SUMMARY Necrotic enteritis (NE) is an enteric disease of poultry caused by Clostridium perfringens (C. perfringens). The incidence of NE has increased in several countries as a result of restrictions on the use of in-feed antibiotics. This disease may be triggered by a combination of coccidiosis and the presence of undigested nutrients in the hindgut providing nutrients and high pH that favour the proliferation of pathogens. Meat and bone meal (MBM) inclusion rates above 4% and higher dietary calcium (Ca) inclusion rates above 1.0% may potentially favour the overgrowth of enteric pathogens, including C. perfringens. High levels of elastin, collagen and keratin from MBM are refractory to gastric digestion and may act as nutrient substrates for C. perfringens. Such proteins are metabolised by C. perfringens by putrefactive fermentation, producing trimethylamine and ammonia, that affect gut health and increase the pH of digesta. Digesta pH may become elevated by feeding a diet high in Ca, as this nutrient has a high acid-binding capacity. Calcium interacts with phytic acid, forming mineral-phytate complexes that decrease the activity of exogenous dietary phytase. This reduces digestion and increases the influx of nutrients into the hindgut. Similarly, smaller particle sizes (dgw <75 μm) and high solubility of some Ca sources could increase digesta pH and chelation of Ca by phytic acid and decrease nutrient digestibility. Whether the practice of overfeeding Ca in order to ensure this nutrient is not limiting for bone development may be putting the bird at risk of a NE outbreak is not known. This review discusses the potential for dietary MBM to exacerbate NE in broiler chickens. The impact of Ca level and particle size to affect gut pH and phytase efficacy are discussed, with inferences to alter the onset of NE.

中文翻译：

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膳食钙和肉骨粉是坏死性肠炎发作的潜在前兆

总结 坏死性肠炎 (NE) 是一种由产气荚膜梭菌 (C. perfringens) 引起的家禽肠道疾病。由于限制在饲料中使用抗生素，NE 的发病率在一些国家有所增加。这种疾病可能由球虫病和后肠中未消化的营养物质的存在共同引发，这些营养物质提供有利于病原体增殖的营养物质和高 pH 值。高于 4% 的肉骨粉 (MBM) 加入率和高于 1.0% 的较高膳食钙 (Ca) 加入率可能有利于肠道病原体的过度生长，包括产气荚膜梭菌。来自 MBM 的高水平弹性蛋白、胶原蛋白和角蛋白难以被胃消化，并且可能作为产气荚膜梭菌的营养底物。这些蛋白质被产气荚膜梭菌通过腐败发酵代谢，产生三甲胺和氨，影响肠道健康并增加食糜的 pH 值。Digesta pH 值可能会因饲喂高钙饮食而升高，因为这种营养素具有很高的酸结合能力。钙与植酸相互作用，形成矿物-植酸盐复合物，降低外源性膳食植酸酶的活性。这会减少消化并增加营养物质流入后肠。同样，较小的粒径 (dgw <75 μm) 和一些钙源的高溶解度可以增加食糜 pH 值和植酸对钙的螯合，并降低营养物质的消化率。为确保这种营养不限制骨骼发育而过度喂食钙的做法是否会使鸟类面临 NE 爆发的风险尚不清楚。本综述讨论了日粮肉骨粉加剧肉鸡 NE 的可能性。