Trial-1 was conducted with 96 21 d-old piglets. Trial-2 was conducted with 128 pigs (half were 21 days old and half 31 days old). Four dietary treatments were used: control diet; diet with plasma; diet with colistin; and diet with plasma and colistin. When included, plasma was used at 5 per cent during the pre-starter phase and at 2 per cent during the starter phase. In Trial-1 only the improvements in average daily gain (P equal to 0.1) and feed to gain ratio (P less than 0.05) due to plasma and in feed to gain ratio (P less than 0.01) due to colistin reached statistical significance. In Trial-2, plasma improved again feed to gain ratio (P less than 0.05). The statistical significance was mainly due to the improvement experienced by the 22 d-old piglets. It is concluded that this plasma is a good alternative to the use of antimicrobial medication.