Microbiological assessment of four probiotic feed supplements used by the dairy industry in New Zealand

Since Metchnikoff's publication “The Prolongation of Life” (Metchnikoff 1908) proposed the use of live bacteria to improve health, a precise definition of probiotics has yet to be formulated, however a widely held definition is “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host” (FAO/WHO 2002). However, an on-going challenge with using probiotics is maintaining their viability while they are stored and sold. This challenge is compounded when probiotics are used in agriculture as feed supplements, since it may not be economical to use freeze drying or refrigeration to maintain the viability of microbes in a product. We analysed four agricultural probiotic feed supplements used by the New Zealand dairy industry, to estimate the number of live probiotic microbes in each product using a combination of culture techniques, particle size analysis and live/dead staining.