Submitted to: Progressive Cattlemen
Publication Type: Popular Publication
Publication Acceptance Date: 2/21/2016
Publication Date: 3/1/2016
Citation: Flythe, M.D., Aiken, G.E. 2016. Red clover: An alternative to antibiotic growth promoters?. Progressive Cattlemen. Pgs. 36-38.
Interpretive Summary: People have always used food to overcome illness and improve health. Human nutritionists have recently started calling foods with medicinal value functional foods. We borrowed that idea to look for a functional feed, a plant, or plant-based product, which could be used to achieve the same benefit as antibiotic growth promoters. Because red clover is so rich in biologically active compounds, we chose to look there first. To evaluate clover compounds as antimicrobials, we first need to understand how antibiotic growth promoters work. Most antimicrobial growth promoters that we use are antibiotics, that is, they are made by microorganisms to kill other microorganisms. The rumen is densely populated with many types of bacteria and other microorganisms. Some bacteria, like those that break down fiber, are very important. Cattle cannot get energy from grass or hay without these bacteria. Others carry out wasteful processes, such as protein degradation. Think of these wasteful bacteria as weeds; they decrease the productivity of a rumen in the way that weeds can decrease the productivity of a pasture. Antimicrobial growth promoters can increase the productivity of a rumen by the same ecological principle that herbicides can increase the productivity of a pasture, by selectively controlling the growth of certain species. Antimicrobial growth promoters, like herbicides, are tools that allow you to direct nutritional resources the way that you want them to go. Plant protein passes into the rumen; it is broken down into amino acids by one group of microorganisms; then another group converts the amino acids into ammonia. Beneficial bacteria recapture some of the ammonia, but much of it is transported into the blood and is lost in the urine. When ammonia production decreases, more protein-nitrogen makes it into animal tissue. Protein and amino acids that survive the rumen are called bypass protein, and can be absorbed by the animal in the lower digestive tract. The group of rumen bacteria that convert most of the feed amino acids into ammonia is called the Hyper Ammonia-producing Bacteria (HAB). Antimicrobial growth promoters kill HAB, which increases bypass protein, feed efficiency and weight gain. We began by extracting a mixture of compounds from red clover (cultivar Kenland). The extract was tested against rumen HAB in our USDA-ARS laboratory at the University of Kentucky. It was determined that the extract could prevent the growth and ammonia production by the HAB. This result indicated that red clover contained at least one compound that had the desired antimicrobial property. The natural products in the extract were chemically separated and screened for activity using the pure HAB culture. The compound that prevented growth of the HAB was identified as an isoflavone called biochanin A. Once it was determined that the red clover isoflavone, biochanin A, could reduce ammonia production from rumen bacteria by killing the same bacteria as antibiotic growth promoters, then the next step was to test its ability to promote growth in cattle. We carried out two grazing trials in the spring and fall of 2015. In each trial, 48 Angus cross steers were put on pasture (novel endophyte fescue with no legume) in one of three groups: pasture only, pasture plus dry distillers’ grains or pasture plus dry distillers’ grains with added biochanin A. The biochanin A was given at 7 g per head a day, which is equivalent to the amount of biochanin A in a diet of approximately 1/3 red clover. The average daily gains were calculated at the end of the 63- and 61-day trials. The trials have not been reported in a scientific journal, but the results are promising in showing improved average daily weight gain with the addition of biochanin A. We believe that the isoflavones, including biochanin A, and other bio-active compounds may explain many o
Technical Abstract: A series of experiments were conducted at the Forage-Animal Production Research Unit to discover a growth-promoting natural product from red clover (Trifolium pratense). Previously published work included a bioassay for antimicrobial activity of phytochemicals. The bioassay was used to discover the antimicrobial activity of the isoflavone, biochanin A, against the rumen Hyper Ammonia-producing Bacteria (HAB), Clostridium sticklandii. It was subsequently determined that biochanin A inhibited the growth of other HAB species of both bovine and caprine origin. Feeding trials were conducted in which pastured steers were supplemented with purified biochanin A. Preliminary evaluation indicates that biochanin A improved average daily gain.