The role of supplemental glycine on broilers performance under subclinical necrotic enteritis
Coccidial co-infection, dietary inclusion of viscous grains and ingredients of animal origin protein are considered important predisposing factors for onset of necrotic enteritis (NE). High dietary glycine levels has been shown to increase the intestinal 'C. perfringens' population in broilers (Dahiya et al. 2005). As the causative agent for NE, the spore germination of 'C. perfringens' can be activated by the spore cortex-lytic enzyme (SCLE) coded by SleC thus to cause gastrointestinal disease. Investigations have shown that glycine forms a conjugated compound with bile salts playing a critical role in Clostridial germination (Sorg and Sonenshein 2008). This compound is recognized by the germinant receptor, CspC and is responsible for cleaving the N-terminal propeptide of SleC, expressing mature SCLE to activate its hydrolase activity. The current study assessed the impact of a high dietary glycine inclusion on performance of broilers under subclinical necrotic enteritis challenge.
Intermittent lighting improves resilience of broilers during the peak phase of sub-clinical necrotic enteritis infection
Necrotic enteritis, either in its clinical or sub-clinical form is known to cause massive economic losses in the broiler chicken industry. Currently, the use of in-feed antibiotics as growth promoters is discouraged. Therefore, mechanisms to control NE through diet include reduction of digesta viscosity, promotion of lower pH in the gastrointestinal tract (GIT) through acidification of feed, production of short-chain fatty acids and overall stimulation of beneficial bacteria growth. Intermittent lighting programs increase feed retention in the crop and reduce pH in the foregut compartments in comparison with standard commercial lighting programs and therefore may be a valuable, yet underexploited, barrier to prevent the invasion of the GIT by pathogens. In this experiment, a 2 × 2 factorial arrangement of treatments was employed in a randomized design to investigate whether intermittent lighting would increase broiler resilience to sub-clinical necrotic enteritis. A total of 390 Cobb 500 same-hatch, mixed sex, day-old chicks were assigned to 30 floor pens to test the effect of 2 factors, namely, lighting schedule (continuous, 18L:6D vs. intermittent, 1L:3D:1L:3D:1L:3D:1L:3D:2L:6D) and a subclinical necrotic enteritis challenge (challenge vs. no challenge). Challenged birds had lower feed intake and weight gain and poorer feed conversion ratio (FCR; P < 0.005). Intermittent lighting reduced feed intake (P < 0.05) without compromising final body weight gain. During the peak phase of 'Clostridium perfringens' Type A infection, the negative impact of the disease challenge on feed efficiency was lower for animals under intermittent lighting than for those under a 18L:6D schedule (2-way interaction, P < 0.005). Thus, in flocks that are raised under antibiotic-free production systems, intermittent lighting programs applied at least during the critical period for necrotic enteritis risks, i.e., d 18-24, may be a practical, non-medicated way to increase resilience of broilers to this disease.
Effect of different enzyme preparations on in vitro viscosity of wheat
Wheat is a common raw material in Australian broiler diets because of its high starch and protein content. However, the main concern with wheat is the presence of soluble non starch polysaccharides (NSPs), especially arabinoxylans. Arabinoxylans may account for up to 61 g/kg of wheat dry matter (Choct and Annison, 1990). These NSPs are difficult to digest and may cause digesta to become viscous thereby reducing nutrient digestion and absorption. Many NSP degrading enzyme products are commercially available and are used in the poultry feed industry. This study was undertaken to compare the effect of different enzymes preparations on in vitro viscosity of different wheat varieties.
An early feeding regime and a high-density amino acid diet on growth performance of broilers under subclinical necrotic enteritis challenge
Broilers that have early access to feed have been shown to have enhanced immune system and gut development and heightened resilience against necrotic enteritis (NE). This study examined the effect of early feeding a high amino acid density diet on performance of broilers under a sub-clinical NE challenge model. Ross 308 broilers (n = 576) were assigned to a 2 x 2 x 2 factorial design with 2 feeding regimes (feed access either within 6 h post-hatch or after 48 h post-hatch), 2 diets (control diet or the control diet with an additional 10% digestible amino acids [HAA]) and either presence or absence of NE challenge. Oral administrations of 'Eimeria' species (d 9) and a field strain of 'Clostridium perfringens' (d 14) were used to induce NE. Broiler performance was analysed at d 13, 23, 30 and 35. Intestinal lesion score and bacterial count were analysed on d 16. The NE challenge reduced overall bird performance and induced severe intestinal lesions, without causing notable mortality. At d 23 bird weight was significantly lower (P < 0.001) in the challenged birds compared with the unchallenged birds, but by d 30 the challenged birds had recovered and challenge no longer had an impact on bird performance. Birds fed the HAA diet had greater body weight by d 35 and heightened 'Lactobacillus' content in the ileum at d 16 (P < 0.05). Birds that were fed the HAA diet after a period of fasting performed better in terms of feed conversion ratio (FCR) under challenge. The findings from this study suggest there are beneficial effects of feeding high amino acid diets to birds in response to external stresses, such as post-hatch fasting and subclinical NE.
Impact of a Macleaya cordata-derived alkaloid extract on necrotic enteritis in broilers
Necrotic enteritis (NE) causes significant economic losses in the broiler chicken industry, especially in birds raised without in-feed antibiotics. A standardized blend of plant-derived isoquinoline alkaloids (IQA) derived from Macleaya cordata has shown to have anti-inflammatory potency and promoted animal productivity. This study investigated the effects of IQA supplementation on broiler chickens under NE challenge. A 2 × 2 factorial arrangement of treatments was employed with factors: NE challenge (no or yes), and additives (no additive or IQA at 0.15 g/kg) in starter, grower, and finisher diets. Birds were challenged with Eimeria spp. on d 9 and 10⁸ to 10⁹Clostridium perfringens on d 14. Each treatment had 7 replicate floor pens with 17 birds each. NE challenge negatively affected growth performance, livability, and carcass traits. Regardless of challenge, IQA increased feed intake and gain on d 24 (P < 0.05) and 35 (P < 0.01) and improved FCR (P < 0.05), flock uniformity (P < 0.01) and breast meat yield (P < 0.001) on d 35. Supplementation of IQA also reduced lesions in the duodenum (P < 0.05), jejunum (P < 0.001), and ileum (P < 0.001). This study suggests that IQA may protect broilers from NE indicating its role as a promising antibiotic alternative.
Real-Time PCR Assay for 'Clostridium perfringens' in Broiler Chickens in a Challenge Model of Necrotic Enteritis
We compared ileal 'Clostridium perfringens' quantification results produced by real-time PCR and culture-based methods in broiler chickens in a challenge model of necrotic enteritis. Assessment of the relative standard deviations (RSDs) revealed that the real-time PCR assay generated a smaller standard deviation and thus was more precise than the culture-based method. Linear regression analysis indicated that the bacterial counts of these two methods were highly correlated (R2 = 0.845). We suggest that real-time PCR could be a replacement of the culture method for quantifying 'C. perfringens' in the intestinal tracts of broiler chickens.
The effect of insoluble fibre and intermittent feeding on gizzard development, gut motility, and performance in broiler chickens
A trial was conducted to test the following hypothesis; broiler exposure to coarse insoluble fibre in the diet or litter will result in enhanced gizzard function and performance, improved adaptability to an intermittent feeding program and an increase in the occurrence of reverse peristalsis. Ross 308 broiler chickens were either intermittent or ad libitum fed a basal diet, a basal diet diluted with 15 % coarse hulls (barley and oats) or a basal diet diluted with 15 % finely ground hulls in a 2x3-factorial experiment (n = 17 birds/treatment). From 18 days of age, the birds were transferred to individual cages. Birds on intermittent feeding had restricted access to feed from 11 days of age. From 18 days of age, the restrictive feeding program consisted of four one-hour meals and one two-hour meal per day. AME value and faecal starch digestibility were determined by quantitative collection of excreta. At 31 and 32 days of age, birds were inoculated with CrEDTA via the cloaca. Weights were recorded and digesta samples collected from the gizzard, duodenum, jejunum, and ileum. There was no interaction between diet and feeding regime for any of the parameters measured. The addition of coarse oat and barley hulls resulted in birds with fuller, heavier gizzards (p < 0.001). Intermittently fed birds raised on the coarse hull diet exhibited an improved starch digestibility compared to birds not exposed to hulls (p < 0.001). The presence of chromium in all intestinal tract sections of birds from the six treatment groups, confirms that reflux occurs along the entire length of the gastro intestinal tract, irrespective of insoluble fiber content of the feed or feeding regime.
The Effect of a Plant Alkaloid Supplement on Performance of Broilers Under Necrotic Enteritis
Necrotic enteritis (NE) in broilers is caused by Clostridium perfringens. The disease may result in significant economic loss and is currently controlled in Australia by feeding low doses of antibiotic growth promotors (AGP). Alternatives to AGP have been sought since the EU ban of AGP use in livestock. The phytogenic feed additive (Sangrovit® Extra) based on quaternary benzophenanthridine and protopine alkaloids (QBA+PA) shows potential as an AGP alternative that has been reported to be anti-inflammatory, anti-microbial and immunomodulating (Khadem et al., 2014).
A Multifactorial Analysis of the Extent to Which 'Eimeria' and Fishmeal Predispose Broiler Chickens to Necrotic Enteritis
Necrotic enteritis (NE) is an important infectious disease in chickens. Predisposing factors play critical roles both in disease outbreaks in the field and in models for experimental induction of disease. Systematic manipulation and study of predisposing factors help to optimize methods for the experimental reproduction of disease. The nature of such factors may play a confounding role in challenge models and, therefore, warrant investigation to determine their importance in industry-relevant NE reproduction models. In the present study, we examined the roles of dietary fishmeal inclusion, Eimeria inoculation (E), and 'Clostridium perfringens' challenge (C) on broiler growth performance and induction of NE infection. The results showed that E, preceding C, greatly increased the severity of NE induced in broiler chickens, but fishmeal addition played only a marginal role in the challenge model. Bird performance was significantly affected by all three factors during the 35-day experimental period. Fishmeal increased body weight, but statistically significant effects of fishmeal were not observed on feed conversion ratio (FCR) and feed intake. Both 'Eimeria' and 'C. perfringens' significantly reduced body weight gain and feed intake. E but not C led to significantly poorer FCR. These findings indicate that dietary fishmeal may be removed from the model to allow the performance results of challenged chicks to be equivalent to the performance of chicks in the field. In conclusion, the present study demonstrates that an NE challenge model without fishmeal is valid and removes bird performance bias in the model introduced by feeding high fishmeal diets, refining the model to facilitate the yield of more commercially relevant results.
Natural plant extracts and prebiotic compounds as alternatives to antibiotics in broiler chicken diets in a necrotic enteritis challenge model
An experiment was conducted to determine the effects of two different water-soluble carbohydrate extracts (renga renga lily extract and 'Acacia' extract), and two commercially available prebiotic compounds, Fibregum and Raftifeed-IPE, on the performance of broiler chickens subjected to a necrotic enteritis (NE) challenge model. These treatments were compared with negative control and a positive (Zn-bacitracin) control treatments. An overall 8.8% NE-related mortality was recorded, with mean jejunal and ileal lesion scores in dead birds ranging from 3.03 to 3.90 in all challenged groups except the positive control groups. NE-specific deaths or clinical abnormalities were not observed with unchallenged control and positive control groups. At 7 days post-challenge, the concentration of specific IgY antibodies against the α-toxin of 'Clostridium perfringens' in the serum was lower ('P' < 0.05) in birds fed the positive control and Fibregum-supplemented diets than in the negative control group. However, birds fed Fibregum had increased ('P' < 0.05) IgM concentration compared with those fed 'Acacia' extract and lily extract. The Fibregum-fed group also had higher ('P' < 0.05) IgA concentrations in serum than did the positive-control and lily extract-supplemented groups at 14 days but this effect did not persist to 21 days. The results from the present study demonstrated that supplementation with water-soluble carbohydrates from two plant sources was not effective in controlling NE. However, the prebiotic compound Fibregum was found to be having some immunomodulatory effects. Addition of Zn-bacitracin and monensin was highly effective in counteracting the negative effects of the disease challenge.