Letter to the Editor: A Response to the Comments of Borderas et al. (2007)

The authors propose that increased morbidity and mortality in our study was caused by administration of refused calf milk replacer (CMR) by esophageal feeder. They wrote “we suggest that the increased incidence of illness observed in the calves fed the higher levels of milk replacer was due to sick calves being force-fed.” They further suggested that feed refusals were a manifestation of anorexia caused by expression of proinflammatory cytokines. To determine the role of proinflammatory cytokines in any observed anorexia, we measured concentrations of tumor necrosis factor-α (TNF-α) in blood samples on d 7, 14, 28, 42, and 56. Regarding the interaction of cytokines, anorexia, and illness, we wrote (p. 215) “Although we recorded temporal changes in TNF-α concentrations in blood, these changes were unrelated to dietary treatment. . . There were no differences in proportion of calves refusing CMR or in the number of refusals recorded. Additionally, there were no effects of feeding regimen on concentrations of plasma TNF-α, suggesting that feeding method per se had no effect on anorexia or the calf’s ability to use ingested nutrients.”