The Effect of Probiotics on the Gut Micro-ecology of Farm Animals

Abstract

The meaning of the word ‘probiotic’ has changed since it was coined by Lilly and Stillwell in 1965. Originally, it was used to mean a substance produced by one microorganism which stimulated the growth of another, i.e. the opposite of antibiotic. While this was etymologically sound, the meaning was subsequently changed and used to describe feed supplements which had a beneficial effect on the consumer by altering its gut microflora. It was defined as ‘organisms and substances which contribute to intestinal microbial balance’ (Parker, 1974). This definition covers preparations specifically designed to have beneficial effects on the growth and health of the animal; and also yoghurt and other fermented milks, which, have, over many years, acquired a health-benefit image, despite being developed initially for other reasons. It also covers a wider variety of substances like antibiotics which it was not intended to include. Therefore, Fuller (1989) modified the definition to read ‘A live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance’. This revised definition stresses the viable nature of the probiotic and removes the confusion created by the word ‘substances’.