It was initially thought that AGPs, being antimicrobial in nature, would be necessarily
counterproductive in animal species where a very significant part of digestion is done by microbes.
This reasoning mainly applies to ruminants, but can be extended to hindgut-fermentation herbivores,
such as the rabbit. Practical experience, supported by scientific evidence, showed that this was not
necessarily the case. Some AGPs improve the performances of ruminants and rabbits. Zinc bacitracin
was the most used AGP in rabbit feed.