Browsing by Browse by FOR 2020 "300304 Animal protection (incl. pests and pathogens)"

Infectious laryngotracheitis, caused by the alphaherpesvirus infectious laryngotracheitis virus (ILTV), is an important disease of chickens. Partial control of this disease in meat chickens is commonly achieved by mass vaccination with live virus in drinking water. There is a need for a practical test to evaluate vaccination outcomes. For the Serva ILTV vaccine, quantitative real-time PCR (qPCR) enumeration of ILTV genome copies (GC) in flock level dust samples collected at 7-8 days post vaccination (dpv) can be used to differentiate flocks with poor and better vaccine take. This study aimed to validate this approach for A20, another widely used ILT vaccine in Australia. In four meat chicken flocks vaccinated with A20 in water using two different water stabilization times (20 or 40 min), swabs from the trachea and choanal cleft and dust samples were collected at 0, 7, 14 and 21 dpv. ILTV GC detection in swabs and dust was highest at 7 dpv and at this time ILTV GC load in dust was strongly and positively associated with vaccine take in individual birds assessed by swab samples. Choanal cleft swabs provided significantly fewer ILTV positive results than paired tracheal swab samples but the level of ILTV GC detected was similar. Water stabilization time had only minor effects on vaccination response in favour of the shorter time. Location of dust collection had no effect on viral load measured in dust samples. Dust samples collected at 0 and 7 dpv can be used to assess the vaccination status of flocks.

Australian Wool Innovation Limited (AWI) commissioned three cross-sectional surveys of sheep producers' sheep parasite control practices over a 15-year period from 2003 to 2018. The aims were to document current sheep parasite incidence and control practices, to measure change in sheep parasite control practices over time and to inform extension messages for sheep industry advisors and sheep farmers. The surveys were conducted in 2004, 2012 and 2019 measuring sheep parasite control practices in the years 2003, 2011 and 2018. The surveys focused on incidence and control of the three major sheep parasite groups; gastrointestinal nematodes, blowflies and lice. The 2003 and 2011 surveys were paper-based and the 2018 survey was accessed via a link to an online survey. This article is the first in a series of four presenting the results of the three surveys and will cover methods, demographics, production systems and general parasite management. Response rates to the surveys declined each year from the peak response rate in 2003 (n = 1365 in 2003; n = 575 in 2011 and n = 354 in 2018). Mean reported rainfall was significantly lower in 2018 (407 mm) than in 2003 (611 mm) and 2011 (650 mm). The demographics of the respondents and their production systems were largely similar between the three surveys for respondent age, median property size, income from wool and sheep meat, proportion of the property area cropped, median sheep dry sheep equivalent (DSEs), ewes as a proportion of the total flock and median cattle DSEs. Month of weaning was more likely to be in summer months for summer dominant rainfall areas and spring for intermediate and winter dominant rainfall areas. There was a marked increase in the proportion of respondents asking for an animal health history when introducing sheep to their flock from 2011 (9%) to 2018 (65%). Similarly, a greater proportion of respondents isolated introduced sheep for at least 2 weeks in 2018 (82%) compared with 2011 (19%). However, there was a decrease in the use of a quarantine lice treatment for introduced sheep from 2011 (50%) to 2018 (21%). Farmers rated themselves, other farmers or member of their staff as most important sources of information on parasite control in both 2011 and 2018. There was a significant increase in the proportion of respondents visiting the ParaBoss suite of websites from 2011 to 2018 confirming their growing importance for information delivery and decision support.

Context. The third Australian national survey on control practices for internal and external parasites of sheep, following similar surveys in 2003 and 2011.
Aims. To document current parasite control practices and attitudes, measure change and to provide a benchmark against which to assess future practices and attitudes.

Methods. An online survey emailed to 6460 sheep producers, with a paper version supplied on request. A follow up short survey was conducted to assess non-response bias. Analysis by region and key sheep enterprise.

Key results. There were 354 and 250 useable responses to the main and short surveys respectively. Mean reported rainfall of 407 mm in 2018 was 27% lower than the average for respondents and >200 mm lower than mean reported rainfall in the previous surveys. The top three methods for worm control over the past 5 years were preventative treatments (74%), preparing clean pastures by spelling paddocks (62%) and treatment on the basis of faecal worm egg count (WEC, 54%). The proportion of respondents using WEC monitoring in 2018 was 40.4%, with a mean frequency of 3.1/year, and this was unaffected by sheep class. The frequency of anthelmintic treatment for ewes and lambs and weaners was 2.1/year. Of the respondents, 36.7% had performed an anthelmintic resistance test in the previous 5 years. The most popular flystrike control methods were timing of crutching (76.4%), preventative chemical treatment (75.9%), timing of shearing (63.1%), mulesing (46.8%) and genetic selection (46.4%). Pain relief was widely used for mulesing ewes (86.6%) and wethers (90.9%). Only 17.3% used Australian Sheep Breeding Values for traits in rams. Most respondents reported 'evidence of lice' in the past 5 years (55.8%) and had treated for lice off shears (50.1%), short wool (16.6%) or long wool (6.6%), with only 26.7% having not treated at all in the period. Web-based sources of information on parasite control have become increasingly important.

Conclusions. Notable changes since the earlier surveys were high rates of pain relief when mulesing, an increase in the use of Australian Sheep Breeding Values for parasite-related traits, an increase in WEC monitoring since 2011 and an increased use of web-based resources.

Implications. Parasite control remains important for sheep producers and continues to evolve with new drugs and approaches. The surveys highlight the effectiveness of extension networks and identify where more attention is required.

Cross-sectional surveys of sheep parasite control practices in Australia were conducted in 2004, 2012 and 2019 to document parasite problems, control practices and measure change over time. This article reports the results pertaining to gastrointestinal nematode infection; comparisons between years are mostly descriptive and not based on statistical inference. There was a general increase in the use of grazing management to prepare clean pastures for sheep to control gastrointestinal nematode infections with the largest increases in the use of: cropping, long acting anthelmintics to prepare clean pastures, feeding strategies, selecting rams for resistance to nematodes, and leaving some sheep untreated. The proportion of respondents using faecal worm egg count monitoring (WEC) and the number of WEC monitors per year were similar in 2003 (weaners: 3.0 WEC/year, adult ewes: 2.6 WEC/year) and 2018 (lambs and weaners and adult ewes both 3.1 WEC/year) but lower in 2011 (lambs and weaners: 2.0 WEC/year, adult ewes: 2.9 WEC/year), whilst there was a higher number of anthelmintic treatments given in 2011 than 2003 and 2018 which were similar. There was an increase in the proportion of respondents carrying out WEC monitors themselves from 2011 (21%) to 2018 (30%) and a corresponding reduction in the use of private laboratories, government laboratories and veterinarians with regional differences in who carried out WECs. The top three anthelmintic groups used did not differ between the three survey years with macrocyclic lactones the most used followed by benzimidazoles (BZ) and levamisole (LEV) although the percentage of MLs used in 2011 and 2018 was lower than in 2003 with higher proportions of respondents using BZ and LEV groups in the latter two survey years. Moxidectin was in the most commonly used active in all survey years. There was an increase in the use of combination of anthelmintics from different groups, especially for a combination of three anthelmintics (2003: 4.4%, 2011: 19.1%, 2018: 21.5%), with lower use of single anthelmintics in 2011 (57.0%) and 2018 (55.4%) compared with 2003 (74.5%). The use of testing for anthelmintic resistance was generally low across the survey years with a lower proportion of respondents using tests in 2011 and 2018 than in 2003 (2003:48%, 2011: 29%, 2018: 37%). Time of year, results from WEC and seasonal weather condition were the most important factors when deciding when to apply anthelmintic treatment.

The objective of this study was to evaluate the effect of 2 different doses of a partially buffered formic acid product (Amasil NA; 61% formic acid, 20.5% sodium formate), and a monoglyceride blend of short- and medium-chain fatty acids (BalanGut LS P) on necrotic enteritis (NE) infected broilers in terms of performance, intestinal microbial population and shortchain fatty acids concentrations in the gastrointestinal tract. A total of 528-day-old as hatched Ross 308 broilers were allocated to 48 pens with 11 birds in each pen. Six dietary treatments applied in the study were: T1) nonsupplemented diet (Control); T2) antibiotic supplemented diets; T3) and T4) high (Starter: 0.5%; Grower and Finisher: 0.5%) and low (Starter: 0.3%; Grower and Finisher: 0.2%) dose of Amasil NA; and groups T5) and T6) high (Starter: 0.3%; Grower and Finisher: 0.2%) and low dose (Starter: 0.3%; Grower: 0.15%; Finisher: 0.075%) of (BalanGut LS P). All birds in this study were fed starter (d 0-10), grower (d 11−24) and finisher (d 25−35) diets and challenged with NE. To induce subclinical NE, oral administrations of Eimeria oocysts (d 9) followed by inoculation of Clostridium perfringens strains (d 14 and 15) were applied. Results showed that birds fed the high dose of Amasil NA, had a higher feed conversion ratio (FCR, P < 0.05) compared to the nonsupplemented group during the starter period. Antibiotic supplementation reduced FCR during the grower (P < 0.001), finisher (P < 0.05) and overall (P < 0.001) periods of the experiment. Both levels of BalanGut LS P and low levels of Amasil NA enhanced overall FCR (P < 0.05) compared to the birds in the nonsupplemented group. Compared to the nonsupplemented group, high levels of Amasil NA and low levels of BalanGut LS P improved FCR in the finisher stage (P < 0.05). On d 16, cecum digesta of birds fed with antibiotic supplemented diets showed a significantly lower number of C. perfringens (P < 0.001) compared to the nonsupplemented and high level of BalanGut LS P group. Bacillus (P < 0.01) and Ruminococcus numbers were significantly lower in the birds fed with high level of Amasil NA (P < 0.05) compared to the antibiotic supplemented diets. High doses of Amasil NA, showed the highest propionate concentration in the cecum (P < 0.001). The study suggests that supplementation of BalanGut LS P and Amasil NA at different feeding phases may achieve optimal performance improvement in broilers under NE challenge.

Due to the removal of antibiotics from animal feed, alternatives have been sought to control necrotic enteritis (NE) in broilers. The current study investigated the effects of buffered formic acid (Amasil NA) and monoglycerides of short- and medium-chain fatty acids (Balangut LS P) on the performance and gut health of broilers challenged with NE. A total of 816 as-hatched 1-d-old chicks (Cobb 500) were randomly assigned to 6 treatments with 8 replicates. Treatments were: T1) nonchallenged control; T2) NE challenged control; T3) Amasil NA (challenge plus Amasil NA, 0.3% throughout all phases); T4) Balangut LS P (challenge plus Balangut LS P, 0.5%, 0.3%, and 0.2% in the starter, grower and finisher phases, respectively; T5) Combined (challenge plus combination of T3 and T4); T6) Antibiotic (challenge plus Zn bacitracin, 0.05 % throughout all phases). Birds were orally gavaged with live Eimeria vaccine species (d 9) and with Clostridium perfringens (d 14 and 15). On d 16, birds were sampled to evaluate gut permeability, microbiota, and mRNA abundance in the jejunum. The data were analyzed in JMP software using one-way ANOVA with Tukey's test to separate means, and Kruskal-Wallis test was used for non-normally-distributed parameters. Results showed that Balangut LS P decreased (P<0.05) feed conversion ratio compared to nonchallenged ones at the end of the study. Balangut LS P reduced (P < 0.05) the level of cecal Bacteriods compared to nonchallenged group, whereas Amasil NA shifted the levels of ileal Bifidobacteria, Enterobacteriaceae, and Lactobacillus towards nonchallenged control (P > 0.05). NE challenge upregulated (P < 0.001) the expression of IL-21R, zeta chain of T cell receptor (ZAP70), and dual specificity phosphatase 4 (DUSP4) compared to nonchallenged birds, whereas Balangut LS P showed an intermediate (P > 0.05) expression pattern of these genes towards nonchallenged and antibiotic groups. In conclusion, combination of Balangut LS P and Amasil NA has the potential to be used as an additive to improve the performance and gut health of broiler chickens, especially under challenging conditions such as NE infections.

The popularity of goat farming in Lao PDR is constrained by diseases. Information on the type and prevalence of diseases in Lao goats is scattered in both the formal and informal literature, and the actual causes of common clinical syndromes are not known definitively. The situation is exacerbated by a lack of veterinary and extension services in rural areas and clear control strategies. Therefore, the work reported in this thesis was designed with four broad objectives: 1) collate the disparate data on diseases of Lao goats within the context of goat production, marketing systems and the available veterinary services in the country; 2) determine animal-level and herd-level prevalence of common clinical syndromes in Lao goats, to determine risk factors for herd-level occurrence of the most prevalent clinical syndromes; 3) determine causation for important clinical syndromes of goats in Lao PDR (eye infection, proliferative lip and facial lesions and respiratory disease) and pathogen genetic relatedness by conducting phylogenetic analysis; and 4) introduce and establish molecular diagnostic methods relevant to most common goat diseases at the Lao National Animal Health Laboratory (NAHL). Initially a review of the existing literature on goat diseases in Lao PDR was conducted to collate scattered data in the formal and informal literature. Secondly, a monthly survey based on the observations of smallholder goat farmers was conducted over 22 months to identify the prevalence of clinical syndromes and associated risk factors. Then a case-control study was conducted using PCR-based diagnostics and sequencing to identify causative infectious agents for three of the clinical syndromes in Lao goats. Lip and mouth lesions (presented on 12.2% of monthly visits), diarrhoea (9.3%) and eye lesions (9%) were the most prevalent syndromes based on farmer observations. Occurrence of any type of clinical syndrome and eye lesions were positively associated with increasing herd size and provision of salt respectively. The case-control study was used to determine the causation of eye infection, proliferative lip and facial lesions and respiratory disease, but not diarrhoea due to the unavailability of adequate number of samples. The case-control study involved 41 – 50 samples from cases and the same number from matched controls for each syndrome. The main cause of eye infections was infectious keratoconjunctivitis (pinkeye) caused by Mycoplasma conjunctivae. The main cause of proliferative lip and facial lesions was orf (contagious ecthyma, scabby mouth) caused by the orf virus. The main cause of the chronic respiratory syndrome was atypical pneumonia caused by Mycoplasma ovipneumoniae. These provided the first definitive determination of causation of three important clinical syndromes in Lao goats. The findings of this thesis have important implications for improved disease diagnosis, control and future research to support Lao goat production.

The impact of two different strains of Clostridium perfringens (Cp) (NE-18 and NE-36) on mRNA expression of genes encoding proteins involved in cell apoptosis, intestinal tight junction and production of immunoglobulins and mucin in broiler chickens was investigated. A total of 468 male Ross 308 broilers was assigned to a 2 x 3 factorial arrangement of treatments. Factors were antibiotics (+/-), necrotic enteritis (NE) and challenge (-/ NE-18/ NE-36). A significant interaction between antibiotic treatment and challenge was observed on the expression of gene CASP3 (P < 0.05); NE-18 upregulated CASP3 only in the presence of antibiotics, while NE-36 upregulated this gene regardless of antibiotic supplementation. Interestingly, both NE strains upregulated CASP8 compared to the control treatment, but NE-36 showed higher CASP8 expression than observed with the NE-18 treatment (P < 0.001). It was shown that challenge significantly downregulated OCLD (P < 0.001), ZO-1 (P < 0.05) and MUC2 (P < 0.001). CLDN1 was significantly upregulated (P < 0.001) by both the NE-36 and NE-18 challenge, but NE-36 showing comparatively greater effects compared to NE-18. A significant antibiotic × challenge interaction on MUC5ac was observed (P < 0.05), where both NE- 18 and NE-36 upregulated MUS5ac when antibiotics was applied, but only NE-36 showed such upregulation in the absence of antibiotics. IgG and IgM were significantly downregulated (P < 0.001) by both strains of Cp. These results indicate that NE challenge alters the expression of genes investigated and different strains of Cp have varying impacts, which has a direct impact on severity of the disease.

The commercial poultry industry is not well developed in Ethiopia. On the other hand, compared to many countries in Sub-Saharan Africa (e.g. Kenya, Rwanda etc.) the small-scale chicken egg production value chain is relatively well developed. With decreasing grazing land availability and increasing population size, poultry production is considered as the principal means of providing the poor with good quality animal protein, energy and minerals. Chickens are predominantly kept in village based free-range, scavenging systems with small-scale intensive chicken production contributing less than 10% of chicken products in the country. This free range, scavenging production system is not well developed since it is constrained by many factors.

Among the factors that hinder the poultry industry in Ethiopia, disease is ranked the first most important production constraint in the scavenging production system and the second in the commercial production system. The country is reported to lose half of its chicken population every year due to disease. The poor implementation of chicken health management practices in scavenging or small scale intensive production systems predisposes them to disease.

Often an acute highly fatal disease of poultry which locally known as “fengil” is blamed for chicken disease outbreaks occurring in the country. Some experts believe the “fengil” syndrome is due mostly to Newcastle Disease (ND) and blame it for most respiratory cases happening in the field. But, since multiple aetiology and complexity are characteristic features of respiratory disease of poultry, it is important to identify non-Newcastle Disease pathogens circulating in the field. There are serological and molecular reports on some important respiratory pathogens of chickens circulating in the country. To address current gaps in knowledge this thesis also has the following objectives: 1) to compare chicken health management practices and perceptions in smallholder commercial and scavenging chicken enterprises in central Ethiopia; 2) to determine the presence, and prevalence of infection with selected respiratory pathogens of chickens in central Ethiopia by serological testing; 3) to determine key risk factors for the serological presence of these pathogens in this region; and 4) to investigate the involvement of respiratory pathogens in clinical disease in the central live chicken markets of Addis Ababa and undertake comparative molecular characterisation of the detected pathogens.

To achieve the first objective a cross-sectional survey of chicken health management practices was conducted on small-scale intensive (SSI) and scavenging chicken (SCAV) enterprises in central Ethiopia. The results of this study are reported in Chapter 3. In order to achieve the second and third objectives a cross-sectional serological survey and assessment of the risk factors for seropositivity were conducted in SCAV and SSI chicken holdings in the East, West and North Shewa Zones of central Ethiopia. The fourth objectives was achieved by investigating the presence of different pathogens in the clinical respiratory cases in the central live chicken markets of Addis Ababa (Chapter 6).

Under objective 1 an important finding was that seropositivity for the pathogens was more frequent in the SCAV system than SSI system. There was also better vaccination coverage and biosecurity measures implementation in the SSI than SCAV production system. “Fengil” was the main disease condition reported by farmers in the SSI system, with non-specific digestive symptoms being most widely reported in the SCAV system. Farmers in the SCAV system farmers relied widely on use of traditional medicines whereas those in the SSI system used more modern medicines. This suggests that disease prevention and health management are improved with intensification. It was also observed that there is considerable potential to improve practices in both systems. Under objective 2 serological evidence of a high level of exposure to all five selected pathogens (avian meta-pneumo virus (aMPV), Infectious laryngotrachities (ILTV), Infectious bronchitis virus (IBV), NDV and Mycoplasma gallisepticum (Mg)) was detected, including the first report on the seroprevalence of aMPV, ILTV and IBV on the farms located in East Shewa Zone. These pathogens could potentially contribute to or complicate the fengil syndrome, which is commonly ascribed to NDV.

Exposure to multiple pathogens was common in more than half of the chickens tested. But, the role of these pathogens in the causation of respiratory disease in the field requires further investigation. Under objective 3 there were 17 risk factors found to have a significant effect on the prevalence of at least one pathogen during the univariate analysis. However only nine of these 17 risk factors were found to influence sero-positivity for one or more pathogens following multivariate analysis. Of the nine risk factors, eight of them influenced more than one disease. The most important risk factor was farmers’ duration of experience in chicken production with shorter periods associated with reduced seropositivity. Other important risk factors were increased contact with wild birds and other animals, season and location.

Therefore improved biosecurity measures aimed at minimising contact is recommended to reduce exposure to these diseases, but proper implementation is only possible in the SSI

system. Reduced disease prevalence in holdings with less experience may be indicative of owner complacency and pathogen build up in older holdings that could be addressed with targeted extension programs. The provision of dedicated housing for chickens at night should be encouraged in the SCAV system and the disease control programs could be effectively concentrated in the North Shewa zone. The pathogens associated with clinical respiratory disease are not well defined in the country. The objective 4 study of chickens with respiratory disease from the central live chicken markets in Addis Ababa revealed that all the chickens were PCR-positive for aMPV, and most of the sick chickens (17/18) were PCR positive for more than 3 pathogens. Potentially pathogenic bacteria such as Escherichia coli, Klebsiella spp., Streptococcus spp. and Staphylococcus were also isolated. This shows a high level of exposure to multiple respiratory pathogens. Disease was a major constraint in both SCAV and SSI production systems. The acute respiratory diseases which locally known as “fengil” is blamed for most disease outbreaks. Poor uptake and implementation of management practices likely contribute to the high incidence of disease. The poor chicken health management practices identified in both the SCAV and SSI production system likely contribute to the high sero-positivity of chickens for aMPV, ILTV, IBV, Mg and NDV. IN flocks not vaccinated against NDV sero-positivity of chickens for aMPV, ILTV, IBV, Mg was higher than for NDV indicating that non-NDV respiratory pathogens are circulating in the study area to a greater extent than NDV. The investigation of clinical respiratory disease in the central live chicken markets of Addis Ababa directly confirmed the presence of these pathogens in clinical cases with multiple pathogens commonly detected from individual chickens. These shows that outbreaks of clinical respiratory disease of chickens in the country may involve pathogens other than NDV and may well involve infections with multiple agents. Based on the finding of lower disease seroprevalence and higher uptake of recommended disease control practices on SSI farms it is recommended that the program of intensification of smallholder chicken production be continued. Further studies more clearly linking respiratory pathogens with clinical disease need to be carried out, and based on the findings of these, vaccines for significant respiratory pathogens should be developed or imported.

1. The aim of this study was to examine the effect of yeast cell wall (YCW) on performance and physiological responses of broiler chickens under subclinical necrotic enteritis challenge.

2. Six treatments in a 2 × 3 factorial arrangement (non-challenged or challenged plus no supplement, YCW or antibiotics (AB)) was used. Each treatment was replicated eight times with 12 birds per replicate. The treatments included: (1) Positive control (PC; no additive, not challenged); (2) Negative control (NC; no additive, with challenge); (3) YCWN = yeast cell wall (2.0 g/kg diet, not challenged; (4) YCWC = yeast cell wall (2.0 g/kg diet, challenged); (5) ABN = zinc bacitracin 50 ppm + Salinomycin 60 ppm, not challenged); (6) ABC = zinc bacitracin 50 ppm + Salinomycin 60 ppm, challenged).

3. Eimeria challenge at 9 d of age did not affect feed intake (FI), body weight gain (BWG), FCR or liveability at 10 d. The BWG and FCR at 10 d were greater (P < 0.05) in birds fed YCW or AB (AB) diets relative to the PC or NC groups. On 24 and 35 d, FI, BWG, FCR and flock uniformity (28 d) were greater (P < 0.05) in the challenged groups fed YCW or AB diets compared to NC group.

4. Supplementation with YCW ameliorated the negative effects of NE on liver, spleen and bursa weight of birds.

5. Necrotic enteritis challenge decreased (P < 0.05) caecal Lactobacillus and Bifidobacterium spp. counts, and increased ileum lesion score and caecal Clostridium perfirngens counts. This was reversed by the addition of either YCW or AB.

6. Supplementation with YCW and AB resulted to a greater (P < 0.05) dressing percentage and meat yield (35 d).

7. The results indicated that YCW plays a vital role in improving the physiological response and performance of broiler chickens under subclinical necrotic enteritis challenge.

Necrotic enteritis (NE), mainly caused by the gram-positive anaerobic bacterium Clostridium perfringens (Cp), is an enteric disease with great economic impact for the broiler industry. The prohibition of in-feed antibiotics has resulted in an increase in NE incidences globally. The severity of the disease in broilers depends on many factors. However, the type of Cp strains used plays a critical role. This study examined the impact of two Cp strains, i.e. NE18 and NE36, on performance, lesion score and gut permeability of broilers. Ross 308 broilers (n = 468) were assigned to a 2 × 3 factorial design (Feed: With/Without antibiotic) × (Challenge: No / NE18/ NE36). Oral administrations of Eimeria species (d9) and two stains of Cp (d14) were used to induce NE in the challenged groups. On d16 two birds from each pen were inoculated with FITC-d and serum samples were subsequently obtained for leaky gut evaluation. FITC-d amount was measured using a microplate reader (Synergy HT, Multi-mode microplate reader, BioTek Instruments, Inc., VT, USA). Broiler performance (Feed Intake, FI; weight gain, WG; and feed conversion ratio, FCR) was analysed for d0-24 period. Intestinal lesion scoring and gut permeability were measured at d16. Weight gain in the challenged group was significantly lower (P < 0.001) compared to the unchallenged birds at d24. Challenge also reduced the FI significantly (P < 0.001). FCR was significantly higher in the groups challenged with NE18 (P < 0.001) and NE36 (P < 0.001) compared to nonchallenged birds. Antibiotic diets significantly decreased FCR (P < 0.05) and increased WG (P < 0.05) in all groups. Birds challenged with NE36 showed higher FCR (P < 0.001) compared to the birds challenged with NE18 indicating a more severe impact of the NE36 than NE18. Ileal lesion scores and gut permeability were not significantly different between the two strains, but numerically higher number of lesions and gut permeability were observed in birds challenged with NE36. Supplementation with antibiotics reduced (P < 0.05) gut permeability in the birds of all groups. The findings of this study indicate that the severity of necrotic enteritis disease in challenge model can be modulated by the use of different Cp strains.

The primary cause of necrotic enteritis (NE) disease in chickens is the NetB-positive Clostridium perfringens bacterium. Many factors are known to affect the severity of NE in the challenge models of broiler chickens, and one of these factors is the virulence of C. perfringens strain. This study was conducted to evaluate the effect of 2 pathogenic C. perfringens strains in a NE challenge model on gut health and mRNA expression of genes encoding apoptosis, tight junction, immunity, and nutrient transporters in broilers. Day-old Ross-308 male broilers (n = 468) were allocated in a 2 × 3 factorial arrangement of treatments with in-feed antibiotics (no or yes) and challenge (Non, C. perfringens strain NE18, and C. perfringens strain NE36) as the factors. The birds in the challenged groups were inoculated with Eimeria species on day 9 and with a fresh suspension of C. perfringens NE18 or NE36 on day 14 and 15. Sample collection was performed on 2 birds of each pen on day 16. Necrotic enteritis challenge, impaired feed conversion ratio during day 0 to 16 compared with the control group where the effect of the NE36 challenge was more severe than that with NE18 (P < 0.001). The mRNA expression of mucin-2, immunoglobulin-G, occludin (P < 0.001), and tight junction protein-1 (P < 0.05) genes were downregulated in both challenged groups compared with the nonchallenged counterparts. Antibiotic supplementation, on the other hand, increased weight gain, and feed intake in all challenged birds (P < 0.01), but upregulated mucin-5ac and alanine, serine, cysteine, and threonine transporter-1 (P < 0.05) only in the NE18 challenged birds. The challenge with NE36 significantly upregulated caspase-8 and claudin-1 (P < 0.001), but downregulated glucose transporter-2 (P < 0.001) compared with the NE18 challenge. These results suggest that NE challenge is detrimental to the performance of broilers through compromised intestinal health, and different C. perfringens strains can affect the severity of the disease through modulating the expression of intestinal genes encoding proteins responsible for apoptosis, gut integrity, immunity, mucus production, and nutrient transporters.

Necrotic enteritis (NE) is a major concern for the poultry industry worldwide as it causes reduced production and increased mortality, resulting in an estimated annual economic loss of US$6 billion (Wade and Keyburn, 2015). It is widely accepted that feed composition strongly influences the gut environment, consequently affecting the prevalence and severity of necrotic enteritis (Branton et al., 1997). Cereal grains such as wheat, barley and rye contain high levels of non-starch polysaccharides (NSPs) that have a direct negative impact on nutrient utilization. Insoluble NSPs can act as a physical barrier to enzymes. Soluble NSPs increase digesta viscosity, which may affect intestinal barrier function. Compromised barrier function results in translocation of luminal pathogens and a non-specific inflammatory response (Tellez et al., 2014).