In modern agriculture, antibiotics have been routinely used as growth promoters (long-term prophylactic application of antibiotics in sub-therapeutic doses) in animal feeding. Consequently, the widespread application of antibiotic growth promoters has strongly contributed to the development of resistant bacteria (Laxminarayan et al. 2015). This basic situation encounters two completely different global conditions: On the one hand, in industrial nations the demand for healthy food increases. Moreover, in Western societies life expectancy increases and concomitantly the number of elderly, immunocompromised and hospitalised people. These people are more susceptible to chronic infections, many of which are caused by Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. On the other hand, in developing countries, the demand for animal-derived food increases exponentially, reflecting the upgraded lifestyle and upcoming wealth. Nevertheless, in both parts of the world, the containment of the further development of multi-resistant bacteria and with it the protection of consumer’s health represents a major health issue (Givskov 2012). Currently, a complete ban on antibiotics as growth promoters exists only in the European Union and in South Korea. In Australia, New Zealand and Mexico, the feeding of some, but by no means all, antibiotics is prohibited. The USA and Canada plan the withdrawal of antibiotics with relevance for the curation of human bacterial diseases at the beginning of 2017. However, in numerous other countries in the world, a tendency to exacerbate regulations regarding the use of feed antibiotics can also be observed (Laxminarayan et al. 2015).
The post-antibiotic era in animal feeding is associated with two major risks:
- An imminent loss of productivity
- A so far unpredictable increase in intestinal and systemic bacterial infections
The ban on feed antibiotics as growth promoters has expedited the research in alternative substances. Phytogenic substances, such as ground herbs and spices, or preparations, like essential oils, extracts or oleoresins, contain myriad highly active secondary plant metabolites, unfolding a broad range of therapeutic effects, including antibacterial effects. This article briefly reviews the mode of action of antibiotics and evaluates the potential of phytogenic substances as alternatives to antibiotics in animal production.