Abstract
The development of new/different management and feeding strategies to stimulate gut development and health
in newly-weaned pigs, in order to improve growth performance while minimizing the use of antimicrobial
compounds such as antibiotic growth promotants (AGP) and heavy mineral compounds, is essential for the
long-term sustainability of the pig industry. Factors including the sub-optimal intake of nutrients and energy,
inappropriate microbiota biomass and (or) balance, immature and compromised immune function, and
psychosomatic factors caused by weaning can compromise both the efficiency of digestion and absorption and
intestinal barrier function through mucosal damage and alteration of tight junction integrity. As a consequence,
pigs at weaning are highly susceptible to pathogenic enteric conditions such as post-weaning diarrhea that may be
caused by serotypes of enterotoxigenic Escherichia coli. Many dietary components, e.g., protein, fiber, feed additives
and minerals, are known to influence microbial growth in the gastrointestinal tract that in turn can impact upon
pig growth and health, although the relationships between these are sometimes not necessarily apparent or
obvious. In a world climate of increased scrutiny over the use of antibiotics per se in pig production, certain feed
additives are seen as alternatives/replacements to antibiotics, and have evolved in some cases to have important
roles in everyday commercial pig nutrition. Nevertheless and in general, there remains inconsistency and variability
in the efficacy of some feed additives and in cases of severe disease outbreaks, for example, therapeutic antibiotics
and/or heavy minerals such as zinc oxide (ZnO) are generally relied upon. If feed ingredients and (or) feed additives
are to be used with greater regularity and reliability, then it is necessary to better understand the mechanisms
whereby antibiotics and minerals such as ZnO influence animal physiology, in conjunction with the use of
appropriate challenge models and in vitro and in vivo techniques.