Temporary feed restriction partially protects broilers from necrotic enteritis

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.

Transmission of antimicrobial resistance (AMR) during animal transport

The transmission of antimicrobial resistance (AMR) between food-producing animals (poultry, cattle and pigs) during short journeys (< 8 h) and long journeys (> 8 h) directed to other farms or to the slaughterhouse lairage (directly or with intermediate stops at assembly centres or control posts, mainly transported by road) was assessed. Among the identified risk factors contributing to the probability of transmission of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs), the ones considered more important are the resistance status (presence of ARB/ARGs) of the animals pre-transport, increased faecal shedding, hygiene of the areas and vehicles, exposure to other animals carrying and/or shedding ARB/ARGs (especially between animals of different AMR loads and/or ARB/ARG types), exposure to contaminated lairage areas and duration of transport. There are nevertheless no data whereby differences between journeys shorter or longer than 8 h can be assessed. Strategies that would reduce the probability of AMR transmission, for all animal categories include minimising the duration of transport, proper cleaning and disinfection, appropriate transport planning, organising the transport in relation to AMR criteria (transport logistics), improving animal health and welfare and/or biosecurity immediately prior to and during transport, ensuring the thermal comfort of the animals and animal segregation. Most of the aforementioned measures have similar validity if applied at lairage, assembly centres and control posts. Data gaps relating to the risk factors and the effectiveness of mitigation measures have been identified, with consequent research needs in both the short and longer term listed. Quantification of the impact of animal transportation compared to the contribution of other stages of the food-production chain, and the interplay of duration with all risk factors on the transmission of ARB/ARGs during transport and journey breaks, were identified as urgent research needs.

Necrotic enteritis in broiler chickens: disease characteristics and prevention using organic antibiotic alternatives – a comprehensive review

In line with the substantial increase in the broiler industry worldwide, Clostridium perfringens-induced necrotic enteritis (NE) became a continuous challenge leading to high economic losses, especially after banning antimicrobial growth promoters in feeds by many countries. The disease is distributed worldwide in either clinical or subclinical form, causing a reduction in body weight or body weight gain and the feed conversion ratio, impairing the European Broiler Index or European Production Efficiency Factor. There are several predisposing factors in the development of NE. Clinical signs varied from inapparent signs in case of subclinical infection (clostridiosis) to obvious enteric signs (morbidity), followed by an increase in mortality level (clostridiosis or clinical infection). Clinical and laboratory diagnoses are based on case history, clinical signs, gross and histopathological lesions, pathogenic agent identification, serological testing, and molecular identification. Drinking water treatment is the most common route for the administration of several antibiotics, such as penicillin, bacitracin, and lincomycin. Strict hygienic management practices in the farm, careful selection of feed ingredients for ration formulation, and use of alternative antibiotic feed additives are all important in maintaining broiler efficiency and help increase the profitability of broiler production. The current review highlights NE caused by C. perfringens and explains the advances in the understanding of C. perfringens virulence factors involved in the pathogenesis of NE with special emphasis on the use of available antibiotic alternatives such as herbal extracts and essential oils as well as vaccines for the control and prevention of NE in broiler chickens.

Environmental Stress in Chickens and the Potential Effectiveness of Dietary Vitamin Supplementation

Environmental stressors can promote the vulnerability of animals to infections; it is therefore, essential to understand how stressors affect the immune system, the adaptive capacity of animals to respond, and effective techniques in managing stress. This review highlights scientific evidence regarding environmental stress challenge models and the potential effectiveness of vitamin supplementation. The major environmental stressors discussed are heat and cold stress, feed restriction, stocking density, and pollutants. Much work has been done to identify the effects of environmental stress in broilers and layers, while few involved other types of poultry. Studies indicated that chickens' performance, health, and welfare are compromised when challenged with environmental stress. These stressors result in physiological alterations, behavioral changes, decreased egg and meat quality, tissue and intestinal damage, and high mortalities. The application of vitamins with other nutritional approaches can help in combating these environmental stressors in chickens. Poultry birds do not synthesize sufficient vitamins during stressful periods. It is therefore suggested that chicken diets are supplemented with vitamins when subjected to environmental stress. Combination of vitamins are considered more efficient than the use of individual vitamins in alleviating environmental stress in chickens.

Effects of Replacing In-feed Antibiotics with Synergistic Organic Acids on Growth Performance, Health, Carcass, and Immune and Oxidative Statuses of Broiler Chickens Under Clostridium perfringens Type A Challenge

This study was conducted to investigate the effects of replacing in-feed antibiotics with synergistic organic acids on growth performance, health, carcass, and immune and oxidative statuses of broiler chickens under Clostridium perfringens (CP) type A challenge. Two organic acid products were tested: organic acid 1 (OA1), consisting of butyrate, medium-chain fatty acids, organic acids, and phenolics; and organic acid 2 (OA2), consisting of buffered short-chain fatty acids. Six hundred 1-day-old male Arbor Acres broiler chicks were randomly assigned to one of five treatments: Control 1, basal diet, nonchallenged birds; Control 2, basal diet, with CP challenge; antimicrobial growth promoters (AGP), basal diet supplemented with Aureomycin (chlortetracycline), with CP challenge; OA1, basal diet supplemented with OA1, with CP challenge; and OA1OA2, basal diet supplemented with OA1 and OA2, with CP challenge. Each treatment had eight replicate pens of 15 birds. The experiments lasted for 29 days. The disease challenge was performed on days 15-17, with an oral gavage of 0.5 mL of CP culture (2.0 × 108 colony-forming units [CFU]/mL) for each bird. Body weights (BWs), intestinal lesion scores, immune organ indices, and serum malondialdehyde (MDA) concentrations were measured on days 19, 22, and 29, respectively, in three birds per pen. Carcass characteristics were determined on day 29. No treatment-related differences in mortality were noted before (P = 0.28) or after (P = 0.64) challenge or over the whole study period (days 0-28; P = 0.66). On day 19, the BW of Control 2 was lower than other treatments (P < 0.0001). On day 22, AGP, OA1, and OA1OA2 had higher BW than Control 2 (P = 0.001). The breast muscle yield of OA1 and OA1OA2 was higher than AGP (P < 0.05). The abdominal fat yield of OA1OA2 was lower than AGP and Control 2 (P < 0.05). On day 22, the birds fed OA1OA2 showed lower intestinal lesion scores than OA1 (P < 0.05). No treatment-related differences in immune organ (spleen, thymus, and bursa) indices were noted (P > 0.05). On day 29, the MDA concentration of OA1 and OA1OA2 was lower than those of Control 1 and AGP (P < 0.05). In conclusion, the addition of organic acids may protect broiler chickens from severe intestinal lesions and oxidative stress and may help reduce abdominal fat mass deposition. There is potential for organic acid-based products as alternatives for AGP in preventing necrotic enteritis in broilers.

Habitat selection and populations of Corynosoma (Acanthocephala) in the intestines of sea otters (Enhydra lutris) and seals

Acanthocephalans are common intestinal parasites of marine mammals, the most widespread of which is the genus Corynosoma. In this study, parasite infrapopulations of two closely related species of Corynosoma were examined: Corynosoma enhydri from sea otters (Enhydra lutris) in Alaska (n = 12) and California (n = 19), and Corynosoma strumosum from seals in Germany (n = 22). Prevalence of C. enhydri was 100% in Californian otters, with a mean abundance of 30, and 83% in Alaskan otters, with a mean abundance of 232. In seals, C. strumosum had a prevalence of 65%, with a mean abundance of 33. Female C. enhydri dominated both Californian (82%) and Alaskan (79%) infections, while, in seals, female C. strumosum made up 68% of the parasite population. Reproduction rates for C. enhydri, with 16% (California) and 18% (Alaska) of females mated, were low compared to C. strumosum in seals, of which 40% of females were mated. Habitat selection also differed significantly between the two species. Corynosoma enhydri was found most frequently in the second and third fifths of the small intestine, while C. strumosum was found most frequently in the fourth. The differences in habitat selection and prevalence analysed in this study may be related to a trade-off between growth and reproduction between the two species.

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.

The Effect of Whey on Performance, Gut Health and Bone Morphology Parameters in Broiler Chicks

Whey is a highly nutritious byproduct of the cheese industry that can be used effectively in the animal feed industry. However, the use of whey in poultry diets is limited by its high lactose and mineral contents. The objective of the present study was to evaluate the effect of different concentrations of whey in poultry diets on the performance, intestinal microbiota and physico-chemical parameters of the intestinal ecosystem, as well as on the bone morphology and its strength in broiler chicks. One hundred and twenty-eight, day-old, male broiler chicks were randomly allocated into four treatment groups of 32 chicks each. The treatment groups were: group A, which served as negative control and groups B, C and D, supplemented with 1, 2 and 5% of dietary whey, respectively. Performance of the groups was evaluated throughout the experiment. Following necropsies, the gastrointestinal tract from each bird was removed, divided into its anatomical parts and intestinal samples were taken for microbiological analysis and for pH and viscosity measurement as well. Tibiotarsus was also collected for morphometric analysis and strength evaluation. The statistical analysis of the experimental data revealed that the dietary supplementation of 1 and 2% of whey improved significantly (p ≤ 0.05) the body weight, while the addition of 5% of whey reduced significantly (p ≤ 0.05) the body weight. Furthermore, the addition of 1, 2 and 5% of dietary whey increased significantly (p ≤ 0.05) the pH of jejunum digesta and reduced significantly (p ≤ 0.05) the pH of caecum digesta compared to the control group. The addition of 1 and 2% of whey reduced significantly (p ≤ 0.05) the viscosity in the jejunum and ileum digesta, compared to the addition of 5% of whey which reduced significantly (p ≤ 0.05) the viscosity in jejunum digesta but increased significantly (p ≤ 0.05) the viscosity in ileum digesta. Moreover, the addition of 1, 2 and 5% of dietary whey increased significantly (p ≤ 0.05) the caecal counts of Lactobacillus spp. and Lactococcus lactis, while the addition of 5% of whey reduced significantly (p ≤ 0.05) the tibiotarsus length. It can be concluded that the addition of low quantities of whey up to 2% promoted the performance and gut health of birds, while the addition of higher quantities of whey at the level of 5% had a detrimental effect on the performance and tibiotarsus length.

Rapid growth predisposes broilers to necrotic enteritis

Over the past 50 years, intentional genetic selection within the broiler industry has led to major improvements in both body weight gain (BWG) and feed conversion efficiency. Next to its economic advantages, enhancing BWG can increase the risk of metabolic and skeletal disorders. The aim of this study was to examine whether higher BWG is a predisposing factor for broiler necrotic enteritis. In this study, 300 broilers were challenged with Clostridium perfringens using a well-established, previously described challenge model. It was found that birds with higher body weight (BW) and BWG before challenge were predisposed to develop more severe necrotic enteritis lesions. After challenge, the average BWG of the birds developing mild to severe lesions dropped significantly, negatively affecting bird welfare and performance. These results show a significant interplay between BWG and the development of necrotic enteritis lesions. This raises the question whether there is a limit to broiler performance with respect to maintaining intestinal health, and whether decreasing BWG (at certain stages of the growth cycle) can be part of a plan to prevent intestinal pathology. RESEARCH HIGHLIGHTS Higher body weight is a predisposing factor to necrotic enteritis in broilers.

Intestinal microbiota of broilers submitted to feeding restriction and its relationship to hepatic metabolism and fat mass: Fast-growing strain

The present study was conducted to verify how feed restriction affects gut microbiota and gene hepatic expression in broiler chickens and how these variables are related to body weight gain. For the experiment, 21-d-old Cobb500^TM birds were distributed in a completely randomized experimental design with three treatments: T1. Control (ad libitum-3.176 Mcal/kg ME-metabolizable energy-and 19% CP-crude protein); T2. Energetic restriction (2.224 Mcal/kg ME and 19% CP) from 22 to 42 days with consumption equivalent to control; T3. Quantitative restriction (70% restriction, i.e., restricted broilers ingested only 30% of the quantity consumed by the control group-3.176 Mcal/kg ME and 19% CP) for 7 days, followed by refeeding ad libitum from 28 to 42 days. Ileum and caecum microbiota collections were made at 21, 28 and 42 days of age. Hepatic tissue was collected at 28 and 42 days old for relative gene expression analyses. At 43-d-old, body composition was quantified by DXA (Dual-energy X-ray Absorptiometry). Both feed restriction programmes decreased Lactobacillus and increased Enterococcus and Enterobacteriaceae counts. No differences were found in the refeeding period. Energetic restriction induced the expression of CPT1-A (Carnitine palmitoyltransferase 1A) gene, and decreased body fat mass. Quantitative feed restriction increased lipogenic and decreased lipolytic gene expression. In the refeeding period, CPT1-A gene expression was induced, without changing the broilers body composition. Positive associations were found between BWG (Body Weight Gain) and Lactobacillus and Clostridium cluster IV groups, and negatively associations with Enterobacteriaceae and Enterococcus bacterial groups. In conclusion, differences found in microbiota were similar between the two feed restriction programmes, however, hepatic gene expression differences were only found in quantitative restriction. Higher counts of Lactobacillus and Clostridium cluster IV groups in ileum are likely to be related to better broiler performance and low expression of lipogenic genes.

Effect of early dietary energy restriction and phosphorus level on subsequent growth performance, intestinal phosphate transport, and AMPK activity in young broilers

We aimed to determine the effect of low dietary energy on intestinal phosphate transport and the possible underlying mechanism to explain the long-term effects of early dietary energy restriction and non-phytate phosphorus (NPP). A 2 × 3 factorial experiment, consisting of 2 energy levels and 3 NPP levels, was conducted. Broiler growth performance, intestinal morphology in 0–21 days and 22–35 days, type IIb sodium-phosphate co-transporter (NaP_i-IIb) mRNA expression, adenylate purine concentrations in the duodenum, and phosphorylated adenosine monophosphate-activated protein kinase (AMPK-α) activity in 0–21 days were determined. The following results were obtained. (1) Low dietary energy (LE) induced a high feed conversion ratio (FCR) and significantly decreased body weight gain in young broilers, but LE induced significantly higher compensatory growth in low NPP (LP) groups than in the high or medium NPP groups (HP and MP). (2) LE decreased the villus height (VH) in the intestine, and LE-HP resulted in the lowest crypt depth (CD) and the highest VH:CD ratio in the initial phase. However, in the later period, the LE-LP group showed an increased VH:CD ratio and decreased CD in the intestine. (3) LE increased ATP synthesis and decreased AMP:ATP ratio in the duodenal mucosa of chickens in 0–21 days, and LP diet increased ATP synthesis and adenylate energy charges but decreased AMP production and AMP:ATP ratio. (4) LE led to weaker AMPK phosphorylation, higher mTOR phosphorylation, and higher NaP_i-IIb mRNA expression. Thus, LE and LP in the early growth phase had significant compensatory and interactive effect on later growth and intestinal development in broilers. The effect might be relevant to energy status that LE leads to weaker AMPK phosphorylation, causing a lower inhibitory action toward mTOR phosphorylation. This series of events stimulates NaP_i-IIb mRNA expression. Our findings provide a theoretical basis and a new perspective on intestinal phosphate transport regulation, with potential applications in broiler production.

Experimental reproduction of necrotic enteritis in chickens: a review

This review discusses key factors important in successful experimental reproduction of necrotic enteritis (NE) in chickens, and how these factors can be adjusted to affect the severity of the lesions induced. The critical bacterial factor is the need to use virulent, netB-positive, strains of Clostridium perfringens; disease severity can be enhanced by using netB-positive C. perfringens strains that are also tpeL-positive, by the use of young rather than old broth cultures, and by the number of days of inoculation and the number of bacteria used. Use of cereals rich in non-starch polysaccharides can enhance disease, as does use of animal proteins. Administration of coccidia, including coccidial vaccines, combined with netB-positive C. perfringens, increases the severity of experimentally-induced NE. Dietary manipulation may be less important in coccidia-based models since the latter are so effective. Disease scoring systems and welfare considerations are discussed.

Poultry management: a useful tool for the control of necrotic enteritis in poultry

The intestinal ecosystem of poultry has been inevitably changed as a result of the ban of antimicrobial growth promoters. The re-emergence of necrotic enteritis has been the most significant threat for the poultry industry, which, in clinical form, causes high mortality and in subclinical forms, affects growth and feed conversion. It is one of the most common and economically devastating bacterial diseases in modern broiler flocks in terms of performance, welfare and mortality. Necrotic enteritis is a multi-factorial disease process, in which a number of co-factors are usually required to precipitate an outbreak of the disease. Although, Clostridium perfringens has been identified as the aetiological agent of the disease, the predisposing factors that lead to over-proliferation of C. perfringens and the subsequent progression to disease are poorly understood. Any factor that causes stress in broiler chicks could suppress the immune system and disturb the balance of the intestinal ecosystem, in such a way that the risk of a necrotic enteritis (NE) outbreak increases. Poultry management could significantly affect the pathogenesis of NE. In particular, feed restriction and coccidiosis vaccination can protect against NE, while extreme house temperature, feed mycotoxins and high stocking density predispose to NE. It becomes really important to understand the pathogenesis of the disease, as well as to clarify the interactions between husbandry, nutritional and infectious factors and the outbreak of necrotic enteritis. This is necessary and extremely important in order to develop managerial strategies at the farm level to control the incidence and severity of the disease in the post-antibiotic era.

Necrotic enteritis predisposing factors in broiler chickens

Necrotic enteritis in chickens develops as a result of infection with pathogenic strains of Clostridium perfringens and the presence of predisposing factors. Predisposing factors include elements that directly change the physical properties of the gut, either damaging the epithelial surface, inducing mucus production, or changing gut transit times; factors that disrupt the gut microbiota; and factors that alter the immune status of birds. In the past research into necrotic enteritis predisposing factors was directed by the simple hypothesis that low-level colonization of C. perfringens commonly occurred within the gut of healthy chickens and the predisposing factors lead to a proliferation of those bacteria to produce disease. More recently, with an increasing understanding of the major virulence factors of C. perfringens and the application of molecular techniques to define different clades of C. perfringens strains, it has become clear that the C. perfringens isolates commonly found in healthy chickens are generally not strains that have the potential to cause disease. Therefore, we need to re-evaluate hypotheses regarding the development of disease, the origin of disease causing isolates of C. perfringens, and the importance of interactions with other C. perfringens strains and with predisposing factors. Many predisposing factors that affect the physical and immunological characteristics of the gastrointestinal tract may also change the resident microbiota. Research directed towards defining the relative importance of each of these different actions of predisposing factors will improve the understanding of disease pathogenesis and may allow refinement of experiment disease models.