Necrotic enteritis, currently a billion dollar disease: Is there anything new on the horizon?
In a recent survey, it was estimated that the cost of subclinical necrotic enteritis was as high as US$0.05 per bird (Van der Sluis, 2000). Using these estimates and 1999 estimates on world broiler meat production, the cost of necrotic enteritis to the poultry industry globally is nearly US$2 billion (Anonymous, 2000).
Both clinical and subclinical necrotic enteritis is common in all poultry growing areas of the world (Van der Sluis, 2000). The causative agent of necrotic enteritis is Clostridium perfringens, a nearly ubiquitous anaerobic bacteria that can be readily found in soil, dust, faeces, feed, poultry litter and in intestinal contents (Ficken and Wages, 1997).
Given the ubiquitous nature of C. perfringens, it is not surprising that we cannot attribute the clinical disease, necrotic enteritis, to only one cause. However, it does appear that conditions that result in damage to the intestinal mucosa (coccidiosis, mycotoxicosis) or disturbance to the normal intestinal microflora predispose birds to proliferation of Clostridium (Al-Sheikhly and Al-Saieg, 1980; Elwinger et al., 1992; Ficken and Wages, 1997; Fukata et al., 1991).
The subclinical form of the disease may be the most economically important since it has been shown to impair feed conversion in broilers (Stutz and Lawton, 1984).
Most prevention strategies have taken the form of antibacterial feed additives, often called growth promotants, such as bacitracin, virginiamycin, avoparcin, lincomycin, tylosin and penicillin (Ficken and Wages, 1997; George et al., 1982; Hafshagan and Kaldhusdal, 1992; Maxey and Page, 1977; Stutz and Lawton, 1984, Watkins et al., 1997).
Also, the ionophore anticoccidial agents have been shown to reduce the level of anaerobic bacteria such as C. perfringens (Prescott and Baggot, 1993). Dietary manipulation by lowering the level of fishmeal, wheat, or barley can also help prevent clostridial infections (Ficken and Wages, 1997; Kaldhusdal and Skjerve, 1996).
In 1999, the EU prohibited use of the antibacterial feed additives that have most successfully controlled the incidence of both clinical and subclinical necrotic enteritis. Therefore, new methods to prevent necrotic enteritis must be investigated.
Fukata et al. (1991) found that the pathogenicity of C. perfringens could be reduced by feeding chicks a monoflora of either Lactobacillus acidophilus or Streptococcus faecalis. Others have demonstrated that use of undefined competitive exclusion cultures of chicken intestinal flora, either fresh or freeze-dried, could reduce the incidence of necrotic enteritis, the cecal colonisation of C. perfringens and also prevent subclinical effects on body weight and feed efficiency in broiler chickens (Elwinger et al., 1992; Hofacre et al., 1998).
Control of coccidia, either natural infections or in controlled exposures (live vaccination), becomes more critical in those broiler growing locations that no longer use feed additive antibiotics.
A battery cage study using 960 male broiler chickens (Cobb) was designed to determine the efficacy of various compounds either alone or in combination in controlling necrotic enteritis caused by C. perfringens. Treatments consisted of a control, two competitive exclusion cultures (Avi-Free and All-Lac XCL) and five dietary additives including BMD, Bio-Mos (mannan oligosaccharide), fructooligosaccharide, a herbal supplement and an acid additive.
Broilers treated with All-Lac XCL and Bio-Mos plus All-Lac XCL had the lowest necrotic enteritis-associated mortality.
Article made possible through the contribution of University of Georgia.