Varying starch to fat ratios in pelleted diets: II. Effects on intestinal histomorphometry, Clostridium perfringens and short-chain fatty acids in Eimeria-challenged broiler chickens.

1. The hypothesis behind the study was that a high dietary starch level (HS) would lead to impaired gut health compared to a low-starch diet (LS) in Eimeria-challenged broilers. The effects of two diets with different starch to fat ratios on intestinal histomorphometry, Clostridium perfringens counts and toxin profile, necrotic enteritis prevalence and abundance of short-chain fatty acids (SCFAs) were examined. 2. A total of 1,920 one-day-old Ross 308 broiler chickens were fed one of two isocaloric diets formulated either with high (32:1) or low (2:1) starch to fat ratios from d 10 to 29 of age. Each treatment group had 12 pen replicates containing 80 broilers each. On d 17, the chickens were challenged with Eimeria vaccine strains. Samples were collected on d 16, 21-23 and 29. 3. Whereas villus length increased gradually throughout the study in the HS group, a peak level was reached on d 21-23 in the LS group. On d 29, the HS group had significantly longer villi than the LS group. 4. Caecal SCFA concentrations were higher in the HS group compared to the LS group on d 16. In both groups, the SCFA level peaked on d 21-23, with the most pronounced increase seen in the LS group. 5. The C. perfringens netB:cpa ratio increased from d 16 to 29 in the HS group. C. perfringens counts and necrotic enteritis prevalence were similar between the two groups. 6. Diet affected the dynamics of small intestinal villus length and caecal SCFA abundance. These findings suggest that structural remodelling of the small intestine is an adaptation to different dietary starch levels, and that caecal SCFA abundance is associated with the availability of substrate for the microbiota in the posterior intestinal segments. Chickens adapted to higher levels of dietary starch might be more robust against Eimeria infections due to increased mucosal surface area. Studies with other dietary starch sources are required to clarify the impact of dietary starch levels on intestinal health in Eimeria-challenged broilers.

Varying starch to fat ratios in pelleted diets: I. Effects on nutrient digestibility and production performance in Eimeria-challenged broiler chickens.

1. The hypothesis was that a diet with a high starch to fat ratio (HS) impairs nutrient digestibility and growth performance, as compared to a diet with a low starch to fat ratio (LS) in Eimeria-challenged broilers. From days 10 to 29, 12 replicate pens of birds were given isocaloric and isonitrogenous steam-pelleted diets with either HS or LS, by replacing the wheat starch in one diet by a mixture of rapeseed oil and inert sand in the other. On d 17, a 10-fold dose of live vaccine strains of Eimeria spp. was administered via drinking water. Ileal samples were collected on days 16 and 29. 2. Starch content in the ileum tended to be higher on d 16 and was significantly higher on d 29 in the HS group. 3. The HS diet did not induce exceedingly high levels of starch in the ileum, suggesting there was no starch overload in the gut. Ileal starch digestibility was improved with increasing dietary starch level from 23% to 45%. This demonstrated the capacity of the broiler chicken to digest high levels of starch regardless of Eimeria spp. infection. Ileal energy digestibility was not affected by the treatments. 4. Weight gain did not differ between treatments; however, birds fed the LS diet were less efficient in feed conversion as compared to those fed the HS diet. 5. The use of isolated starch and the unintended higher extent of starch gelatinisation in the HS diet may have contributed to the higher starch digestibility in birds given the HS diet. Thus, the hypothesis that high ratios of starch to fat in pelleted diets may impair starch digestibility and production performance in Eimeria-challenged broiler chickens was not verified. Further work is required to clarify this research question, taking into consideration the physical form of starch source and the potentially confounding role of feed processing on starch availability.

Ectopic epithelial cell clusters in salmonid intestine are associated with inflammation.

An epizootic incidence of intestinal adenocarcinomas was reported in brood fish of Atlantic salmon (Salmo salar L.) in 2009. The condition was associated with a specific diet inducing enteritis and morphological changes. Here, two field trials of fish up to slaughter size were initiated. In Trial 1, two different feed recipes were used. Feed I was predominantly based on marine ingredients, whereas plant ingredients were limited to soy protein concentrate and wheat. Feed II was lower in fishmeal and without soya protein, which was substituted with plant proteins from other sources. In Trial 2, a commercial feed (Feed III) was included. No macroscopic tumours were observed in 300 fish (Trial 1). At the end of both trials, samples from five different segments of the gastrointestinal tract of a total of 39 fish were investigated with morphological methods. Here, we show the presence of ectopic proliferating epithelial cells only occurring in inflamed intestine and predominantly in the second segment of the mid-intestine. Presence of ectopic epithelial cells in submucosal inflammatory foci may indicate early stages in tumorigenesis, but other possibilities such as proliferative enteric disorders cannot be excluded. Together with inflammation, carcinogenesis should be a focus of investigation in future feed trials.

Immersion challenge with low and highly virulent infectious salmon anaemia virus reveals different pathogenesis in Atlantic salmon, Salmo salar L.

The salmonid orthomyxovirus infectious salmon anaemia virus (ISAV) causes disease of varying severity in farmed Atlantic salmon, Salmo salar L. Field observations suggest that host factors, the environment and differences between ISAV strains attribute to the large variation in disease progression. Variation in host mortality and dissemination of ISAV isolates with high and low virulence (based on a previously published injection challenge) were investigated using immersion challenge. Virus dissemination was determined using real-time PCR and immunohistochemistry in several organs, including blood. Surprisingly, the low virulent virus (LVI) replicated and produced nucleoprotein at earlier time points post-infection compared to the virus of high virulence (HVI). This was particularly noticeable in the gills as indicated by different viral load profiles. However, the HVI reached a higher maximum viral load in all tested organs and full blood. This was associated with a higher mortality of 100% as compared to 20% in the LVI group by day 23 post-infection. Immersion challenge represented a more natural infection method and suggested that specific entry routes into the fish may be of key importance between ISAV strains. The results suggest that a difference in virulence is important for variations in virus dissemination and pathogenesis (disease development).

Non-soluble fibres and narasin reduce spontaneous gizzard erosion and ulceration in broiler chickens.

The prevalence and severity of gizzard erosion and ulceration syndrome (GEU) in broilers is affected by a number of predisposing and preventive factors. Two broiler experiments with almost identical basal diets were conducted to investigate the effect of dietary oat hulls, access to litter and the antimicrobial compound narasin on GEU. The effects on particle size of duodenal digesta, ileal starch concentration, caecal Clostridium perfringens counts, necrotic enteritis and production performance were also examined. Oat hulls reduced GEU severity and starch levels in the ileum in both experiments. Access to litter reduced GEU scores when oat hulls were included in the feed. Access to litter also improved feed efficiency and reduced C. perfringens counts. Narasin reduced GEU severity when the feed was supplemented with oat hulls. Oat hulls were associated with improved feed efficiency in Experiment 1 and impaired feed efficiency in Experiment 2. The inconsistent effect of oat hulls on production performance appeared to be related to an association between oat hulls and high C. perfringens counts in Experiment 2; an association that was absent in Experiment 1. In general, oat hulls interacted with litter access and narasin in exerting a positive effect on gizzard health. However, the association between oat hulls and necrotic enteritis detected in Experiment 2 suggests that the positive effect of oat hulls on GEU occasionally may be outweighed by a negative effect on gut health. In conclusion, our findings demonstrate that the severity of GEU in broilers was influenced by non-soluble fibres and narasin.

Prevention of intestinal Campylobacter jejuni colonization in broilers by combinations of in-feed organic acids.

AIM: We have tested the effect of various combinations of formic acid and sorbate on Campylobacter jejuni colonization in broiler chickens to reduce the colonization of this zoonotic pathogen in broiler chicken flocks. METHODS AND RESULTS: Chickens were offered feed supplemented with different concentrations and combinations of formic acid and/or potassium sorbate. We found little or no effect on the Camp. jejuni colonization levels in chickens that were given feed supplemented with formic acid alone. A combination of 1.5% formic acid and 0.1% sorbate reduced the colonization of Camp. jejuni significantly, while a concentration of 2.0% formic acid in combination with 0.1% sorbate prevented Camp. jejuni colonization in chickens. This inhibition was replicated in two independent trials with a combination of three different Camp. jejuni strains. CONCLUSIONS: Our results show a novel and promising intervention strategy to reduce the incidence of Camp. jejuni in poultry products and to obtain safer food. SIGNIFICANCE AND IMPACT OF THE STUDY: To ensure food safety, a reduction of the carcass contamination with Camp. jejuni through reduced colonization of this pathogen in broiler chicken flocks is important. A range of organic acids as additives in feed and drinking water have already been evaluated for this purpose. However, no studies have yet shown a complete inhibition of Camp. jejuni colonization in broiler chickens.

A field study of naturally occurring specific antibodies against Clostridium perfringens alpha toxin in Norwegian broiler flocks.

Necrotic enteritis (NE), a disease associated with high numbers of the intestinal bacterium Clostridium perfringens, is common in intensive broiler production. Antimicrobial feed additives may control the disease, but their use is now being questioned in many countries. A field study was undertaken at the end of 1997 to study the level of naturally occurring specific humoral immunity against phospholipase C (PLC; C perfringens alpha toxin) in Norwegian broiler flocks. Blood samples were collected at hatch from 61 study flocks, and the sampling was repeated for 56 of the same flocks at processing. The level of specific antibodies against PLC was analyzed in an enzyme-linked immunosorbent assay (ELISA) test. Data on production performance and weekly mortality were recorded. The relationship between the age of the hens and the level of specific maternal antibodies in the progenies was studied. The association between the level of the maternal antibodies and the production performance, including mortality, was analyzed. The level of specific antibodies against PLC in day-old broiler flocks was relatively high and varied considerably compared with the levels in the broilers at processing. The progenies from the oldest hens had significantly higher levels of specific antibodies than the chicks from younger hens. No outbreak of NE occurred during the study period, making it impossible to analyze the association between naturally occurring specific immunity against PLC and the occurrence of the disease. However, the results showed that the flocks with high titers of specific maternal antibodies against PLC had lower mortality during the production period than flocks with low titers.

Reduced incidence of Clostridium perfringens-associated lesions and improved performance in broiler chickens treated with normal intestinal bacteria from adult fowl.

The dosing of young chicks with cultures of normal gut flora has been termed "competitive exclusion" (CE). This study was undertaken to examine, under field conditions, the effect of CE treatment on counts of intestinal Clostridium perfringens (CP) and on the occurrence of CP-associated disease in broiler chickens. A farm having recurrent CP-associated health problems was selected as study site. The study comprised four broiler houses, with one treated and one untreated flock per house. Treated birds were sprayed with the CE product Broilact upon arrival at the farm. All flocks were offered feed containing the ionophorous anticoccidial agent narasin. The feed did not contain growth promoters. Treatment was associated with positive but statistically nonsignificant effects on gut health. Delayed intestinal proliferation of CP and delayed appearance of CP-associated gut lesions were found in CE-treated flocks. This delay was associated with improved production performance at slaughter.

Severely impaired production performance in broiler flocks with high incidence of Clostridium perfringens-associated hepatitis.

Historical meat inspection data and production performance data collected from a large poultry processing plant in Norway were used to study the association between Clostridium perfringens infection and production performance in commercial broiler flocks. The study period was limited to the first 2.5 years after withdrawal of the in-feed antibiotic avoparcin, when necrotic enteritis was frequently seen. High levels of C. perfringens-associated hepatitis at slaughter were used as an indicator of C.perfringens infection. The contribution margins were 25 to 43% lower from flocks with high levels of C. perfringens-associated hepatitis than those with low levels. Impaired feed conversion ratio and reduced bodyweight at slaughter were major causes of the losses, while condemnations per se contributed to one-fifth of the losses in profit. Incidence of liver lesions showed remarkable variation throughout the study period, and there was considerable difference in frequency of liver lesions between farms.

Necrotic enteritis challenge models with broiler chickens raised on litter: evaluation of preconditions, Clostridium perfringens strains and outcome variables.

The effect of Clostridium perfringens challenge, number of challenge days, and pre-challenge antibiotic treatment on the induction of necrotic enteritis in broiler chickens raised on litter was studied, and the relationship between bacterial counts and frequency of gut lesions was evaluated. Specific intestinal lesions in randomly selected birds were present despite a lack of disease-specific mortality. Challenge, number of challenge days and frequency of lesions were associated with median counts of C. perfringens. The effect of pre-challenge C. perfringens counts and antibiotics cannot be evaluated unless procedures for the control of pre-challenge infection and methods for the differentiation between wild-type and challenge strains are established.

Liver lesions seen at slaughter as an indicator of necrotic enteritis in broiler flocks.

Historical data of necrotic enteritis incidence and carcass condemnations owing to liver lesions in south-eastern Norway during 1978-1998 revealed covariance in the occurrence of the two variables. In histological examination during the first half of 1998, 33 of 45 sampled carcasses condemned owing to liver lesions showed histopathological changes consistent with earlier described Clostridium perfringens-associated hepatitis. The results suggest that the occurrence of necrotic enteritis in broiler flocks may be monitored by using meat inspection data on liver lesions.

A longitudinal field study of mortality and Marek's disease in Norwegian and imported white Leghorns.

High mortality during the first part of the laying period was observed in Norwegian White Leghorns during the period 1988-1992. A longitudinal field study with repeated measurement of cumulative mortality was undertaken in the period from January 1994 to January 1996 to investigate (1) the mortality and susceptibility to Marek's disease (MD) in the Norwegian strain (NB41) compared to two imported layers, (2) the effect of MD on the total cumulative mortality in the period from 16 to 32 weeks of age in White Leghorn flocks, and (3) the effect of MD as judged by repeated measurement of cumulative mortality in the same period. All five layer hatcheries and 67% of the pullet-rearing farms in Norway participated in the field study. The egg-production farms were sampled by convenience. Recordings for the whole period were completed for 169 flocks in 101 farms. The statistical analyses were performed using both a general fixed-effects linear model and a mixed model with repeated measurements, with total flock-level cumulative mortality and flock-level cumulative mortality in four-week intervals as outcome variables, respectively. The overall cumulative flock-level incidence of MD was 12% (24% and 8% in NB41 and Lohmann White, respectively). MD was not recorded in any of the Shaver White flocks. A significant difference (p < 0.001) was found in (1) total cumulative mortality: 8.2% in the NB41 and 5.0% in the imported layers, and (2) 'interval-specific' cumulative mortality: 0.36% in the NB41 and 0.15% in the imported birds. A strong relationship was also demonstrated between MD and repeated measurements of 'interval-specific' cumulative mortality (p < 0.001) but not when cumulative mortality was used as an overall measure for the whole laying period (p = 0.11). The results from the repeated-measures analysis also indicated a stronger effect of MD on flock-level 'interval-specific' cumulative mortality in the NB41 than in the imported hens. The different cumulative mortality and susceptibility to MD observed in the NB41, compared to the imported hens, shows that the farmers will be able to reduce their losses by replacing the NB41 strain with one of the imported strains.

Clostridium perfringens necrotizing enteritis of the fowl: a light microscopic, immunohistochemical and ultrastructural study of spontaneous disease.

Moderate lesions of spontaneous necrotic enteritis were investigated by light microscopy, immunoperoxidase staining, and electron microscopy. Concurrent coccidial infection was detected in the intestinal mucosa of the majority of diseased birds. Electron microscopy of intestinal epithelium revealed vesiculation and blebbing of the luminal cell membrane, as well as degenerative changes of cytoplasmic organelles. Using immunoperoxidase staining, Clostridium perfringens was identified and shown to constitute the majority of organisms in necrotic tissues, whereas bacteria were never seen in viable tissue. Thus, Clostridium perfringens always appeared to be present in the lesions and to act locally, causing a coagulative type of necrosis. The observed vesiculation of epithelial cell membranes indicates that the hydrolysis of membrane components by bacterial toxins could be important in the pathogenesis of necrotic enteritis.

No association found between the ascites syndrome in broilers and feeding of oats contaminated with deoxynivalenol up to thirty-five days of age.

This study investigated the possible effects of feeding broilers oats that were naturally contaminated with deoxynivalenol (DON) on development of the ascites syndrome. Four groups of 240 birds were fed complete feed mixtures with graded amounts of contaminated oats giving from .1 (control) to 3.4 mg DON/kg feed. The broiler chickens were 1 d old at start of trial and were slaughtered at Day 35. Performance and carcass quality were not affected by the mycotoxin in the diets. No clinical signs of ascites or occurrence of other treatment-related lesions were detected.

Barley inclusion and avoparcin supplementation in broiler diets. 2. Clinical, pathological, and bacteriological findings in a mild form of necrotic enteritis.

The clinical, pathological, and bacteriological findings of a mild form of necrotic enteritis (NE) in broiler chickens are presented. The term subclinical NE (SNE) is proposed for this condition. A diagnosis of SNE was based on the detection of macroscopically visible, focal necrotic lesions in the small intestinal mucosa. The ileal gut contents from SNE birds yielded increased numbers of Clostridium perfringens and reduced numbers of coliform bacteria. Reduced numbers of lactobacilli and streptococci were detected in birds from SNE pens and coccidial oocysts were not found in the rectal contents of SNE birds. Statistical analyses showed strong correlations between SNE and increased feed conversion ratio and retarded growth rate. An increased occurrence of SNE was observed in birds on a diet containing a large amount of barley.

Barley inclusion and avoparcin supplementation in broiler diets. 1. Effect on small intestinal bacterial flora and performance.

Diets based on barley or corn without avoparcin supplementation were associated with high counts of Clostridium perfringens in the contents of the small intestine of the birds at the age of 2 to 4 wk. The weight gain of birds younger than 2 wk and the body weight of 4-wk-old birds were significantly lower, and the feed conversion ratio at slaughter was significantly higher, in birds on barley diets than in birds on corn diets. The frequency of birds with sticky droppings on Day 21 was significantly higher for barley diets. The number of C. perfringens, and the feed conversion ratio at slaughter were significantly lower but the number of coliform bacteria, weight gain during the 3rd wk, and body weight of 4-wk-old chickens were significantly higher when the diets were supplemented with 7.5 mg avoparcin/kg feed. The effect of avoparcin on the feed conversion ratio was statistically significant only on a barley diet.