RESUMEN
The investigations were carried out on 22 sows and 44 piglets (one sow and 2 piglets from each litter). The pigs were divided into 4 groups according to the different additions to their diet during weaning which might have an effect on the carrier state and dissemination of beta-haemolytic E. coli. Group I was given a feed concentrate and separated milk, group II - a feed concentrate and sour milk, group III - a feed concentrate and milk with addition of garlic (200 mg/kg of body weight), group IV - a feed concentrate and milk with addition of vitamin C (20 mg/kg of body weight). The beta-haemolytic E. coli carrier state was examined before starting supplemental feeding (3 times between the 21st and 30th day of life) and after weaning (3 times between the 49th and 56th day of life). The carrier state under discussion was found in 27.2% of sows and in 25% of piglets at the beginning of supplemental feeding, and in 40.1% of sows and 36.3% of piglets during weaning, which means an increase of the number of carriers both among the sows and piglets at that time. Twenty-two strains of E. coli isolated from the carriers belonged to serotypes responsible for colibacteriosis of pigs (O149:K91, K88a, c, O8:K87, K88a, c, O139:K82); 23 strains belonging to E. coli groups O6, O8 and O116 were devoid of K and H antigens, 9 strains possessed a double O antigen (O9, O60: :H-, O117, O120: :H-, O102, O25: :H21). An inhibitory effect of the addition of sour milk to the feed on the intensity of the carrier state of beta-haemolytic E. coli was observed in piglets kept on that diet. The pathogenic strains of E. coli were observed more often in the carrier-piglets (60%), and in the sows predominated the strains of beta-haemolytic E. coli devoid of the K antigens.
