Is adenosine deaminase (ADA) activity in saliva and serum a more accurate disease detection tool than traditional redox balance parameters in early-lactating dairy cows?

Enzyme adenosine deaminase (ADA) is a marker of inflammation in domestic animals, but it is unclear whether it is a reliable marker of oxidative stress, especially in the transition period in dairy cows. This study aims to assess if ADA and redox status measurements in saliva provide the same utility to detect disease condition as that obtained from serum. Sixty-eight multiparous Holstein cows, between 2 and 3 weeks postpartum were selected. Five study groups were established: control (healthy), and cows with ketosis, mastitis, laminitis, and metritis. The parameters measured were ADA activity, total oxidants (TOS), antioxidants (TAC), and OSi ratio. Regarding redox status, no significant differences arise in both saliva and serum being the correlations negative and not significant. In saliva, ADA activity in healthy cows differs from those with pathological processes, having the lowest activities. In serum, ADA activity is similar in the healthy and ketosis cows, showing the lowest activities meanwhile animals with mastitis, laminitis, or metritis have significantly higher activities. In conclusion, the measurement of ADA activities and redox status in saliva does not give consistent results, being preferable to measure them in serum during the transition period.