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    • CCK-8 synthesis Animal fat appears to increase C perfringens

    2022-11-24

    Animal fat appears to increase C. perfringens counts compared with vegetable oil, so there may indeed be some advantage to vegetable diets at least in terms of fat sources (Knarreborg et al., 2002). Small grains such as wheat, rye, oats, and barley, with high levels of non-starch polysaccharides are predisposing factors compared to corn (Timbermont et al., 2011, M’Sadeq et al., 2015). In one study, distillers dried grains with solubles (DDGS) increased the effects of a coccidiosis and C. perfringens challenge model in a wheat/barley/sorghum diet (Barekatain et al., 2013). Finely ground diets (especially when small grains are used) appear to predispose to the problem (Branton et al., 1987). Anything that causes irritation of the gut, secretion of mucus, or decreased protein digestion and CCK-8 synthesis may predispose to necrotic enteritis, such as feed outages, sudden changes in diet composition, mycotoxins, under- or over-cooked soybean meal, tannins, and so forth (McDevitt et al., 2006, Timbermont et al., 2011, M’Sadeq et al., 2015). Least-cost formulation, the use of lower priced, lower quality ingredients, sourcing of less commonly used alternative ingredients to which the birds are not accustomed, and frequent changing of raw materials to realize buying opportunities may all cause problems. Successful RWA/NAE programs are expensive, and the cost of a quality diet is part of that increased expense. Wet litter is strongly associated with necrotic enteritis (Hermans and Morgan, 2007) so management of the diet and ventilation to maintain dry litter is important. Clostridia dislike acidic environments and high salt concentrations, so acidification or salting of the litter may help. Sodium bisulfite, alum, salt, or Glauber’s salt (sodium sulfate) at roughly 0.25 Kg/m2, and liquid muriatic acid have been recommended as litter treatments. Some clinicians believe that acidification of the water helps control NE; various combinations of short-chain volatile fatty acids (typically acetic and propionic), mineral acids (sodium bisulfite), methionine, and iodine are used. Care must be taken that concentrations do not restrict water intake or result in wet litter. High stocking density has been cited as a predisposing factor for necrotic enteritis (McDevitt et al., 2006). Whether stocking densities can be reduced enough to significantly impact the incidence of necrotic enteritis while still being commercially and economically feasible is unknown, and recommendations for minor reductions in stocking density as a tool to control necrotic enteritis are difficult to support. Breed may influence susceptibility to necrotic enteritis (Hermans and Morgan, 2007), and Smith (2016) documented significant differences in apparent susceptibility between crosses of two different male lines on the same female line during a large field outbreak. The odds of NE were 3.97 times as great (95% confidence interval 3.00-5.24, p < 0.0001) for breed cross A x B compared to breed cross A x C. The antibiotic alternatives are also promoted as aids to control of necrotic enteritis. The one NE vaccine available in the United States is an alpha toxoid for administration to breeder pullets to provide maternal antibody to progeny. Alpha toxin has been shown not to be critical in the pathogenesis (Timbermont et al., 2011), and a limitation of any maternal vaccination strategy is that the peak age of occurrence of necrotic enteritis (usually at 16-21 days of age) coincides with the decline in maternal antibody. Studies to date suggest that a single vaccination at day of hatch will not be sufficient for toxoids and surface protein vaccines, and multiple parenteral injections are not practical in broilers (Mot et al., 2014).
    Gut barrier function and associated issues
    General Disease Prevention Measures In a study in the United Kingdom, a number of variables related to hygiene and biosecurity were associated with lower NE occurrence, including use of dedicated clothing and footwear, hand washing, down time greater than 14 days, and cleaning and disinfection (Hermans and Morgan, 2007). Since treatment must be minimized, general disease prevention becomes more important than ever. Biosecurity practices should be designed to minimize not just catastrophic but also local endemic diseases. Ventilation, water, litter, light, and feed presentation should be managed to decrease stressors, respiratory challenges, and challenges to the skin barrier. Vaccination programs for both the breeders and the broilers, particularly for immunosuppressive diseases (Marek’s Disease, Infectious Bursal Disease, and Chicken Infectious Anemia) and respiratory diseases should be robust, and proper administration carefully monitored. Adequate down time between flocks is even more critical for RWA/NAE programs than conventional programs.