PSVI-15 - Assessment of strategies to reduce the incidence and severity of digital dermatitis related lameness in feedlot cattle

Abstract: Lameness is a significant disease in Canadian feedlots, second only to respiratory disease in terms of welfare and economic impact, however, few studies have assessed treatment strategies for infectious causes of lameness. The aim of this study was to compare practical mitigation strategies for digital dermatitis (DD), a common cause of lameness in feedlot cattle. Over two years, lame cattle from 3 large ( >10,000 head) southern Alberta feedlots were pulled weekly and visually confirmed to have DD lesions. Cattle with DD were randomly assigned to one of four treatments: 1) injectable antibiotic (Excenel®; 50 mg/mL or Excede® 200; 200 mg/mL Zoetis Inc., Kirkland, QC, Canada); 2) injectable antibiotic and 5 % copper sulfate pentahydrate footbath one week later; 3) chlortetracycline hydrochloride 2.45% spray (CycloSpray®, Dechra Regulatory BV, Bladel, Netherlands) and footbath one week later; and 4) non-antibiotic topical gel (Intra Hoof-fit gel; Intracare BV, Veghel, Netherlands). Cattle enrolled (n=85) in the study were weighed to access performance (body weight (BW, kg); average daily gain (ADG, kg/d)) and sampled for physiological biomarkers of stress/inflammation (salivary and hair cortisol, haptoglobin, hematocrit, haemoglobin, and white blood cell (WBC), red blood cell (RBC), platelet, lymphocyte, monocyte and granulocyte counts), indicators of lesion healing (4-point healing score and a 4-point gait score)), and rectal temperature taken on the day of diagnosis (D0) and for two consecutive weeks (D7 and D14). Data was analyzed using the GLIMMIX procedure of SAS. Fixed effects were lesion type, gender, time and their interactions, while random effects were animal. A chi-square analysis was conducted to compare the effects of treatments on healing and gait scores. Cattle in groups 1 (antibiotic only) and 4 (hoof gel) had more (p < 0.05) lesions that worsened post-treatment than those in groups 2 (antibiotic and copper sulfate footbath) and 3 (topical antibiotic spray). However, no differences (p>0.10) were observed between treatments for lesions that improved. A time effect (p < 0.01) was observed where saliva and hair cortisol concentrations and WBC, RBC and monocytes counts were greater on D0 compared to D7 and D14 while hematocrit was greater on D0 compared to D7. Overall, indicators of stress/inflammation were greatest on the first day of assessment (D0) but no differences were observed for improved healing between treatments.