Phytochemical Alternatives to Antibiotic Growth Promoters: Ruminant Nitrogen Efficiency at the Nexus of Energy, Food, Water and Health.

Nitrogen is a limiting nutrient in many agricultural systems, and technologies to improve soil nitrogen revolutionized modern agriculture. Fewer tools are available to improve nitrogen (i.e. protein) utilization by animals, but one successful approach is to administer antibiotics in feed.  Feed antibiotics improve feed efficiency and growth in ruminants, and decrease the output of carbon and nitrogen waste. These benefits are achieved by inhibiting particular groups of microorganisms in the digestive tract. Widely used feed antibiotics include non-clinically relevant (e.g. ionophores) as well as more standard (e.g. tetracyclines) classes of antibiotics, which have been implicated in promoting antibiotic resistance.  New regulations restrict the use of some products to preserve antibiotic efficacy.  However, to entirely abandon feed antimicrobials would be to sacrifice the economic and environmental benefits of those technologies.  Phytochemical antimicrobials are an alternative to classical antibiotics that could be used in animal industries.  The red clover isoflavone, biochanin A, is presented as an example of a phytochemical antimicrobial that suppresses some of the same groups of gastrointestinal microorganisms as traditional feed antibiotics. The biochanin A mechanism of action is unlike typical antibiotics, and field trials show the efficacy and suitability as an alternative ruminant growth promoter.