The use of antibiotics to maintain animal well‐being, promote growth and improve efficiency has been practised for more than 50 years. However, as early as the 1950s, researchers identified concern on the development of resistant bacteria for the antibiotics streptomycin and tetracycline used in turkeys and broilers respectively. These findings laid the groundwork for agricultural officials to impose stricter regulatory parameters on the use of antibiotics in poultry feeds. Probiotics are live micro‐organisms included in the diet of animals as feed additives or supplements. Commonly known as a direct‐fed microbial, probiotics provide beneficial properties to the host, primarily through action in the gastrointestinal tract (GIT) of the animal. Supplementation of probiotics in the diet can improve animal health and performance, through contributions to gut health and nutrient use. For instance, supplementation of probiotics has been demonstrated to benefit farm animals in immune modulation, structural modulation and increased cytokine production, which positively affect the intestinal mucosal lining against pathogens. Bacillus subtilis has been a popular bacterium used within the industry and was shown to improve intestinal villus height. Increasing the villus height and structure of the crypts in the GIT allows for the improvement of nutrient digestion and absorption. Tight junctions maintain important defences against pathogenic bacteria and cellular homeostasis. Heat stress can be a major environmental challenge in the poultry industry. Heat stress causes the bird to fluctuate its internal core temperature beyond their comfort zone. To overcome such challenges, poultry will attempt to balance its heat production and dissipation through behavioural and physiological adaptation mechanisms.

中文翻译：

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家禽饲料中的益生菌：全面审查

使用抗生素来维持动物健康、促进生长和提高效率已经实践了 50 多年。然而，早在 1950 年代，研究人员就发现了对分别用于火鸡和肉鸡的抗生素链霉素和四环素产生抗药性细菌的担忧。这些发现为农业官员对家禽饲料中抗生素的使用施加更严格的监管参数奠定了基础。益生菌是作为饲料添加剂或补充剂包含在动物饮食中的活微生物。益生菌通常被称为直接喂养的微生物，主要通过在动物胃肠道 (GIT) 中的作用为宿主提供有益特性。在日粮中补充益生菌可以改善动物的健康和生产性能，通过对肠道健康和营养利用的贡献。例如，补充益生菌已被证明在免疫调节、结构调节和增加细胞因子产生方面有益于农场动物，这对抵抗病原体的肠粘膜内层产生积极影响。枯草芽孢杆菌一直是业内常用的细菌，并被证明可以改善肠绒毛高度。增加 GIT 中隐窝的绒毛高度和结构可以改善营养消化和吸收。紧密连接维持对病原菌和细胞稳态的重要防御。热应激可能是家禽业的主要环境挑战。热应激导致鸡的内部核心温度波动超出其舒适区。为了克服这些挑战，家禽将尝试通过行为和生理适应机制来平衡其产热和散热。