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Effect of metaphylaxis on production responses and antimicrobial usage in high-risk steers
A trial was conducted to determine the effects of on-arrival metaphylaxis in beef cattle for controlling bovine respiratory disease (BRD) and determining subsequent effects on health and performance. Male calves in a randomized complete block design (n=198, arrival weight= 231 kg ± 2.43) received either 3.3 ml/100 kg (6.6 mg/kg) ceftiofur crystalline free acid (EXC), 4.4 ml/100 kg (13.2 mg/kg) tilmicosin phosphate (MIC), or were not treated (CON). These products are commonly used in production settings. Cattle receiving metaphylaxis had 25.2% lower morbidity rates than CON (P = 0.01; 51.5 versus 76.7%). Significant differences were not observed in morbidity rates (P = 0.14) between cattle on the MIC (46.4 ± 4.32%) or EXC treatments (56.5 ± 4.32%). Of cattle requiring BRD therapy, the CON group displayed symptoms approximately 5 days earlier than cattle in the metaphylaxis group (P = 0.01). Cattle displaying BRD symptoms in the MIC group required treatment 3 days earlier than those in the EXC group (P = 0.02, 8 versus 11 days, respectively). Metaphylaxis improved average daily gain (1.63 versus 1.28 kg/d; P = 0.06) and G:F (0.29 versus 0.22, P = 0.01) during the first 14 d compared to CON, but differences between EXC and MIC were not significant (P > 0.40) during the first 14 d. Despite differences at 14 d, no differences were observed in ADG (P = 0.20) or G:F (P = 0.18) between CON and treatment groups across the 42 d trial. Total antimicrobial usage was 6.03 vs. 6.16 of g active ingredient per animal for CON vs. metaphylaxis (P = 0.88), and 5.99 vs 6.33 for MIC vs EXC (P = 0.74). These results suggest that both tilmicosin phosphate and ceftiofur crystalline free acid effectively reduce overall morbidity and delay onset of clinical illness in newly received beef cattle. Furthermore, this reduction in overall morbidity was achieved with minimal increase in total antimicrobial usage. While overall performance outcomes were not different, animal health was improved with metaphylaxis.
Keywords: bovine respiratory disease, metaphylaxis