The yolk immunoglobulin (IgY) preparate was added to the fodder of piglets to establish its prophylactic role in the periods of highest incidence of diarrhea. IgY was added in the proportion of 0,5g (Dl), lg (02) or 2g (03) /kg of the fodder, (control group without IgY) and given to suckling piglets (5-21 days old, in summary 873 from 81 sows at four groups, experiment 1.), or to piglets during first 30 days after weaning (15 piglets in each of the groups, experiment 2.). Experiment 1.: diarrhea occurred in 6.72% of suckling control piglets whereas no diarrhea was found in Dl group, in 0.92% of 02, and in 3.21% of 03 group. The incidence of other diseases was also higher in control than in experimental groups. The percent of reared piglets was significantly higher in experimental ( 89.17-91.98%, than in the control (82.21 %) groups.