolism of cofactors and vitamins, amino acid metabolism, and carbohydrate metabolism pathways were enriched, whereas energy metabolism, membrane transport, cell motility, and lipid metabolism were suppressed in B. licheniformis-supplemented groups as compared with the PC control. In conclusion, dietary supplementation of B. licheniformis alleviated the intestinal damage caused by SNE challenge that coincided with modulating intestinal microflora structure and barrier function as well as regulating intestinal mucosal immune responses.

Effect of Probiotics and Multi-Component Feed Additives on Microbiota, Gut Barrier and Immune Responses in Broiler Chickens During Subclinical Necrotic Enteritis.

The withdrawal of antibiotic growth promoters from poultry feed has increased the risk of necrotic enteritis (NE) outbreaks. This study examined the effects of a probiotic (PROB) or probiotic/prebiotic/essential oil supplement (PPEO) during a subclinical NE challenge. On day (d) of hatch, 960 male broilers were randomized to four groups (8 pens/treatment, 30 birds/pen) including (1) negative control (NC): corn-soybean meal diet; (2) positive control (PC): NC + 20 g Virginiamycin/ton diet; (3) NC + 227 g PROB/ton diet; and (4) NC + 453 g PPEO/ton diet. One d after placement, birds were challenged by a coccidia vaccine to induce NE. Feed intake and body weights were measured on d 8 (NE onset) and end of each feeding period. On d 8, the small intestines of three birds/pen were examined for NE lesions. Jejunum samples and ileal mucosal scrapings from one bird/pen were respectively collected to measure mRNA abundance (d 8 and d 14) and profile the microbiota (d 8 and d 42). Data were analyzed in JMP or QIIME 2 and significance between treatments identified by LSD (P < 0.05). PROB and PPEO had significantly lower mortality (d 0–14) and NE lesion scores compared to NC. Feed conversion ratio was significantly lower in PC, PROB, and PPEO, while average daily gain was higher in PPEO and PC groups compared to NC from d 0–42. On d 8 and d 14, mRNA abundance of claudin-3 was higher in PPEO compared to NC. On d 14, compared to NC, mRNA abundance of sIgA and PGC-1α in PROB and PPEO were lower and higher, respectively. Compared to NC, PPEO increased mTOR abundance on d 14. On d 8, relative abundance of Clostridium sensu stricto 1, Ruminiclostridium9, Prevotellaceae, Prevotellaceae UCG-014, ASF356, and Muribaculaceae was higher in NC compared to PPEO and PROB, while Lactobacillus was lower in NC. Escherichia-Shigella had higher abundance in PC compared to PPEO and PROB. Collectively, these data indicate that during a subclinical naturally occurring NE, supplementation of PROB or PPEO supports performance and reduces intestinal lesions, potentially through modifying tight junction proteins, gut microbiota, immune responses, and cell metabolism.

Dietary hydrolysed yeast cell wall extract is comparable to antibiotics in the control of subclinical necrotic enteritis in broiler chickens

ABSTRACT 1. The aim of this study was to examine the effect of yeast cell wall (YCW) on performance and physiological responses of broiler chickens under subclinical necrotic enteritis challenge. 2. Six treatments in a 2 × 3 factorial arrangement (non-challenged or challenged plus no supplement, YCW or antibiotics (AB)) was used. Each treatment was replicated eight times with 12 birds per replicate. The treatments included: (1) Positive control (PC; no additive, not challenged); (2) Negative control (NC; no additive, with challenge); (3) YCWN = yeast cell wall (2.0 g/kg diet, not challenged; (4) YCWC = yeast cell wall (2.0 g/kg diet, challenged); (5) ABN = zinc bacitracin 50 ppm + Salinomycin 60 ppm, not challenged); (6) ABC = zinc bacitracin 50 ppm + Salinomycin 60 ppm, challenged). 3. Eimeria challenge at 9 d of age did not affect feed intake (FI), body weight gain (BWG), FCR or liveability at 10 d. The BWG and FCR at 10 d were greater (P < 0.05) in birds fed YCW or AB (AB) diets relative to the PC or NC groups. On 24 and 35 d, FI, BWG, FCR and flock uniformity (28 d) were greater (P < 0.05) in the challenged groups fed YCW or AB diets compared to NC group. 4. Supplementation with YCW ameliorated the negative effects of NE on liver, spleen and bursa weight of birds. 5. Necrotic enteritis challenge decreased (P < 0.05) caecal Lactobacillus and Bifidobacterium spp. counts, and increased ileum lesion score and caecal Clostridium perfirngens counts. This was reversed by the addition of either YCW or AB. 6. Supplementation with YCW and AB resulted to a greater (P < 0.05) dressing percentage and meat yield (35 d). 7. The results indicated that YCW plays a vital role in improving the physiological response and performance of broiler chickens under subclinical necrotic enteritis challenge.

Intermittent lighting improves resilience of broilers during the peak phase of sub-clinical necrotic enteritis infection

Necrotic enteritis, either in its clinical or sub-clinical form is known to cause massive economic losses in the broiler chicken industry. Currently, the use of in-feed antibiotics as growth promoters is discouraged. Therefore, mechanisms to control NE through diet include reduction of digesta viscosity, promotion of lower pH in the gastrointestinal tract (GIT) through acidification of feed, production of short-chain fatty acids and overall stimulation of beneficial bacteria growth. Intermittent lighting programs increase feed retention in the crop and reduce pH in the foregut compartments in comparison with standard commercial lighting programs and therefore may be a valuable, yet underexploited, barrier to prevent the invasion of the GIT by pathogens. In this experiment, a 2 × 2 factorial arrangement of treatments was employed in a randomized design to investigate whether intermittent lighting would increase broiler resilience to sub-clinical necrotic enteritis. A total of 390 Cobb 500 same-hatch, mixed sex, day-old chicks were assigned to 30 floor pens to test the effect of 2 factors, namely, lighting schedule (continuous, 18L:6D vs. intermittent, 1L:3D:1L:3D:1L:3D:1L:3D:2L:6D) and a sub-clinical necrotic enteritis challenge (challenge vs. no challenge). Challenged birds had lower feed intake and weight gain and poorer feed conversion ratio (FCR; P < 0.005). Intermittent lighting reduced feed intake (P < 0.05) without compromising final body weight gain. During the peak phase of Clostridium perfringens Type A infection, the negative impact of the disease challenge on feed efficiency was lower for animals under intermittent lighting than for those under a 18L:6D schedule (2-way interaction, P < 0.005). Thus, in flocks that are raised under antibiotic-free production systems, intermittent lighting programs applied at least during the critical period for necrotic enteritis risks, i.e., d 18–24, may be a practical, non-medicated way to increase resilience of broilers to this disease.

Reintroduction of microflora from necrotic enteritis-resistant chickens reduces gross lesions and improves performance of necrotic enteritis-challenged broilers

SUMMARY Probiotics feature one or multiple strains of viable bacteria that beneficially modulate the intestinal health of the host. The key criteria for probiotics, like all feed additives, are that they must be safe and efficacious to use. One of the efficacious measures for probiotics used in poultry feed is their ability to act as an alternative to in-feed antibiotics against economically significant diseases like necrotic enteritis (NE). The current study investigated the effect of the reintroduction of crude ileal and cecal contents from previously NE-challenged chickens on performance, mortality, and intestinal lesions of young broilers under NE challenge. As expected, a subclinical NE challenge depressed bird performance (P

The role of supplemental glycine in establishing a subclinical necrotic enteritis challenge model in broiler chickens

Subclinical necrotic enteritis (NE) is an economically important disease in the broiler industry. With the move towards removal of antibiotics from feeds, solutions to control subclinical NE are desperately being sought. Dietary glycine has been shown to promote proliferation of Clostridium perfringens (Cp) and may thus be useful to include in a NE challenge model. A study was conducted to evaluate the effect of increased dietary glycine levels on subclinical NE. A 2 × 2 × 2 factorial arrangement of treatments was carried out using day-old male Ross 308 chicks (n = 624) allocated to 48 floor pens with 8 treatments of 6 replicates with 11 birds per treatment. Factors were: Cp challenge (C− or C+), Eimeria spp. challenge (E− or E+), and dietary glycine in the grower diet (0 or 10 g/kg). Birds had higher FCR when challenged with Eimeria (P < 0.01) or Cp (P < 0.05) on d 24 or Cp on d 35 but FCR was lower when fed glycine on d 24 (P < 0.01). Supplementation of glycine reduced feed intake on d 24 and increased weight gain on d 35 (P < 0.05). A Cp × Eimeria × glycine interaction (P < 0.05) showed a higher jejunal lesion scores in birds challenged with a combination of Cp and glycine compared with those with Eimeria and glycine or the unchallenged birds. Lesion score interactions between Cp and glycine (P < 0.05) in the ileum and Cp and Eimeria in the duodenum (P < 0.05) and ileum (P < 0.05) illustrated higher lesion scores in birds challenged with Cp without Eimeria or glycine compared to those not challenged with Cp. This study suggests that using glycine can partially replace Eimeria in a subclinical NE challenge model in promoting the intestinal lesions but not impairing chicken performance.

An early feeding regime and a high-density amino acid diet on growth performance of broilers under subclinical necrotic enteritis challenge.

Broilers that have early access to feed have been shown to have enhanced immune system and gut development and heightened resilience against necrotic enteritis (NE). This study examined the effect of early feeding a high amino acid density diet on performance of broilers under a sub-clinical NE challenge model. Ross 308 broilers (n = 576) were assigned to a 2 × 2 × 2 factorial design with 2 feeding regimes (feed access either within 6 h post-hatch or after 48 h post-hatch), 2 diets (control diet or the control diet with an additional 10% digestible amino acids [HAA]) and either presence or absence of NE challenge. Oral administrations of Eimeria species (d 9) and a field strain of Clostridium perfringens (d 14) were used to induce NE. Broiler performance was analysed at d 13, 23, 30 and 35. Intestinal lesion score and bacterial count were analysed on d 16. The NE challenge reduced overall bird performance and induced severe intestinal lesions, without causing notable mortality. At d 23 bird weight was significantly lower (P < 0.001) in the challenged birds compared with the unchallenged birds, but by d 30 the challenged birds had recovered and challenge no longer had an impact on bird performance. Birds fed the HAA diet had greater body weight by d 35 and heightened Lactobacillus content in the ileum at d 16 (P < 0.05). Birds that were fed the HAA diet after a period of fasting performed better in terms of feed conversion ratio (FCR) under challenge. The findings from this study suggest there are beneficial effects of feeding high amino acid diets to birds in response to external stresses, such as post-hatch fasting and subclinical NE.