This study was aimed at the determination of the serum levels of serum amyloid A (SAA), haptoglobin (Hp), ceruloplasmin (Cp) and albumin (Alb), and the salivary levels of Hp and Cp in neonatal calves with diarrhoea. Male and female neonatal Simmental calves, 15 of which were sick and 10 of which were healthy, constituted the study material. Five mL blood samples from the jugular vein and saliva samples absorbed with swabs were collected once from all animals. While serum SAA (P< 0.001), Hp (P< 0.001) and Cp (P< 0.001) levels were found to be significantly higher in the sick calves, compared to the healthy calves, no significant difference was detected for the serum Alb levels (P> 0.05). Furthermore, the salivary Hp (P< 0.05) and Cp (P< 0.001) levels of the sick animals were higher than those of the healthy animals. In result, it was ascertained that serum Hp, SAA and Cp levels and salivary Hp and Cp levels significantly altered in diarrhoeic animals. Thus, it is suggested that in studies involving the measurement of Hp and Cp levels, saliva samples could be collected non-invasively as an alternative to blood samples.