**3.1 Health status of animals**

The deficit of colostral feeding on day 4 of life caused clinical symptoms of disease in 8 replacer-fed piglets (i.e. 30.8 % of the total number of 26 piglets). The other piglets from this group were healthy. The sick piglets were apathic and did not show any interest in feeding. The disease was peracute and proceeded with physiological temperature. Even though antibiotics were administered, the piglets died within 8 hrs of the first appearance of symptoms. Rectal smears and blood for hematological examination were taken from the piglets and both pathological and anatomical dissections were carried out. In the piglets, lymphocytic leukocytosis as well as hypochromic anaemia were diagnosed, and *E. coli* K88 was isolated from rectal swabs. The colonies from the final dilutions were verified by slide agglutination with K88ab antiserum (Imuna Šarišské Michaľany, Slovakia). The pathological and anatomical dissection for peracuteness of the course of the disease revealed only petechial bleeding on seroses and mucoses of the gastrointestinal tract. Transudate in the abdominal cavity was of a deep-red colour, and the blood was uncoagulated. In the groups of suckled piglets (natural feeding) and gnotobiotic piglets the health status was good.
