Subclinical Mastitis in Dairy Cows is Associated with Changes in Salivary Serum Amylase-A, Social Behavior and Activity Profiles

ABSTRACT

The relationship between behavior and low-level, subclinical systemic inflammation was investigated in a group of matched-pair (sub-clinical mastitis, SCM, versus clinically healthy control, CTRL) intensively housed dairy cows (n = 34) over short (24h) distinct periods. We report, for the first time, that an increase in an inflammatory marker (salivary serum amylase-A, SAA) occurs during the early stages of a bovine disease. SAA was higher in SCM cows, and positively correlated with somatic cell count, the defining parameter of mastitis. SCM cows were observed to display reduced activity (behavioral transitions and distance moved), and reductions in several measures of social behavior including: social exploration, social reactivity (following the receipt of agonistic behavior), performance of social grooming and head butts, and the receipt of challenges. In addition, SCM cows received more head swipes, and spent a greater proportion of time lying with their head on their flank than CTRL cows. SCM cows also demonstrated a preference for lower-risk ‘within-herd feeding’; a greater proportion of time feeding was spent in direct contact with herd-members, and a lower proportion of time feeding was spent at self-locking feed barriers, than the CTRL cows. We also present evidence for diurnal differences in the daily behavioral routine between the two groups: SCM cows appear to shift their activity (social and otherwise) to quieter times of the day, a tactic that could actively avoid agonism. Many behavioral measures were found to correlate with SAA in a direction consistent with predictions for sickness behavior. We conclude that salivary SAA, social behavior and activity changes offer potential for use in the detection and monitoring of pre-clinical inflammatory disease states in cows.