It was testet wto types of intestinal microflora of adult chikens (one from field and other from the industiual explotation) for testing their inhibitory effect in the colonization of the Salmonella pullorum in groups of pullets of differente ages, without finding significant differences between them, resulting protected the 70% of the population and abreviating the period of excretion when were placed in contact with the seeders birds it was found that the protection was given in pullets of one day; old because the resistence increased with the age. The protective mechanism appears to be a consecuence of competitive exclusion between the normal intestinal microflora o f the gastrointestinal trat and the Salmonella sp. by sities of ttachament on the intestinal mucosa.