These are specific strains of live bacteria and yeasts which when fed to an animal are designed to populate the gut and provide a beneficial effect on the host. These microorganisms are able to colonise the digestive tract and reproduce, assisting digestion and overall health by competing with non-beneficial or pathogenic organisms. Essentially the concept is that if you flood the gut with ‘’good bugs’’ they will use up most of the nutrient supply and starve out the populations of ‘’bad bugs’’.
Strains of bacteria include Lactobacillus acidophilus, Lactobacillus. casei, Enterococcus faecium, and Bifidobacterium thermophilum. However, like prebiotics, most of the research has been done in species other than the horse and questions remain about whether the commercially available probiotic microbes remain viable whilst passing through the highly acidic horse stomach and reach the hind gut in sufficient numbers to establish viable populations long term. Minimum effective dose rates and appropriate duration of feeding for different probiotic species have in some cases, but not always been established scientifically. Many commercial products sold for horse use lack scientific credibility. That said, one of the most popular Australian made probiotics does have some solid research background in relation to reducing foal diarrhoea.