The objectives of this study were to evaluate changes in weight shifting between legs while standing on a weighing platform in response to
endotoxin-induced clinical
mastitis, and to evaluate the effect of the nonsteroidal antiinflammatory
drug flunixin meglumine on weight distribution between legs while standing in dairy cattle with
endotoxin-induced clinical
mastitis. Clinical
mastitis was induced in 10 primiparous and 9 multiparous lactating dairy cows (days in milk=55 ± 12; mean ± standard deviation) by intramammary infusion of 100 µg of Escherichia coli
lipopolysaccharide (LPS) into the right rear quarter. Four hours later, 10 animals were randomly assigned to receive
flunixin meglumine intravenously (2.2mg/kg of
body weight; treated group) and 9 received an equivalent volume of sterile isotonic
saline solution (control group). Body temperature was monitored rectally 3d before LPS infusion, immediately before LPS infusion, and 4, 7, 10, 13, 16, and 28 h after LPS infusion. The weight applied to each leg was recorded while cows were standing on a weighing platform on the day before the challenge and 7, 10, 13, 16, and 28 h after LPS infusion. Two measures of weight shifting between the rear legs were calculated for each recording session: the standard deviation of the weight applied to the legs over time and the frequency of steps. The LPS infusion resulted in a consistent case of clinical
mastitis approximately 4h after the LPS infusion, as assessed by the presence of visible swelling and elevated rectal temperature in all cows. However, control animals had a higher temperature 7h after LPS infusion compared with treated animals (40.8 vs. 39.0°C; standard error of the difference=0.2). Overall, weight shifting between the rear legs was decreased 7h after the LPS infusion compared with baseline, and this decrease was not affected by treatment with
flunixin meglumine. It is likely that weight shifting increases friction between the swollen udder and the legs, increasing the
pain experienced by the cow. Thus, cows with
endotoxin-induced
mastitis avoided shifting weight, particularly at the times when the most severe signs of
inflammation occurred. Further research is needed to assess the efficacy of
flunixin meglumine in mitigating udder
pain and the accuracy of behavioral measures such as weight shifting in assessing
analgesia in cows with
mastitis.