Stanton PhD Thesis final_docx - Atrium - University of Guelph

primarily are administered to calves prior to disease outbreaks, and the long follow-up time for
calf stock, which included an extended period of low disease risk. However, these estimates
likely underestimate the cost of BRD due to the difficulty in associating a disease event with
outcomes many months later. The European estimate of 18-57 euros ($ 25-81 U.S.) per case is
likely more accurate since the effect of BRD on growth, long-term survival and productivity
were considered (van der Fels-Klerx et al., 2001). However, the effects of BRD on growth,
survival and production were based on a small number of studies examining these factors that
were conducted 10-20 years ago. Results from these three studies found that BRD increased the
risk of mortality prior to calving (Waltner-Toews et al., 1986), decreased growth (Virtala et al.,
1996), increased age at calving (Waltner-Toews et al., 1986; Correa et al., 1988) and increased
the risk of dystocia at first calving(Warnick et al., 1994). Warnick et al, (1995; 1997) found no
association of calfhood BRD with first lactation milk production or survival after first calving.
The welfare costs of BRD can be substantial based on both the clinical state and the long-
term implications of this disease. The clinical signs can include inappetance, depression,
coughing and shortness of breath (dyspnea), which compromise animal welfare (Mellor and
Stafford, 2004; Kahn, 2005). The long-term effects of BRD on body weight gain and survival are
of concern since these persistent consequences have the potential to decrease calf welfare.
Specifically, decreased growth may be due to a lower dominance status leading to decreased
ability to access resources or an ongoing disease challenge, which would be associated with
ongoing clinical signs. In both of these scenarios animal welfare would be affected and new
management techniques and treatments for affected animals are necessary to improve
convalescence in these animals and to reduce the long-term impacts of this disease.
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