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Effects of Feeding a Novel Amino Acid-Complexed Trace Mineral Supplement on Productivity and Digital Dermatitis Mitigation in Growing-Finishing Feedlot Heifers
Our objectives were to evaluate the efficacy of feeding a novel nutritional supplement providing trace minerals (CTM; zinc (Zn), manganese (Mn), and copper (Cu) as amino acid complexes and cobalt glucoheptonate compared to a supplement that provided a trace mineral profile from predominantly inorganic sources (Control; CON) on incidence and severity of digital dermatitis (DD) and related production parameters for growing-finishing feedlot heifers. Both treatments provided ethylenediamine dihydroiodide (EDDI) as a source of iodine. Analyzed values for diet samples (n=33) for CON and CTM diets, respectively, were (mg∙kg-1DM): Cu: 19 and 20; Mn: 62 and 102; Zn: 97 and 124. The study was conducted on a commercial feedlot with a history of DD. Following a 30 d starting period, 1,120 growing-finishing heifers (Initial BW = 277 kg) were randomly allotted to 8 pens (140 heifers / pen; 4 CON and 4 CTM pens). Heifers were fed the same basal diet, with ractopamine (300 mg∙hd-1∙d-1 fed the last 30 d prior to slaughter. On d 189, heifers were sorted into terminal slaughter groups with total d on study being 323 (Heavier group) and 387 (Lighter group). Heifers were visually evaluated and scored for DD lesion incidence and severity using the M-stage system (M0, M2 and M4 lesions) four times throughout the study (d 70; d 148; d 189; d 248). Baseline prevalence of DD lesions was negligible and similar at initial evaluation (d 70) and increased throughout the trial with greatest prevalence observed post d 188. Feeding CTM reduced overall rate of increase for prevalence of DD lesions (active M2+chronic M4 lesions; P ≤ 0.001) compared to CON. Total weight gain for the entire trial was increased by 8 kg (P ≤ 0.09) and carcass weight increased by 5.9 kg (P ≤ 0.10) for CTM compared to CON heifers. Logistic regression analyses indicated an increase in individual animal carcass weight (HCW) of 11.8 kg (95% C.I. 5.40 – 18.7 kg) determined as a departure from overall centered mean value (HCWc) for CTM heifers compared to CON heifers. Results confirmed previous research indicating the increase in prevalence of active M2 +chronic M4 DD lesions observed with increasing days on feed was significantly mitigated in the CTM pens compared to CON pens. Providing CTM supplementation was associated with improvements in growth performance and carcass yield compared to CON pens which would provide economic benefits to feedlot management.
KEY WORDS: digital dermatitis; feedlot, trace mineral supplementation