Effects of dietary protein source and level on intestinal populations of Clostridium perfringens in broiler chickens

Phase-specific outcmes of arginine or branched-chain amino acids supplementation in low crude protein diets on performance, nutrient digestibility, and expression of tissue protein synthesis and degradation in broiler chickens infected with mixed Eimeria spp

A 35-d study investigated the impact of dietary supplementation with Arginine (Arg) or branched-chain amino acids (BCAA) of broilers receiving low-protein diets whilst infected with mixed Eimeria species. All birds were given the same starter (d0-10) and finisher (d28-35) diets. The 4 grower diets used were a positive control (PC) with adequate protein (18.5%), a low protein diet (NC;16.5% CP), or the NC supplemented with Arg or BCAA. Supplemental AA was added at 50% above the recommended levels. The treatments were in a 4 × 2 factorial arrangement, with 4 diets, with or without Eimeria inoculation on d14. Birds and feed were weighed after inoculation in phases: prepatent (d14-17), acute (d18-21), recovery (d22-28), and compensatory (d29-35). Ileal digesta, jejunum, and breast tissue were collected on d21, 28, and 35. There was no diet × Eimeria inoculation on growth performance at any phase. Infected birds weighed less and consumed less feed (P < 0.05) in all phases. In the prepatent and acute phases, birds on the Arg diets had higher weight gain (P < 0.05) and lower FCR, similar to PC, when compared to NC and BCAA-fed ones. Infection reduced AA digestibility on d21 and 28 (Met and Cys). However, birds that received supplemental AA had higher digestibility (P < 0.05) of their respective supplemented AA on d 21 only. Infected birds had lower (P < 0.05) BO + AT and higher PEPT1 expression on d21. There was a diet × Eimeria interaction (P = 0.004) on gene expression at d28; 4EBP1 genes were significantly downwardly expressed (P < 0.05) in birds fed Arg diet, irrespective of infection. Infected birds exhibited an upward expression (P < 0.05) of Eef2 on d21 and d28 but experienced a downward expression on d35. Supplemental Arg and BCAA had variable effects on growth performance, apparent ileal AA digestibility, and genes of protein synthesis and degradation, but the effect of Arg on promoting weight gain, irrespective of the Eimeria challenge, was more consistent.

Necrotic enteritis and antibiotic-free production of broiler chickens: Challenges in testing and using alternative products

The global trend towards raising broiler chickens without the use of in-feed antibiotics (IFAs) means that there is an ongoing need to develop alternative treatments capable of delivering the benefits that IFAs previously provided. IFAs supported the productivity performance of chickens and played a key role in maintaining their health. Necrotic enteritis (NE) is an important disease of broilers that affects health, productivity, and welfare, and was previously well controlled by IFAs. However, with the reduction in IFA use, NE is resurgent in some countries. Vaccines and various feed additives, including pre-, pro-, and postbiotics, phytobiotics, fatty acids, and phage therapies have been introduced as alternative methods of NE control. While some of these feed additives have specific activity against the NE pathogen, Clostridium perfringens, most have the more general goal of reinforcing gut health. Extensive reviews of the effects of many of these feed additives on gut health have been published recently. Hence, rather than cover previously well reviewed areas of research this review focuses on the challenges and pitfalls in undertaking experimental assessment of alternative NE treatments and translating laboratory research to real world commercial production settings. The review is based on the author's particular experience, reading, thoughts, and analysis of the available information and inevitably presents a particular understanding that is likely to be at odds with others thinking on these issues. It is put forward to stimulate thinking and discussion on the issues covered.

Modulation of Broiler Intestinal Changes Induced by Clostridium perfringens and Deoxynivalenol through Probiotic, Paraprobiotic, and Postbiotic Supplementation

Deoxynivalenol (DON) is a predisposing factor for necrotic enteritis. This study aimed to investigate the effects of a DON and Clostridium perfringens (CP) challenge on the intestinal morphology, morphometry, oxidative stress, and immune response of broilers. Additionally, we evaluated the potential of a Lactobacillus spp. mixture as an approach to mitigate the damage induced by the challenge. One-day-old broiler chickens (n = 252) were divided into seven treatment groups: Control, DON, CP, CP + DON, VL (DON + CP + viable Lactobacillus spp. mixture), HIL (DON + CP + heat-inactivated Lactobacillus spp. mixture), and LCS (DON + CP + Lactobacillus spp. mixture culture supernatant). Macroscopic evaluation of the intestines revealed that the CP + DON group exhibited the highest lesion score, while the VL and HIL groups showed the lowest scores. Microscopically, all Lactobacillus spp. treatments mitigated the morphological changes induced by the challenge. DON increased levels of reactive oxygen species (ROS) in the jejunum, and CP increased ROS levels in the jejunum and ileum. Notably, the Lactobacillus spp. treatments did not improve the antioxidant defense against CP-induced oxidative stress. In summary, a Lactobacillus spp. mixture, whether used as a probiotic, paraprobiotic, or postbiotic, exerted a partially protective effect in mitigating most of the intestinal damage induced by DON and CP challenges.

Early Salmonella Typhimurium inoculation may obscure anti-interleukin-10 protective effects on broiler performance during coccidiosis and necrotic enteritis challenge

Anti-interleukin (IL)-10 may preserve broiler performance during coccidiosis by diminishing Eimeria spp. host-evasion but has not been evaluated during secondary Clostridium perfringens challenge (necrotic enteritis). Early Salmonella Typhimurium inoculation is implemented in some models to improve repeatability-a potential confounder due to Salmonella using similar IL-10 host evasion pathways. The objective was to evaluate performance and disease outcomes in broilers fed anti-IL-10 during necrotic enteritis challenge ± S. Typhimurium. Three 42 d replicate studies in wire-floor cages (32 cages/replicate) were conducted with Ross 308 chicks assigned to diets ± 0.03% anti-IL-10 for 25 d before moving to floor pens for the study remainder. In replicates 1 and 2, 640 chicks were placed at hatch (20/cage) and inoculated with sterile saline ± 1 × 108 colony forming units (CFU) S. Typhimurium. Replicate 3 placed 480 chicks (15/cage) at hatch. On d 14, S. Typhimurium-inoculated chicks (replicates 1 and 2) or those designated for challenge (replicate 3) were inoculated with 15,000 sporulated Eimeria maxima M6 oocysts. On d 18 and 19, half the E. maxima-challenged chicks were gavaged with 1 × 108 CFU C. perfringens. Body weight (BW) and feed intake were measured throughout, while 6 chicks/ treatment were scored for jejunal lesions at 7 and 3 d postinoculation (pi) with E. maxima and C. perfringens, respectively. Oocyst shedding was measured at 8 and 4 dpi with E. maxima and C. perfringens, respectively. Performance and oocyst shedding were analyzed with diet and challenge fixed effects (SAS 9.4), whereas lesion scores and mortalities were analyzed by ordinal logistic regression (R 4.2.2; P ≤ 0.05). In replicate 3, no wk 3 feed conversion ratio (FCR) differences were observed between chicks fed anti-IL-10 challenged with E. maxima ± C. perfringens, whereas control-fed chicks had a 50 point less efficient FCR during E. maxima + C. perfringens challenge vs. E. maxima only (P = 0.04). Outcomes suggest anti-IL-10 may preserve bird feed efficiency during necrotic enteritis challenge in models without S. Typhimurium.

Evaluating a Salmonella Typhimurium, Eimeria maxima, and Clostridium perfringens coinfection necrotic enteritis model in broiler chickens: repeatability, dosing, and immune outcomes

Coccidiosis and necrotic enteritis negatively impact poultry production, making challenge model repeatability important for evaluating mitigation strategies. Study objectives were: 1) evaluate Salmonella Typhimurium-Eimeria maxima-Clostridium perfringens necrotic enteritis coinfection model repeatability and 2) investigate E. maxima dose and early S. Typhimurium challenge on immune responses. Three trials using Ross 308 chicks assigned to 12 cages/trial (7 chicks/cage) in wire-floor brooders were completed. Trials 1 and 2 determined E. maxima dose for necrotic enteritis challenge in trial 3. Chicks in trials 1 and 2 were inoculated with 0 (control), 5, 15, or 25,000 sporulated E. maxima M6 oocysts on d 14 and jejunal lesion scores evaluated on d 20. In trial 3, chicks were assigned to control or necrotic enteritis challenge (42 chicks/group). Necrotic enteritis challenge chicks were inoculated with 1 × 105 colony forming units (CFU) S. Typhimurium on d 1, 15,000 E. maxima oocysts on d 14, and 1 × 108 CFU C. perfringens on d 19 and 20 with lesion scoring on d 22. Bird and feeder weights were recorded throughout each trial. Peripheral blood mononuclear cells (PBMC) were isolated from 1 chick/cage at baseline (all trials), 4 chicks/dose (trials 1 and 2) or 8 chicks/challenge (trial 3) 24 h post-inoculation (pi) with E. maxima for immunometabolic assays and immune cell profiling. Data were analyzed by mixed procedure (SAS 9.4) with challenge and timepoint fixed effects (P ≤ 0.05, trends 0.05 ≤ P ≤ 0.01). Inoculating chicks with 15,000 E. maxima oocysts increased d 14 to 20 FCR 79 points (trials 1 and 2; P = 0.009) vs. unchallenged chicks and achieved a target lesion score of 2. While C. perfringens challenge reduced trial 3 performance, average lesion scores were <1. Salmonella inoculation on d 1 tended to increase PBMC ATP production 41.6% 24 hpi with E. maxima vs. chicks challenged with E. maxima only (P = 0.06). These results provide insight for future model optimization and considerations regarding S. Typhimurium's effect on E. maxima immune response timelines.

Fish and Black Soldier Fly Meals as Partial Replacements for Soybean Meal Can Affect Sustainability of Productive Performance, Blood Constituents, Gut Microbiota, and Nutrient Excretion of Broiler Chickens

One hundred and twenty, one-day-old male broiler chicks were used to investigate the effects of supplementation with different dietary protein sources on their performance and immune systems. Chicks were randomly divided into four equal experimental groups (six replicates, each of five chicks). The first group served as a control and was fed a standard corn-soybean meal diet. The second, third, and fourth groups were fed diets in which the soybean meal (SBM) was partly replaced by fish meal (FM), black soldier fly larvae (BSFL), and black soldier fly prepupae (BSFP), respectively. Throughout 1-14 and 15-42 days of age, FM, BSFL, and BSFP were added at 3 and 5%, respectively. The feed conversion ratio (FCR) of the FM group was the best among the tested groups. Feeding BSFP decreased final body weight (BW), BW gain, feed intake, and impaired the FCR compared to the other treatments for the entire experimental period. The BSFP group had significantly lower cecal Salmonella counts compared to the control group and lower total bacterial counts compared to the other groups except for BSFL. BSFL can be fed to broiler chickens at 3% during the starter period and 5% during the grower-finisher periods without negative influences on growth performance, red blood cell characteristics, blood lipid profiles, and nutrient excretion, while BSFP can improve the chickens' gut ecosystem.

Integrative analysis of transcriptome and metabolome reveals probiotic effects on cecal metabolism in broilers

BACKGROUND

Probiotics play an important role in the host and have attracted widespread attention as an alternative to antibiotics. Arbor Acres broilers were used in the present experiment and fed different doses of compound probiotics at 1, 5, and 10 g kg^-1 . The effects of compound probiotics on broiler growth performance and cecal transcriptome and metabolome were investigated.

RESULTS

We discovered 425 differentially expressed genes (DEGs; upregulated: 256; downregulated: 169) in the cecal transcriptome study. These DEGs were assigned to fat metabolic pathways, such as the peroxisome proliferator-activated receptor (PPAR) signaling pathway, according to KEGG analysis. Probiotics downregulated LPL and upregulated PPARα expression in the cecum. In metabolome analysis of the cecum of cecum, we screened 86 differential metabolites and performed KEGG enrichment analysis of these metabolites. The KEGG analysis showed that these differentially expressed metabolites were annotated to nucleotide metabolism-related pathways, such as purine metabolism. In the cecum, probiotics upregulated the content of guanine, AMP, 3'-AMP, adenylosuccinate, deoxyguanosine, and ADP-ribose, whereas they downregulated the content of 5-hydroxyisourate. Comprehensive transcriptome and metabolome analysis revealed that glycolysis, gluconeogenesis, and glycerophospholipid metabolism pathways were jointly enriched in cecum of broilers fed a probiotic-containing diet.

CONCLUSION

This study provides valuable information for studying the regulation and gene metabolism network of probiotics on cecal metabolism in broilers. © 2022 Society of Chemical Industry.

Selective nourishing of gut microbiota with amino acids: A novel prebiotic approach?

Prebiotics are dietary substrates which promote host health when utilized by desirable intestinal bacteria. The most commonly used prebiotics are non-digestible oligosaccharides but the prebiotic properties of other types of nutrients such as polyphenols are emerging. Here, we review recent evidence showing that amino acids (AA) could function as a novel class of prebiotics based on: (i) the modulation of gut microbiota composition, (ii) the use by selective intestinal bacteria and the transformation into bioactive metabolites and (iii) the positive impact on host health. The capacity of intestinal bacteria to metabolize individual AA is species or strain specific and this property is an opportunity to favor the growth of beneficial bacteria while constraining the development of pathogens. In addition, the chemical diversity of AA leads to the production of multiple bacterial metabolites with broad biological activities that could mediate their prebiotic properties. In this context, we introduce the concept of "Aminobiotics," which refers to the functional role of some AA as prebiotics. We also present studies that revealed synergistic effects of the co-administration of AA with probiotic bacteria, indicating that AA can be used to design novel symbiotics. Finally, we discuss the difficulty to bring free AA to the distal gut microbiota and we propose potential solutions such as the use of delivery systems including encapsulation to bypass absorption in the small intestine. Future studies will need to further identify individual AA, dose and mode of administration to optimize prebiotic effects for the benefit of human and animal health.

Amino Acids Supplementation Affects Sustainability of Productive and Meat Quality, Survivability and Nitrogen Pollution of Broiler Chickens during the Early Life

The response to amino acid (AAs) supplementation on broiler production, carcass and meat traits and nitrogen in the excreta during the early growth period was evaluated. Two experiments were performed during 1-28 d (245 birds, experiment 1) and 1-21 d of age (455 birds, experiment 2). In both experiments, the positive control (PC) diet had 22.5% crude protein (CP) and the negative control group (NC) diet had around 18% CP with the same methionine (Met) plus lysine (Lys) concentration as the PC diet. In experiment 1, the NC diet was fed to the other five groups supplemented with synthetic amino acids, such as L-arginine (Arg), L-threonine (Thr), L-valine (Val), L-isoleucine (Ile) or all these AAs, respectively. In experiment 2, the NC diet was formulated to contain 18% CP with either corn-soybean meal and animal protein or with only vegetable protein. Both NC diets were offered to the other ten groups with synthetic amino acids such as L-Arg, L-Thr, L-Val, L-tryptophan (Trp) or a combination of all these AAs plus L-isoleucine (Ile), respectively. In conclusion, broilers fed 18% CP supplemented with DL-Met plus L-Lys showed lower performance and a European production efficiency value (EPEV); Arg, Thr and Val addition improved growth, the feed conversion ratio and EPEV of the diets containing animal protein only, but broiler performance and EPEV was lower than with PC, indicating that DL-Met, L-Lys, L-Arg, L-Thr and L-Val supplementation may be limited in low-protein diets. Furthermore, a low-protein diet supplemented with amino acids did not affect the survivability of broilers up to 28 days of age.

Complete replacement of soybean meal with black soldier fly larvae meal in feeding program for broiler chickens from placement through to 49 days of age reduced growth performance and altered organs morphology

Black soldier fly larvae meal (BSFLM) is characterized with good nutritional and functional attributes. However, there is limited data on inclusion of BSFLM in broiler chicken rations from placement through to market weight. Therefore, we examined growth and organ responses of partial to complete replacement of soybean meal (SBM) with BSFLM in a practical feeding program. A total of 1,152 d-old male Ross × Ross 708 chicks were allocated to 48 pens and assigned one of six diets (n = 8). The diets were: a basal corn-SBM diet (0%BSFLM), 4 diets in which SBM in 0%BSFLM was replaced with BSFLM at 12.5, 25, 50, and 100% and a final diet (0 + AGP) in which 0%BSFLM was treated with coccidiostat (70 mg Narasin/kg) and antibiotic (55 mg Bacitracin Methylene Disalicylate/kg). For energy fortification, soy oil was used for 0%BSFLM diets and black soldier fly oil in the other diets. Body weight, feed intake (FI), BW gain (BWG), and mortality-corrected feed conversion ratio (FCR) were reported. Organ weights were recorded on d 24 and 49. On d 10, birds fed diets 12.5, 25, and 0 + AGP had higher BWG than birds fed diets 0, 50, and 100 (P < 0.01), and birds fed diet 100 had lower BWG than birds fed diets 0 or 50 (P < 0.01). Birds fed diets 50 and 100 had lower BWG than birds fed all other diets on d 24 and 49 (P < 0.05). Overall (d 0-49), BSFLM linearly (P < 0.01) decreased BW, BWG, and FI and increased FCR and mortality. The overall BWG of 50 and 100% BSFLM birds was 92 and 81% of birds fed 0%BSFLM, repectively and coresponding overall FI was 96 and 90%. An increase in gizzard, small intestine, pancreas, and liver relative weights were observed with increasing BSFLM inclusion (P < 0.01). The data indicated that lower levels of BSFLM could provide some growth-promoting effects commensurate to antibiotics in the starter phase. However, replacing SBM with greater amounts (≥50) of BSFLM reduced growth and increased organ size.

Over-toasting dehulled rapeseed meal and soybean meal, but not sunflower seed meal, increases prececal nitrogen and amino acid digesta flows in broilers

Poorly digestible proteins may lead to increased protein fermentation in the ceca of broilers and hence, the production of potentially harmful metabolites. To evaluate effects of protein fermentation on gut health, an experimental contrast in ileal nitrogen (N) and amino acid (AA) flow is required. Therefore, our objective was to develop a model that creates a contrast in protein fermentation by increasing the prececal flow of protein within ingredients. To this end, we used additional toasting of protein sources and evaluated the effect on prececal N and AA flows. One-day-old Ross 308 male broilers (n = 480) were divided over 6 dietary treatments, with 8 replicate pens with 10 broilers each. Diets contained 20% of a regular soybean meal (SBM), high protein sunflower seed meal (SFM) or a dehulled rapeseed meal (dRSM) as is, or heat damaged by secondary toasting at 136°C for 20 min (tSBM, tSFM, or tdRSM). Ileal and total tract digesta flows of N and AA were determined with 5 birds per pen in their third week of life using an inert marker (TiO2) in the feed. Additional toasting increased the feed conversion ratio (FCR) only in birds fed dRSM (1.39 vs. 1.31), but not SBM and SFM (interaction P = 0.047). In SBM, additional toasting increased the flow of histidine, lysine, and aspartate through the distal ileum and excreted, while in SFM it had no effect on flows of N and AA. Toasting dRSM increased the prececal flows and excretion of N (862 vs 665 and 999 vs 761 mg/d, respectively) and of the AA. Of the ingredients tested, toasting dRSM is a suitable model to increase protein flows into the hind-gut, permitting the assessment of effects of protein fermentation.

Comparative Efficacy of Postbiotic, Probiotic, and Antibiotic Against Necrotic Enteritis in Broiler Chickens

Prevention of necrotic enteritis (NE), caused by Clostridium perfringens (C. perfringens), is one of the most important goals to improve the profitability of broiler chickens. This work aimed to compare the efficacy of 2 antibiotic alternatives including a postbiotic (dry feed additive and aqueous nonviable Lactobacillus (L.) species fermentation) and a probiotic (dry feed additive and aqueous Bacillus (B.) subtilis and B. lischeniformis mixture) with an antibiotic (amoxicillin in water) against NE. Four hundred, day-old broiler chicks were divided into 8 equal groups (Gs), n = 50 each (5 replicates; 10 each). Chickens of G1 (postbiotic dry-feed additive), G2 (postbiotic and antibiotic in drinking water), G3 (postbiotic dry and aqueous), G4 (probiotic dry-feed additive), G5 (probiotic and antibiotic in drinking water), G6 (probiotic dry and aqueous), and G7 (nontreated) were orally inoculated with a toxigenic C. perfringens type A on the d 19 to 21 of age and predisposed with 3X coccidial vaccine for induction of NE. However, chickens of G8 were kept nontreated or challenged. The severity of NE signs was markedly decreased in G3 in comparison with other challenged treatment groups, and the mortality rates were 22%, 10%, 16%, 22%, 12%, 20%, and 36% in Gs 1, 2, 3, 4, 5, 6, and 7, respectively. The best significant (P ≤ 0.05) feed conversion ratio was detected in G3 (1.51), G6 (1.54), and G2 and G8 (1.61). In addition, the European production efficiency factor was significantly (P ≤ 0.05) improved in G3 (279.33) and G2 (266.67), but it was decreased in G7 (177.33) when compared with G8 (339.33). An improvement in intestinal and hepatic pathology and liver function tests, as well as a significant (P ≤ 0.05) decrease in bacterial counts were observed in Gs 2, 5, 3, 6, 1, and 4, respectively in comparison with G7. Immunologically, the highest significant (P ≤ 0.05) hemagglutination inhibition antibody titers for Newcastle disease virus vaccine were in Gs 1 and 3 (6.4 log₂). In conclusion, the combined feed and water postbiotic treatment demonstrated promising results in ameliorating the severity of NE and improving the hepatic and the immune status of broiler chickens when compared with the commonly used probiotic and antibiotic.

Effect of dietary β-Mannanase addition on performance, pododermatitis, and intestinal morphology as well as digesta Clostridium perfringens in broiler chickens: a pilot study

This preliminary study was conducted to evaluate the effects of β-mannanase in diets of broilers on performance, pododermatitis, intestinal morphology, and digesta Clostridium perfringens counts. A total of 264 broilers (Ross 308) were randomly allotted to four treatments. A wheat-soybean based diet (CO) was supplemented with either 0.15 g xylanase/kg (XY), 0.15 g xylanase/kg + 110 mL β-mannanase/ton (MA1) or 0.15 g xylanase/kg + 220 mL β-mannanase/ton (MA2). At the end of the experiment, only significant differences in body weight were noted between groups fed MA1 and MA2 diets (2501 g vs 2641 g, respectively). Birds fed MA1 had significantly the lowest pododermatitis scores (2.26) compared to other groups. Ileal villus height measurements revealed that birds fed CO and MA2 diets had significantly higher values (1614 and 1651 µm, respectively) than those fed the MA1 diet (1489 µm). The positive percent of Clostridium perfringens in intestinal digesta at d 36 was significantly the highest in the XY group. Overall, although not improving performance, supplementing the diet with β-mannanase (110 mL/ton) contributed positively to foot pad health.

Precision intestinal nutrition: knowledge and gaps regarding the role of amino acids during an enteric challenge

Poultry nutritionists continually strive for more “precision” nutritional programs that provide the exact balance of nutrients that maximize broiler growth performance without economically and environmentally costly excesses. Many factors affect the precise amount and balance of nutrients needed by the broiler, including genetics, age, sex, and environment. Furthermore, broilers in intensive rearing environments will almost always be subjected to some degree of enteric stress that can alter nutrient needs. Exposure to enteric pathogens such as Eimeria spp., the intestinal parasites that cause avian coccidiosis, induces physical damage to the intestinal epithelium and activates immune responses, ultimately resulting in the repartitioning of amino acids (AA) in response to these prioritized demands. Even without any pathogenic challenge, the intestine has an already high demand for many AA, with 30 to 100% of dietary AA extracted during first pass intestinal metabolism. In many cases, increasing dietary protein from intact proteins has been shown to be a viable option to ameliorate impaired AA digestion and absorption and heightened need for certain AA of birds under an enteric stress. However, increasing dietary protein often results in concomitant increases in indigestible protein and carbohydrates that can stimulate the overgrowth of pathogenic bacteria (i.e., Clostridium perfringens). Alternative options to increase dietary AA levels are to increase all feed-grade, free AA (e.g., Met, Lys, Thr, Val), or specific individual feed-grade AA. Therefore, the objectives of this paper are to discuss precision nutrition, the dietary AA demands of the intestine, consequences of coccidiosis on AA needs of the intestine, and formulation approaches to meet these altered needs. In summary, increased dietary protein met by intact proteins has consistently demonstrated its benefits during an Eimeria spp. infection; however, to further the goal of precision nutritional programs, feeding higher levels of a specific AA to support desired functions such as intestinal recovery or immune function for birds experiencing an enteric stress still require further evaluation.

Necrotic enteritis in chickens: a review of pathogenesis, immune responses and prevention, focusing on probiotics and vaccination

Necrotic enteritis (NE), caused by Clostridium perfringens (CP), is one of the most common of poultry diseases, causing huge economic losses to the poultry industry. This review provides an overview of the pathogenesis of NE in chickens and of the interaction of CP with the host immune system. The roles of management, nutrition, probiotics, and vaccination in reducing the incidence and severity of NE in poultry flocks are also discussed.

Starving for nutrients: anorexia during infection with parasites in broilers is affected by diet composition

In 2 experiments, we investigated whether diet composition plays a role in pathogen-induced anorexia, the voluntary reduction in ADFI during infection in broilers. We hypothesized that either energy or CP dietary content could influence the extent of anorexia in Ross 308 broilers and infection outcomes with Eimeria maxima. From d 13 of age, half of the birds were infected, and half were uninfected. ADFI was measured daily, and BW every 3 d until d 29. Oocyst excretion was measured daily from d 17 to 23. The impact of parasitism on the small intestine was assessed on d 19 and 25. In Experiment 1, 336 birds were offered diets progressively diluted with lignocellulose, starting from a diet with 3,105 (kcal ME/kg) and 20% CP. There was a significant interaction between infection and diet on ADFI during the acute stage of infection (d 17 to 21): for control birds diet dilution decreased ADFI and consequently reduced energy and CP intake. For infected birds, diet dilution increased ADFI, leading to the same energy and CP intake across diets. Oocyst excretion and villi length to crypt depth ratio (VCR) were constant across infected treatments. In Experiment 2, 432 birds were offered diets with constant ME (3,105 kcal/kg), but different CP contents (24, 20, 26, and 12%). Infection significantly reduced ADFI. Although there was no interaction between infection and diet on ADFI, there was an interaction on CP intake during the acute stage of infection. Infected birds on the 20% CP diet achieved the same CP intake as uninfected birds. There were no differences in the VCR and ADG of the infected birds on 24, 20 and 16% CP treatments, but birds on 12% had the lowest ADG and excreted more oocysts. We suggest that during infection, birds target a nutrient resource intake, which appears to be beneficial for infection outcomes, while at the same time they avoid excess protein intake. We conclude that different mechanisms regulate ADFI in infected and uninfected birds.

Clostridium perfringens-Induced Host-Pathogen Transcriptional Changes in the Small Intestine of Broiler Chickens

Clostridium perfringens is an important opportunistic pathogen that may result in toxin-mediated diseases involving food poisoning/tissue gangrene in humans and various enterotoxaemia in animal species. It is a main etiological agent for necrotic enteritis (NE), the most financially devastating bacterial disease in broiler chickens, especially if raised under antibiotic-free conditions. Importantly, NE is responsible for losses of six billion US dollars annually in the global poultry industry. To investigate the molecular mechanisms of C. perfringens-induced pathogenesis in the gut and its microbiome mRNA levels in C. perfringens-infected and non-infected hosts, we used RNA sequencing technology to perform transcriptional analysis of both host intestine and microbiome using our NE model. The growth rate was significantly impaired in chickens infected by C. perfringens. In total, 13,473 annotated chicken genes were differentially expressed between these two groups, with ninety-six genes showing statistical significance (|absolute fold changes| > 2.0, adjusted p value < 0.05). Genes involved in energy production, MHC Class I antigen, translation, ribosomal structures, and amino acid, nucleotide and carbohydrate metabolism from infected gut tissues were significantly down-regulated. The upregulated genes were mainly engaged in innate and adaptive immunity, cellular processes, genetic information processing, and organismal systems. Additionally, the transcriptional levels of four crucial foodborne pathogens were significantly elevated in a synergic relationship with pathogenic C. perfringens infection. This study presents the profiling data that would likely be a relevant reference for NE pathogenesis and may provide new insights into the mechanism of host-pathogen interaction in C. perfringens-induced NE infection in broiler chickens.

Effects of low-crude protein diets supplemented with arginine, glutamine, threonine, and methionine on regulating nutrient absorption, intestinal health, and growth performance of Eimeria-infected chickens

The study was conducted to evaluate the effects of low crude protein diets supplemented with arginine, glutamine, methionine, and/or threonine on apparent ileal digestibility of amino acids, intestinal morphology, intestinal permeability, gene expression of nutrient transporters, and tight junction proteins of broiler chickens challenged with mixed Eimeria spp. A total of five hundred seventy-six, 12-day-old male broiler chickens were allocated into 8 treatments, and 6 replicate cages of 12 chickens per cage. This experiment included a nonchallenged control (NC) fed regular corn-soybean meal-based diet (Regular diet, 19% crude protein), an Eimeria-challenged control (CC) fed Regular diet, an Eimeria challenge group fed low-crude protein diet (LCP, 16% crude protein), 4 Eimeria challenge groups fed low-crude protein diet supplemented with 0.75% arginine, glutamine, methionine, and threonine, respectively (ARG, GLN, MET, and THR), and an Eimeria challenge group fed low-crude protein diet with 0.75% supplemented arginine, glutamine, methionine, and threonine collectively as a combination group (COMB). On d 14, birds in the challenge groups were gavaged with a mixed Eimeria spp. solution containing 12,500 oocysts of E. maxima, 12,500 oocysts of E. tenella, and 62,500 oocysts of E. acervulina. The results showed that the Eimeria challenge reduced overall growth performance, but the LCP had no adverse impacts on intestinal health and growth of Eimeria-infected birds compared to the CC. Additionally, supplementation of crystalline arginine, glutamine, methionine, and threonine improved the apparent ileal digestibility of these specific amino acids on 6 dpi. Moreover, the THR treatment increased villus height in the duodenum. The ARG treatment decreased intestinal permeability and gene expression of amino acid transporters, whereas the GLN and THR treatments both reversed adverse effects of coccidiosis on gene expression of tight junction protein (claudin 1). However, the MET and COMB treatments exacerbated infection severity of coccidiosis. In summary, adding 0.75% of arginine, glutamine, or threonine in a low crude protein diet can improve the intestinal health of birds challenged with a mild coccidia infection.

The Influence of a Diet Supplemented with 20% Rye and Xylanase in Different Housing Systems on the Occurrence of Pathogenic Bacteria in Broiler Chickens

Sanitary conditions and diet are important elements determining the occurrence of pathogens in animals. The aim of the research was to assess the effect of an experimental diet with rye and xylanase for broiler chickens in cages and in a free-range system on the intestinal microbiome. The study was carried out in two experimental stages, the first on 224 1-d-old male Ross 308 chickens with an initial weight of 41 g, and the second on 2000 1-d-old male chickens with an initial weight of 42 g. All birds were reared to 42 d of age and fed crumbled starter (1 to 21 d) and pelleted grower–finisher (22 to 42 d) isonitrogenous and isoenergetic diets, supplemented with 20% rye and/or 200 mg/kg xylanase. Directly after slaughter, bacteria were isolated from the cloaca of birds and identified using classical microbiological methods and MALDI-TOF mass spectrometry. The antibiotic susceptibility of the bacteria was assessed by the disc diffusion method. The study showed the presence of abundant bacteria in the gut microbiome of chickens kept in both housing systems. The most frequently isolated bacteria were Escherichia coli, Enterococcus spp., Proteus spp., Campylobacter spp., and Staphylococcus spp. Antibiotic resistance was significantly higher in E. coli, Proteus spp., and Campylobacter spp. obtained from chickens from the free-range farm, but in the case of Enterococcus and Staphylococcus, resistance was higher in bacteria from caged birds. The high antibiotic resistance among pathogens of the gastrointestinal tract necessitates the search for means to control the microbiome in favour of beneficial bacteria. The significant influence of rye and xylanase on the bacterial content may be the basis for the introduction of this method to support the control of pathogens.

Assessment of Immune Response and Efficacy of Essential Oils Application on Controlling Necrotic Enteritis Induced by Clostridium perfringens in Broiler Chickens

Necrotic enteritis (NE) caused by Clostridium perfringens is one of the most important enteric diseases in poultry. The antibacterial activity of two different essential oil (EO) blends against C. perfringens was investigated both in vitro and in vivo. Additionally, the immunological response to EO treatment was assessed. In the in vitro study, the antibacterial activity of EO formulas and commonly used antibiotics was evaluated against C. perfringens using disk diffusion assay, minimum inhibitory concentration (MIC) assay, and minimum bactericidal concentration (MBC) assay. In the in vivo study, NE experimental infection was performed on 440 Ross broiler chicks at 19 days of age for 4 continuous days. The chicks were treated with either EOs or amoxicillin at 22 days of age for 5 continuous days. One day after the end of treatment, the birds’ performance was evaluated by calculating the feed conversion ratio. Serum samples from 120 birds were collected to measure the levels of IL-1β, IFN-γ, IL-8, IL-10, and IL-17. After that, all birds were slaughtered, and their small intestines were subjected to gross and histopathological evaluation. In addition, bacterial counts in the small intestines were evaluated. In the in vitro study, EOs showed higher antimicrobial activities in comparison with antibiotics against C. perfringens. In the in vivo study, birds treated with EOs showed a significant decrease in bacterial counts, a significant decrease in intestinal lesions, and a significant improvement in performance compared with untreated birds (p < 0.05). Moreover, treating birds with EOs directed the immune system toward an anti-inflammatory pathway. None of the treated birds died due to NE compared with the 10% mortality rate in untreated birds. In conclusion, EOs might be an effective and safe alternative to antibiotics in the treatment of chicken NE.

The potential mechanistic insights and future implications for the effect of prebiotics on poultry performance, gut microbiome, and intestinal morphology

Prebiotics may modify the biological processes in the chickens' gastrointestinal tract to improve poultry performance and health. Prebiotics are natural feed additives that offer many economic advantages by decreasing mortality rates, increasing growth rates, and improving birds' feed efficiency. Prebiotic action potentially affects the degradation of indigestible dietary compounds, the synthesis of nitrogen components and vitamins, and simplifies the removal of undesirable elements in the diet. Prebiotics could also induce desirable gut microbiome modifications and affect host metabolism and immune health. It is worth mentioning that gut bacteria metabolize the prebiotic compounds into organic compounds that the host can subsequently use. It is important to limit the concept of prebiotics to compounds that influence the metabolism of resident microorganisms. Any medicinal component or feed ingredient beneficial to the intestinal microecosystem can be considered a prebiotic. In this review, the impacts of prebiotics on the gut microbiome and physiological structure are discussed, emphasizing the poultry's growth performance. The current review will highlight the knowledge gaps in this area and future research directions.

Probiotics and gut health: linking gut homeostasis and poultry productivity

The use of probiotics in poultry production has increased rapidly, and this movement has been promoted by global events, such as the prohibition or decline in the use of antibiotic growth promotants in poultry feeds. There has been a persistent search for alternative feed additives, and probiotics have shown that they can restore the composition of the gut microbiota, and produce health benefits to the host, including improvements in performance. Probiotics have shown potential to increase productivity in poultry, especially in flocks challenged by stressors. However, the outcomes of probiotic use have not always been consistent. There is an increasing demand for well defined products that can be applied strategically, and currently, probiotic research is focusing on delineating their mechanisms of action in the gut that contribute to an improved efficacy. In particular, mechanisms involved in the maintenance and protection of intestinal barrier integrity and the role of the gut microbiota are being extensively investigated. It has been shown that probiotics modulate intestinal immune pathways both directly and through interactions with the gut microbiota. These interactions are key to maintaining gut homeostasis and function, and improving feed efficiency. Research has demonstrated that probiotics execute their effects through multiple mechanisms. The present review describes recent advances in probiotic use in poultry. It focuses on the current understanding of gut homeostasis and gut health in chickens, and how it can be assessed and improved through supplementation of poultry diets with probiotics in poultry diets. In particular, cellular and molecular mechanisms involved in the maintenance and protection of gut barrier structure and function are described. It also highlights important factors that influence probiotic efficacy and bird performance.

Centennial Review: Recent developments in host-pathogen interactions during necrotic enteritis in poultry

Necrotic enteritis (NE) is a significant enteric disease in commercial poultry with considerable economic effect on profitability manifested by an estimated $6 billion in annual losses to the global industry. NE presents a unique challenge, being a complex enteric disease that often leads to either clinical (acute) or subclinical (chronic) form. The latter typically results in poor performance (reduced feed intake, weight gain and eventually higher feed conversion ratio [FCR]) with low mortality rates, and represents the greatest economic impact on poultry production. The use of antibiotic growth promoters (AGPs) has been an effective tool in protecting birds from enteric diseases by maintaining enteric health and modifying gut microbiota, thus improving broilers’ production efficiency and overall health. The removal of AGPs presented the poultry industry with several challenges, including reduced bird health and immunity as well as questioning the safety of poultry products. Consequently, research on antibiotic alternatives that can support gut health was intensified. Probiotics, prebiotics, essential oils, and organic acids were among various additives that have been tested for their efficacy against NE with some being effective but not to the level of AGPs. The focus of this review is on the relationship between NE pathogenesis, microbiome, and host immune responses, along with references to recent reviews addressing production aspects of NE. With a comprehensive understanding of these dynamic changes, new and programmed strategies could be developed to make use of the current products more effectively or build a stepping stone toward the development of a new generation of supplements.

Spirulina platensis Inclusion Reverses Circulating Pro-inflammatory (Chemo)cytokine Profiles in Broilers Fed Low-Protein Diets

Proteins are considered the most expensive nutrients in commercial modern broiler production, and their dietary inclusion at low levels is pivotal to minimize feed costs and reduce nitrogen waste. The quest for an environmentally friendly source of proteins that favor the formulation of low protein diets without compromising broiler health, welfare, and growth performance has become a hotspot in nutrition research. Due to its high protein content, the naturally growing Spirulina microalgae is considered a promising nutrient source. The purpose of the present study was, therefore, to determine the effects of Spirulina supplementation on liver bacterial translocation, hematological profile, and circulating inflammatory and redox markers in broilers fed a low-protein diet. One-day-old Ross 708 male broilers (n = 180) were randomly assigned into one of three experimental treatments: standard diet as a control, low protein diet, and low protein diet supplemented with 100 g/kg of Spirulina. Target molecular markers were measured in the peripheral blood circulation using real-time quantitative PCR. Reducing dietary proteins increased bacterial translocation and systemic inflammation as indicated by proportions of basophils among blood leukocytes. The expression levels of circulating pro-inflammatory cytokines [interleukin (IL)-3, IL-6, IL-4, IL-18, and tumor necrosis factor-α], chemokines (CCL-20), and NOD-like receptor family pyrin domain containing 3 inflammasome were significantly upregulated in birds fed the low protein diet compared with the control. The inclusion of Spirulina reversed these effects, which indicates that Spirulina reduces systemic inflammation- and bacterial translocation-induced by a low protein diet and could be a promising alternative protein source in poultry diets.

Mandated restrictions on the use of medically important antibiotics in broiler chicken production in Canada: implications, emerging challenges, and opportunities for bolstering gastrointestinal function and health– A review

Chicken Farmers of Canada has been progressively phasing out prophylactic use of antibiotics in broiler chicken production. Consequently, hatcheries, veterinarians, and nutritionists have been mandated to contend with less reliance on use of preventive antibiotics. A topical concern is the increased risk of proliferation of enteric pathogens leading to poor performance, increased mortality and compromised welfare. Moreover, the gut harbors several taxa such as Campylobacter and Salmonella capable of causing significant illnesses in humans via contaminated poultry products. This has created opportunity for research and development of dietary strategies designed to modulate gastrointestinal environment for enhanced performance and food safety. Albeit with inconsistent responses, literature data suggests that dietary strategies such as feed enzymes, probiotics/prebiotics and phytogenic feed additives can bolster gut health and function in broiler chickens. However, much of the efficacy data was generated at controlled research settings that vary significantly with the complex commercial broiler production operations due to variation in dietary, health and environmental conditions. This review will summarize implications of mandated restrictions on the preventative use of antibiotics and emerging Canadian broiler production programs to meet processor specifications. Challenges and opportunities for integrating alternative dietary strategies in commercial broiler production settings will be highlighted.

Impact of feeding modified soy protein concentrate in the starter phase on growth performance and gastrointestinal responses in broiler chickens through to day 42 of age

Growth performance and physiological responses of feeding modified soy protein concentrate (MSPC, 72% CP) in the starter phase were investigated. A total of 1,216 d old male Ross x Ross 708 broiler chicks were placed in 32 floor pens based on BW, fed one of 4 (n = 8) corn-soybean meal-based diets formulated with 0, 7.7, 10.0 or 12.5% MSPC for 10 d and transitioned to common diets to d 42. Feed intake, BW, and mortality were measured. Samples of birds were bled on d 10 for plasma uric acid (PUA) and subsequently necropsied for organs weight and samples of pancreatic tissues for enzyme activity, jejunal tissues for enzyme activity and histomorphology and ceca digesta for microbial activity. Litter moisture was determined on d 36 and 42 and sample of birds were necropsied on d 42 for breast yield and ceca digesta sample for microbial activity. Feeding MSPC linearly (P < 0.001) increased starter growth performance. Overall (d 0-42), MSPC linearly (P = 0.05)improved FCR; The FCR was 1.566, 1.535, 1.488 and 1.527 for 0.0, 7.7, 10.0, and 12.5% MSPC, respectively. Feeding MSPC linearly (P ≤ 0.04) increased breast yield and decreased small intestine length, gizzard digesta pH, and PUA. Breast yield was 230, 238, 246, and 252 g/kg BW for 0.0, 7.7, 10.0, and 12.5% MSPC, respectively. Pancreatic and jejunal chymotrypsin and trypsin activities and histomorphology were not (P > 0.10) influenced by the diets. On d 10, MSPC linearly (P < 0.05) reduced ceca digesta abundance of Ruminococcaceae, E. Coli, and Clostridium but increased abundance of Bifidobacterium and the ratio of Lactobacilli and E. Coli. Birds fed MSPC showed linear (P = 0.01) increase in abundance of Bifidobacterium on d 42. Feeding MSPC linearly increased ceca digesta acetic (P = 0.01) and reduced propionic (P = 0.048), and iso butyric (P = 0.003) in 10 d old broiler chicken. In conclusion, up to 12.5% MSPC inclusion in the starter phase increased growth performance through to d 42 linked to enhanced gut health through reduction of enteric pathogens.

Effects of Raw and Fermented Rapeseed Cake on Growth Performance, Methane Production, and Breast Meat Fatty Acid Composition in Broiler Chickens

The study was conducted to evaluate the effects of partial replacement of soybean meal (SBM) by 15% raw or fermented rapeseed cake (RRC or FRC) to broilers' diets on growth performance, nutrient utilization, methane emission, and breast muscle fatty acid (FA) composition. A total of 420 one-day-old female Ros 308 broilers were used in three independent experiments (300 birds in the first experiment and 60 in the second and third experiments). In each trial, three treatments were set up: a control group (without rapeseed), and diets replaced soybean meal with 15% addition of RRC or FRC. Birds fed the FRC diet experienced no effect (p > 0.05) on performance or nutrients utilization. Methane emission and total methanogen population in the ceca was decreased (p < 0.05) with the FRC diet. The concentrations of n-3 and n-6 FAs in the breast tissue of fourteen-day-old birds were not affected (p > 0.05) by FRC. However, the n-6/n-3 ratio in the breast muscle of 28-day-old birds was reduced (p < 0.001). In conclusion, the replacement of SBM by FRC in the broiler diets did not show any unfavorable effects on performance or nutrient utilization. Furthermore, the breast meat FA profile was improved, methanogen counts significantly decreased, and methane emission was limited.

The Effect of Different Species of Eimeria with Clostridium perfringens on Performance Parameters and Induction of Clinical Necrotic Enteritis in Broiler Chickens

Necrotic enteritis (NE) is a common disease that causes great economic loss to the broiler industry due to mortality and reduced performance. Although Clostridium perfringens (CP) is a necessary component of this disease, coccidia species are a well-defined predisposing factor that exacerbates the condition. Different Eimeria species have been reported to influence NE to different degrees. In a pair of experiments, six different Eimeria species were evaluated in the presence and absence of C. perfringens. Male broiler chicks were housed in battery cages for the duration of both experiments. Feed conversion, body weight gain, and NE mortality were reported in both experiments. Experiment 1 challenged birds with E. maxima, E. acervulina, E. tenella, E. necatrix, and E. brunetti at day 13 and subsequently inoculated birds with CP on days 18, 19, and 20. In the second experiment, E. maxima, E. acervulina, E. tenella, and E. praecox were inoculated on day 15 and challenged with CP on days 17, 18, 19, 20, 21, and 22 of the experiment. In the first experiment, E. acervulina, E. brunetti, E. maxima, and E. necatrix with the addition of CP all stimulated necrotic enteritis mortality. In the second experiment, E. praecox had minimal impact on performance during the challenge (14-23 days) while E. maxima + CP decreased body weight gain and increased mortality compared to the CP alone control. Eimeria maxima had the highest mortality (21.9%) in this experiment followed by E. acervulina (6.3%). The remaining Eimeria with added CP in the second experiment did not induce NE mortality. While the challenge with CP alone did not induce mortality, feed conversion was increased compared to the unchallenged control group. When using isolated Eimeria species in these experiments, disturbances created by E. brunetti and E. maxima resulted in the most-severe challenges. These experiments highlight the NE risk of these species of Eimeria and give insight into how other species interact with the host in a controlled CP challenge model.

Physiological Stress Mediated by Corticosterone Administration Alters Intestinal Bacterial Communities and Increases the Relative Abundance of Clostridium perfringens in the Small Intestine of Chickens

A model of physiological stress mediated by the administration of corticosterone (CORT) was used to investigate the impact of stress on the intestinal microbiota of chickens. Birds were administered CORT in their drinking water at 0, 10 (low dose CORT; LDC), and 30 (high dose CORT; HDC) mg/L. Digesta from the small intestine and ceca were examined after 1, 5, and 12 days post-initiation of CORT administration by 16S rRNA gene sequencing. A decrease in phylogenetic diversity and altered composition of bacteria were observed for HDC in the small intestine. Analysis by ANOVA-Like Differential Expression 2 (ALDEx2) showed that densities of Clostridium sensu stricto 1 bacteria were increased in the small intestine for LDC and HDC. Quantitative PCR confirmed that CORT administration increased densities of Clostridium perfringens in the small intestine, but only HDC was associated with increased densities of the bacterium in ceca. Predictive functional analysis by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) showed pathways of carbohydrate metabolism to be enriched with CORT, and amino acid synthesis to be enriched in control birds in the small intestine. In conclusion, physiological stress mediated by CORT modulated bacterial communities in the small intestine and increased densities of C. perfringens. This implicates stress as an important mediator of this important enteric pathogen in poultry.

Clostridium perfringens as Foodborne Pathogen in Broiler Production: Pathophysiology and Potential Strategies for Controlling Necrotic Enteritis

Clostridium perfringens (Cp.) is the cause of human foodborne desease. Meat and poultry products are identified as the main source of infection for humans. Cp. can be found in poultry litter, feces, soil, dust, and healthy birds' intestinal contents. Cp. strains are known to secrete over 20 identified toxins and enzymes that could potentially be the principal virulence factors, capable of degrading mucin, affecting enterocytes, and the small intestine epithelium, involved in necrotic enteritis (NE) pathophysiology, also leading to immunological responses, microbiota modification and anatomical changes. Different environmental and dietary factors can determine the colonization of this microorganism. It has been observed that the incidence of Cp-associated to NE in broilers has increased in countries that have stopped using antibiotic growth promoters. Since the banning of such antibiotic growth promoters, several strategies for Cp. control have been proposed, including dietary modifications, probiotics, prebiotics, synbiotics, phytogenics, organic acids, and vaccines. However, there are aspects of the pathology that still need to be clarified to establish better actions to control and prevention. This paper reviews the current knowledge about Cp. as foodborne pathogen, the pathophysiology of NE, and recent findings on potential strategies for its control.

Facilitating the acceptance of tangibly reduced-crude protein diets for chicken-meat production

Inclusions of non-bound amino acids particularly methionine, lysine and threonine, together with the "ideal protein" concept have allowed nutritionists to formulate broiler diets with reduced crude protein (CP) and increased nutrient density of notionally "essential" amino acids and energy content in recent decades. However, chicken-meat production has been projected to double between now and 2050, providing incentives to reduce dietary soybean meal inclusions further by tangibly reducing dietary CP and utilising a larger array of non-bound amino acids. Whilst relatively conservative decreases in dietary CP, in the order of 20 to 30 g/kg, do not negatively impact broiler performance, further decreases in CP typically compromise broiler performance with associated increases in carcass lipid deposition. Increases in carcass lipid deposition suggest changes occur in dietary energy balance, the mechanisms of which are still not fully understood but discourage the acceptance of diets with reductions in CP. Nevertheless, the groundwork has been laid to investigate both amino acid and non-amino acid limitations and propose facilitative strategies for adoption of tangible dietary CP reductions; consequently, these aspects are considered in detail in this review. Unsurprisingly, investigations into reduced dietary CP are epitomised by variability broiler performance due to the wide range of dietary specifications used and the many variables that should, or could, be considered in formulation of experimental diets. Thus, a holistic approach encompassing many factors influencing limitations to the adoption of tangibly reduced CP diets must be considered if they are to be successful in maintaining broiler performance without increasing carcass lipid deposition.

Combination of Bacillus licheniformis and Salinomycin: Effect on the Growth Performance and GIT Microbial Populations of Broiler Chickens

Simple Summary

The beneficial effects of Bacillus spp. probiotic preparations used for poultry are well-documented and characterized by growth performance improvement and positive modulation of gastrointestinal tract (GIT) microbiota. Moreover, the favorable influence of salinomycin has been frequently studied as an ionophore coccidiostat, as well as an antimicrobial agent. However, limited data are available in terms of the parallel usage of both Bacillus licheniformis DSM 28710 and salinomycin in poultry diets. From a practical point of view, evaluating the potential interactions between this species and agent is crucial to assess their parallel usage, and the current study confirmed the positive effect of their mixture on the modulation of pH value in the crop and ceca, as well as the GIT microbiota, especially in the jejunum and ceca. Additionally, the results obtained in this study show positive effects of B. licheniformis on the growth performance, as well as the influence of both experimental factors used separately in the case of GIT microbiota modulations.

Abstract

The aim of the study was to investigate the effect of Bacillus licheniformis and salinomycin supplementation in broiler diets as individual factors or in combination on the growth performance, GIT morphometry, and microbiota populations. Four hundred one-day-old Ross 308 chicks were randomly distributed to four dietary treatments (10 replicates, 10 birds each). The following treatments were applied: NC—no additives; NC + SAL—salinomycin addition (60 mg/kg diet), NC + PRO—B. licheniformis DSM 28710 preparation (1.6 × 10⁹ CFU/kg; 500 mg/kg diet), and NC + SAL + PRO—combination of salinomycin and B. licheniformis. Probiotic administration resulted in improvement (p < 0.05) of the performance parameters, including body weight gain (1–10 d, and 11–22 d) and feed conversion ratio (11–22 d, 1–36 d). An interaction (p < 0.05) between experimental factors was observed in terms of lower pH values in the crop (tendency, p = 0.053) and ceca. Both factors lowered the alpha diversity and Enterobacteriaceae and promoted Bacillaceae communities in the jejunum (p < 0.05). Interactions were also observed in terms of reducing Clostridiaceae in the ceca. In conclusion, the combined use of B. licheniformis and salinomycin in broilers’ diets had beneficial effects.

Supplementing glycine, serine, and threonine in low protein diets for meat type chickens

Reducing dietary protein has been of interest to the global poultry industry to improve bird health, welfare, and industry sustainability. Low protein (LP) diets are typically glycine (Gly) deficient and produce poor performance. Supplementing the diet with Gly or precursors of Gly can overcome this deficiency. A feeding experiment was conducted with 330 Ross 308 off-sex males across 5 treatments in a randomized design using 11 birds per pen replicated 6 times. Grower and finisher treatments were fed from day 7 to 21 and day 21 to 35, respectively. The objective was to test the efficacy of supplementation with Gly and Gly equivalents (Glyequiv), serine (Ser) and threonine (Thr), in plant-based LP diets on bird performance against a standard protein (SP) diet containing meat and bone meal. Glycine, Ser, or Thr were supplemented on Glyequiv basis to an approximately 3% lower CP diet to achieve the same digestible Gly and Ser level as the SP diet. Nitrogen efficiency, serum uric acid, blood plasma amino acids (AA) and AA digestibility were also investigated to monitor potential metabolic effects. Birds fed the LP diet were only 3.3% lower in final body weight than the SP treatment (2,556 vs. 2,641 g) while the supplementation of Gly or Ser had no effect. Supplementation of Thr reduced final body weight by 9.5% (P < 0.05). Reducing CP increased N efficiency by 9.6% (P < 0.05) and decreased blood serum uric acid by 26.9% (P < 0.001) in the finisher treatments. Glycine and Ser supplementation in LP diets had no effect on these parameters. The LP diet reduced AA digestibility and blood plasma AA while the supplementation with either Gly, Ser, or Thr increased overall AA digestibility (P < 0.05) but had no overall effect on blood plasma AA. Further research is required into Gly metabolism; however, Thr supplementation depressed growth and therefore is not feasible to cover Gly deficiency in LP diets on a Glyequiv basis.

Reducing protein and supplementing crystalline amino acids, to alter dietary amino acid profiles in birds challenged for subclinical necrotic enteritis

Necrotic enteritis (NE) is an infection of the gastrointestinal tract and is estimated to cost the global poultry industry billions of dollars annually. A study was conducted to examine whether reducing the crude protein might offset the severity of NE in broilers experimentally challenged with Eimeria spp. on day 9 and Clostridium perfringens on days 14 and 15. Furthermore, increasing the dietary amino acid (AA) density of the diet was also examined owing to identified benefits of improving performance compromised from low protein (LP) diets or NE. A 2 × 2 × 3 factorial arrangement of treatments at 6 replicates per treatment was used with 972 Ross 308 cockerels fed wheat-sorghum-soy-based diets to 35 D. Factors were NE challenge: no or yes; protein: standard (SP) or LP; and AA density: 100% AA, 115% with only essential AA (115% EAA) increased, and 115% AA with both essential and nonessential AA (115% AA) increased. The performance was measured in grower (days 7–21), finisher (days 21–35), and overall (day 7–35) periods. In addition, on day 16, intestinal lesion score and cecal short-chain fatty acids were measured. Only in nonchallenged birds fed LP diets, 115% AA increased grower feed intake (P < 0.01) and body weight gain (P < 0.05) compared to 115% EAA treatments. Challenge increased jejunal lesions (P < 0.001) with no difference between dietary treatments. Finisher body weight gain was greater in nonchallenged birds fed the 115% AA diets than in challenged birds (P < 0.05). Feeding diets with higher nonessential AA encouraged faster recovery from NE challenge. When fed the SP diets, NE challenge increased cecal butyric acid (P < 0.01) and total short-chain fatty acids (P < 0.05). The nutrient matrix used in LP diets does not favor beneficial butyric acid–producing bacteria. Using LP diets to mitigate NE severity does not offset the predisposing effect of E. spp. when attacking the gastrointestinal tract, and NE recovery is favored when feeding SP diets or additional AA.

Incidence of Bacterial Chondronecrosis with Osteomyelitis (Femoral Head Necrosis) Induced by a Model of Skeletal Stress and its Correlation with Subclinical Necrotic Enteritis

Bacterial chondronecrosis with osteomyelitis (BCO) is a septic necrosis of the skeletal system of unknown origin and an important cause of lameness in broiler chickens. Epithelial inflammation has been proposed as an avenue for bacterial translocation leading to BCO. We evaluated the effect of subclinical necrotic enteritis (SNE), an intestinal inflammatory event, with the development of BCO. In each of two experiments, chickens were divided into three treatments: (1) SNE challenge, including both dietary (wheat- and fish-based diet) and intestinal pathogenic challenges (Eimeria maxima and Clostridium perfringens), (2) dietary challenge only, and (3) control diet (corn-and soy-based diet). Floor ramps were introduced as part of an established method for increasing the frequency of BCO. The efficacy of the SNE challenge was corroborated by necropsy evaluation of a representative sample of the population. At the end of each experiment, all birds were evaluated for BCO. A high incidence of BCO was found, even in birds with no external signs of lameness. However, the incidence of BCO was not correlated with the intestinal challenge. Conclusions: under the conditions used in these studies, a treatment that is associated with severe damage to the intestinal mucosa does not change the incidence of BCO in broiler chickens.

Dietary Factors as Triggers of Low-Grade Chronic Intestinal Inflammation in Poultry

Inflammation is the reaction of the immune system to an injury; it is aimed at the recovery and repair of damaged tissue. The inflammatory response can be beneficial to the animal since it will reestablish tissue homeostasis if well regulated. However, if it is not controlled, inflammation might lead to a chronic response with a subsequent loss of tissue function. The intestine is constantly exposed to a number of environmental triggers that stimulate inflammation and lead to a reduction in performance. The diet and dietary components constitute consistent inflammatory triggers in poultry. Dietary components, such as anti-nutritional compounds, oxidized lipids, mycotoxins, and excess of soluble fiber or protein, are all capable of inducing a low-grade inflammatory response in the intestine of broilers throughout a 5-week grow-out period. We hypothesized that dietary factor-induced chronic intestinal inflammation is a key driver of the lower performance and higher incidence of intestinal problems observed in poultry production. Therefore, this review was aimed at exploring feed-induced chronic inflammation in poultry, the constituents of the diet that might act as inflammatory triggers and the possible effects of chronic intestinal inflammation on the poultry industry.

The netB-positive Clostridium perfringens in the experimental induction of necrotic enteritis with or without predisposing factors

The netB-positive Clostridium perfringens has been considered as the requisite to consistently induce necrotic enteritis (NE). However, use of a netB-positive strain did not guarantee consistent NE reproduction unless high protein diets or Eimeria, conceived as 2 major predisposing factors, was incorporated. To establish a refined model, the roles of dietary fishmeal inclusion, Eimeria inoculation, and netB-positive C. perfringens challenge in NE induction and the confounding effects of Eimeria infection on NE were examined. The results showed that the use of netB-positive C. perfringens without a predisposing factor failed to induce NE. Fishmeal incorporation promoted the occurrence of NE but did not significantly affect the incidence of the disease in conjunction with challenge of netB-positive C. perfringens. However, the additional participation of Eimeria infection in the same induction procedure produced significantly higher numbers of NE cases and promoted more severe lesions in chickens (P < 0.05). Inoculation of Eimeria resulted in a significant higher incidence of NE compared to the non-Eimeria treated group (P < 0.05). The results demonstrated that both netB-positive C. perfringens and predisposing factors were required for the reproduction of disease. Mild-to-moderate coccidial infection (coccidial lesion score ≤ 2) was noted in NE cases in this model but severe coccidial infection did not correlate with the occurrence of NE, indicating mild coccidial infection may be beneficial for the development of NE. If multiple species infection of Eimeria precedes the challenge of C. perfringens, days 19 to 21 (1 to 3 D after the last clostridial challenge) was the time period favorable for observations of NE lesions. The time after this period may be subject to bias of severity, incidence, or mortality of NE owing to the profound coccidial lesions in the intestinal region. This study demonstrated that the co-infection with netB-positive C. perfringens and Eimeria species under fishmeal incorporation produced a desirable NE model, being of value in studying the effectiveness of novel feed additives and alternative mitigation strategies to prevent NE.

Nisin as a Novel Feed Additive: The Effects on Gut Microbial Modulation and Activity, Histological Parameters, and Growth Performance of Broiler Chickens

Two independent experiments were performed to evaluate the effect of nisin alone or with monensin on gut microbiota, gut microbial activities, and histomorphology (exp 1) and the effect of nisin application in a dose‒response manner on the growth performance of broiler chickens (exp 2). A total of 900 one-day-old female Ross 308 chicks (400, exp 1; 500, exp 2) were randomly distributed to four groups (exp 1; 10 replicate pens per treatment with 10 birds each), i.e., NA, no additives; MON, monensin (100 ppm); NIS, nisin (2700 IU/kg diet); and MON + NIS, a mixture of monensin (100 ppm) and nisin (2700 IU/kg diet); or 5 treatments (exp 2), NA, no additives; NIS100, nisin (100 IU/kg diet); NIS200, nisin (200 IU/kg diet); NIS400, nisin (400 IU/kg diet); and NIS800, nisin (800 IU/kg diet). Nisin supplementation positively affected the microbiota of the gut by reducing potentially pathogenic bacterial populations in the jejunum and ceca. The bacterial fermentation in the jejunum was significantly lowered by nisin addition. The addition of nisin from 100 IU to 800 IU decreased the FCR value over the entire experimental period. According to the results, nisin can be considered a natural dietary supplement for broiler chickens.

The influence of indigestible protein on the performance and meat quality of broilers vaccinated for coccidiosis

High dietary protein and the use of poorly digested protein sources have been suggested to negatively impact broiler health, possibly because of protein fermentation in the distal intestinal tract. The effect of dietary protein levels with low or high indigestible protein fractions (LIP or HIP) on male and female broiler performance were evaluated. The trial was completely randomized with a 2 × 3 × 2 factorial arrangement, where gender, dietary protein levels (24, 26, and 28%), and dietary protein digestible fractions were the main factors. Ross 308 male (1944) and female (2232) were allocated to 72 pens with 54 males or 62 females per pen. Six grower diets 24-LIP, 24-HIP, 26-LIP, 26-HIP, 28-LIP, and 28-HIP were fed from 0 to 32 D of age. Birds were vaccinated with Coccivac-B52 on day 5, and feed intake and BW were recorded on 0, 12, 22, and 32 D. On day 32, 24 birds per treatment were processed for meat yield. Males were heavier than females at all post-hatch ages and the LIP birds were heavier than their HIP counterparts on 32 D. On day 22, birds fed 24 and 26% CP were heavier than those fed 28% CP. Birds fed the 28-LIP diet consumed less total feed than their 24 and 26-LIP equivalents. Birds fed 24% CP had the highest total feed to gain ratio, whereas LIP fed birds had a lower total feed to gain than those fed HIP diets. LIP diets resulted in higher total mortality than the HIP diets. Carcass yield was higher for females than males, increased with CP level, and was lower in HIP than LIP birds. An interaction between CP level and protein digestibility resulted in the 26 and 28-LIP having higher breast yield than all other diets. In conclusion, broiler growth performance and meat yield were affected by dietary indigestible protein alone or in combination with gender and dietary CP level.

Bacillus amyloliquefaciens CECT 5940 alone or in combination with antibiotic growth promoters improves performance in broilers under enteric pathogen challenge

A study was conducted to investigate the effects of Bacillus amyloliquefaciens CECT 5940 as a direct-fed microbial (DFM) alone or in association with bacitracin methylene disalicylate (BMD) in broilers under enteric pathogen challenge. A total of 1,530-day-old male Cobb500 chicks were randomly assigned to 5 treatments, with 9 replicate pens with 34 birds each. Treatments included positive control (PC, basal diet without additives or challenge); negative control (NC, basal diet without additive and challenged birds); NC + 0.05 g/kg BMD; NC + 1 g/kg DFM (10⁶ CFU B. amyloliquefaciens CECT 5940/g of feed); and NC + 0.05 g/kg BMD + 1 g/kg DFM. The challenge consisted of oral gavage with Eimeria maxima and Clostridium perfringens inoculum. Body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR) were evaluated on days 21, 35, and 42. Ileal and cecal content were collected on days 21 and 28 for C. perfringens enumeration by real-time PCR assay and the intestinal health was evaluated by scores. Uniformity (UN), carcass (CY), and breast meat yields (BMY) were evaluated on day 42. After 14 and 21 d post-inoculation, birds in the challenged groups had significant lower FI and BWG compared to the PC group (P < 0.05). However, the groups receiving DFM, BMD, or its combination presented better FCR, CY, BMY, UN, and lower incidence of footpad lesion and litter quality visual scores, compared to the NC group without feed additives (P < 0.05). Mortality was not affected by treatments (P > 0.05). Broilers fed DFM, BMD, or its combination presented lower C. perfringens in ileal content at 21 and 28 d compared to NC group without additives (P < 0.05) and also maintained gut health by keeping the frequency of ballooning, abnormal content, and swollen mucosa comparable to the PC group (P > 0.05). The study indicates that Bacillus amyloliquefaciens CECT 5940 is effective as BMD to provide similar performance and gut health in challenged broilers.

Broilers fed a low protein diet supplemented with synthetic amino acids maintained growth performance and retained intestinal integrity while reducing nitrogen excretion when raised under poor sanitary conditions

The present study investigated the effects of supplementing a low protein (LP) diet supplemented with key essential amino acids (AA) to broilers on growth performance, intestinal tract function, blood metabolites, and nitrogen excretion when the animals were maintained under various sanitary conditions for 35 D after hatching. Three hundred eighty-four one-day-old male broilers (Ross 308) were randomly allotted to groups that received one of 6 dietary treatments in a 2 × 3 factorial arrangement (i.e., 2 environmental conditions and 3 dietary treatments) to give 8 replicates per treatment. Broilers were challenged with 2 environmental conditions (sanitary vs. poor sanitary). The dietary treatments were (1) high protein (HP) diet, (2) LP diet, and (3) LP diet with synthetic key essential AA (LPA): the LP diet was supplemented with synthetic AA up to the required levels for broilers. On day 14, birds consumed the LP diet impaired growth performance compared with those fed the HP diet, while the average daily weight gain-to-feed conversion ratio of birds fed the LPA diet improved to the level of birds fed the HP diet under poor sanitary conditions (P < 0.05). Broilers raised under poor sanitary conditions and fed the LP diet displayed higher (P < 0.05) zonula occludens (ZO-1) expression on day 14 than broilers fed either the HP or LPA diet. Under sanitary conditions, birds fed HP and LPA diets showed higher villus height and crypt depth compared with those of broilers fed the LP diet on day 35. Moreover, broilers raised in the poor sanitary environment had higher (P < 0.05) serum endotoxins than those raised in the sanitary environment. Broilers fed the LPA diet showed reduced (P < 0.05) nitrogen excretion on days 14 and 35 compared with those fed the LP and HP diets independent of the environment. In conclusion, the LPA diet did not impair growth performance under poor sanitary conditions for 14 D after hatch while resulting in lower nitrogen excretion in any environment conditions throughout the experiment.

Genomic analysis on broiler-associated Clostridium perfringens strains and exploratory caecal microbiome investigation reveals key factors linked to poultry necrotic enteritis

Background

Clostridium perfringens is a key pathogen in poultry-associated necrotic enteritis (NE). To date there are limited Whole Genome Sequencing based studies describing broiler-associated C. perfringens in healthy and diseased birds. Moreover, changes in the caecal microbiome during NE is currently not well characterised. Thus, the aim of this present study was to investigate C. perfringens virulence factors linked to health and diseased chickens, including identifying putative caecal microbiota signatures associated with NE.

Results

We analysed 88 broiler chicken C. perfringens genomes (representing 66 publicly available genomes and 22 newly sequenced genomes) using different phylogenomics approaches and identified a potential hypervirulent and globally-distributed clone spanning 20-year time-frame (1993-2013). These isolates harbored a greater number of virulence genes (including toxin and collagen adhesin genes) when compared to other isolates. Further genomic analysis indicated exclusive and overabundant presence of important NE-linked toxin genes including netB and tpeL in NE-associated broiler isolates. Secondary virulence genes including pfoA, cpb2, and collagen adhesin genes cna, cnaA and cnaD were also enriched in the NE-linked C. perfringens genomes. Moreover, an environmental isolate obtained from farm animal feeds was found to encode netB, suggesting potential reservoirs of NetB-positive C. perfringens strains (toxinotype G). We also analysed caecal samples from a small sub-set of 11 diseased and healthy broilers for exploratory microbiome investigation using 16S rRNA amplicon sequencing, which indicated a significant and positive correlation in genus Clostridium within the wider microbiota of those broilers diagnosed with NE, alongside reductions in beneficial microbiota members.

Conclusions

These data indicate a positive association of virulence genes including netB, pfoA, cpb2, tpeL and cna variants linked to NE-linked isolates. Potential global dissemination of specific hypervirulent lineage, coupled with distinctive microbiome profiles, highlights the need for further investigations, which will require a large worldwide sample collection from healthy and NE-associated birds.

The Effect of Clostridium butyricum on Gut Microbiota, Immune Response and Intestinal Barrier Function During the Development of Necrotic Enteritis in Chickens

Necrotic enteritis (NE) causes huge economic losses to the poultry industry. Probiotics are used as potential alternatives to antibiotics to prevent NE. It is known that Clostridium butyricum can act as a probiotic that can prevent infection. However, whether or not it exerts a beneficial effect on NE in chickens remains elusive. Therefore, we investigated the impact of C. butyricum on immune response and intestinal microbiota during the development of NE in chickens, including experimental stages with basal diets, high-fishmeal-supplementation diets, and Clostridium perfringens challenge. Chickens were divided into two groups from day 1 to day 20: one group had its diet supplemented with C. butyricum supplementation and one did not. At day 20, the chickens were divided into four groups: C. perfringens challenged and unchallenged chickens with and without C. butyricum supplementation. All groups were fed a basal diet for 13 days and thereafter a basal diet with 50% fishmeal from day 14 to 24. Chickens were infected with C. perfringens from day 21 to 23. At days 13, 20 and 24, samples were collected for analysis of the relative expression of immune response and intestinal mucosa barrier-related genes and intestinal microbes. The results show that C. butyricum can inhibit the increase in IL-17A gene expression and the reduction in Claudin-1 gene induced-expression caused by C. perfringens challenge. Moreover, C. butyricum was found to increase the expression of anti-inflammatory IL-10 in infected chickens. Although C. butyricum was found to have a significant beneficial effect on the structure of intestinal bacteria in the basal diet groups and decrease the abundance of C. perfringens in the gut, it did not significantly affect the occurrence of intestinal lesions and did not significantly correct the shift in gut bacterial composition post C. perfringens infection. In conclusion, although C. butyricum promotes the expression of anti-inflammatory and tight junction protein genes and inhibits pro-inflammatory genes in C. perfringens-challenged chickens, it is not adequate to improve the structure of intestinal microbiota in NE chickens. Therefore, more effective schemes of C. butyricum supplementation to prevent and treat NE in chickens need to be identified.