Nonsteroidal anti-inflammatory drug therapy for neonatal calf diarrhea complex: Effects on calf performance

Todd, C. G.; Millman, S. T.; McKnight, D. R.; Duffield, T. F.; Leslie, K. E.

Overall, MEL-treated calves experienced greater BW gain after diarrhea compared with PLA-treated calves. This increased growth can likely be attributed to differences in metabolism and nutrient intake. During disease states, proinflammatory cytokines target the CNS and other organ systems, including skeletal muscle, the liver, and adipose tissue, to cause a shift in the balance between anabolic to catabolic processes (Johnson, 1997) . Proinflammatory cytokines in the CNS inhibit the production of GHRH and thyrotropin-releasing hormone, thereby leading to reductions in plasma concentrations of GH and IGF-I (Sartin et al., 1998) . In skeletal muscle, proinflammatory cytokines cause increased muscle protein catabolism and reduced AA uptake (Johnson, 1997) . Many of the AA from muscle proteolysis are diverted to the liver to support acute phase protein production. Positive acute phase proteins are markers of inflammation and are synthesized in large numbers in response to immune activation (Horadagoda et al., 1999) . The release of proinflammatory cytokines also affects fat metabolism in adipose tissue, causing increased lipolysis and reduced lipoprotein lipase activity (Johnson, 1997) . These metabolic responses, together with changes in milk consumption, may have contributed to the slight depression in BW gain by MEL-and PLA-treated calves during wk 2 after diarrhea. However, this reduction in growth was more marked for PLAtreated calves. Therefore, MEL therapy may have acted by mitigating some of the sickness-induced changes in metabolism. During the later stages of the study period, MEL-treated calves tended to experience larger BW gain than PLA-treated animals. These differences in growth were probably an effect of improved consumption of milk and calf starter ration by MEL-treated calves. In feedlot cattle with bovine respiratory disease, long-term improvements in BW gain after treatment with MEL and antimicrobial therapy, compared with a positive control, have also been reported (Friton et al., 2005) .