A multiparametric approach to assessing residual pain experienced by dairy cows undergoing digestive tract surgery under multimodal analgesia

Abstract

This study assessed residual pain responses of dairy cows undergoing fistulation surgery under multimodal analgesia using a multiparametric method combining behavioural and physiological indicators. A longitudinal study was conducted on five dairy cows, each acting as her own control. The surgery consisted of implanting a ruminal and a duodenal cannula in each cow. The multimodal drug protocol consisted of a combination of N-Methyl-D aspartic Acid antagonists, α2-agonists, and local anaesthetic during surgery, and non-steroidal anti-inflammatory drugs (NSAIDs) and opioid treatment postsurgery. Cow responses to surgery were monitored by direct behavioural observation, physiological assay indicators, and milk production from day (D) −6 days before surgery (D-6) to D13 postsurgery. From the data recorded, the variables that contributed most to the discrimination of days pre- and postsurgery were identified using factorial discriminant analysis. Components 1 and 2 of the factorial discriminant analysis explained 68.2% and 17.9%, respectively, of the total variance. Component 1 was mainly explained by haptoglobin (contribution to axis: 0.885), oxidative stress (ratio of oxidized gluthatione to reduced glutathione (GSH/GSSG), −0.746; vitamin E, −0.683; vitamin A, −0.597; malondialdehyde (MDA), 0.416), and behavioural indicators (general attitude, 0.594). On this axis, the higher the score, the higher were the apathy and haptoglobin and MDA concentrations, and the lower were the GSH/GSSG ratio and concentrations of vitamins A and E. This axis opposed cows on D-6 to cows on D3 and D5; cows on D1 and D13 were intermediate. Component 2 was mainly explained by the Hypothalamic-pituitary-adrenal axis (non-esterified fatty acid (NEFA), 0.686; cortisol, 0.669), milk yield (−0.725), oxidative stress (MDA, −0.584; nitric oxide (NO), 0.454), and behavioural indicators of pain (ear position, 0.467; leg postures, 0.431). On this axis, the higher the score, the higher the NEFA, cortisol, and nitric oxide concentrations; the more the ear and leg pain postures; and the lower the milk production and MDA concentrations. This axis opposed cows on D13 to cows on D1. These results suggest that cows may experience some pain only on D1, whereas on subsequent days, the inflammatory response and oxidative stress did not seem to be associated with pain. Our results should be considered for different surgeries to improve analgesia immediately after surgery, and to provide antioxidants along with NSAIDs to promote recovery.