Probiotics are genetically identifiable, live microorganisms that when administered in adequate amounts, confer appropriately sized health benefit (e.g. correcting dysbiosis, immunomodulatory effect) on a target host. In cattle, probiotics have shown promising results and long-term benefits in productivity when used on animals under stress. The health and production benefits of probiotics were attributed to improvement in fermentation in rumen and intestine, the stabilisation of rumen pH, and improvements in the intestinal barriers. In the bovine udder, a dysbiosis of the commensal intramammary microbiota and the presence of mastitis causing-bacteria has been linked to increased intramammary infections. Probiotic bacteria capable of biofilm formation inside the udder either serve as a barrier against pathogens or disrupt and replace biofilms formed by pathogens. Over the past two decades, several types of probiotics have been used as feed additives; however, the effect of probiotic use on disease prevention and cattle health and performance indicators, and characterisation of the immunomodulatory association between probiotic microbiota and host target system microbiota are yet to be quantified or documented.

益生菌是遗传上可鉴定的活微生物，当以足够的量施用时，可以对目标宿主产生适当大小的健康益处（例如，纠正营养不良，免疫调节作用）。在牛群中，益生菌在压力下的动物身上使用时，已显示出令人鼓舞的结果和长期的生产力优势。益生菌的健康和生产效益归因于瘤胃和肠发酵的改善，瘤胃pH值的稳定以及肠屏障的改善。在牛乳房中，共乳内微生物群的营养不良和乳腺炎引起细菌的存在与乳内感染的增加有关。能够在乳房内部形成生物膜的益生菌可以作为抵抗病原体的屏障，也可以破坏和替代由病原体形成的生物膜。在过去的二十年中，几种益生菌已被用作饲料添加剂。然而，益生菌的使用对疾病预防，牛健康和性能指标的影响，以及益生菌微生物群和宿主靶标系统微生物群之间免疫调节关联的表征尚待定量或记录。