For many decades antibiotics have been used as feed additives in various species of farm animals to reduce the frequency of diarrhoea under certain conditions. It can also improve body weight gain or feed conversion ratio. These antibiotics modify the intestinal bacteria and their interaction with the host animal. Public concern has risen over the potential increase of bacterial antibiotic resistance. Some alternatives to antibiotics include probiotics, prebiotics, organic acids and herbs, as well as essential oils. Probiotics are commonly defined as viable microbes that lead to beneficial effects for the host by modifying the intestinal microbial population. It must survive throughout processing, pelleting, storage, and stomach. Some research trials have shown that alternative growth promoters can enhance animal performance. 80% of experiments show that piglets fed probiotics see a reduction in piglet diarrhoea.