Antimicrobials and competitive exclusion

The compatibility of commonly used antimicrobial feed additives with CE treatment are examined. It appears that additives permitted in the U.K. are without effect on CE, with the possible exception of avoparcin. However, a sharp difference has been found with the effect of antimicrobials on CE treatment cultures in vitro, and the in vivo effect; and it is postulated that these differences may be accounted for by the fact that the substances may not be ‘caecum available’ in the bird. When effects are observed in the bird they appear to be largely due to dose variation. In the case of adult birds already infected with Salmonella, the time between completion of antimicrobial treatment and the administration of Broilact ® will be examined; as well as the selection of propriate antimicrobial treatment in infected birds prior to the administration of replacement microflora.