Young weaned calves are susceptible to viral and bacterial infections. In two studies 279 and 500 weaned calves were injected at random with an adjuvant, with saline or were left untreated in order to evaluate their weight gain or illness and mortality during the first 10 weeks of fattening on a fat-stock farm. However, in contrast to studies reported in the literature, no significantly higher increase in weight gain and no significant improvement of illness and mortality were found with adjuvant treatment.