PSVI-16 - An evaluation using a visual health scoring system with vaginal temperatures of newly received feedlot heifers on immune status

Abstract: Newly received feedlot cattle often experience immune function impairment caused by stressors such as marketing and transportation, resulting in bovine respiratory disease (BRD). Morbidity is often visually detected and medically treated by implementing a 4-point scoring system based on depression, appetite, respiration, and temperature (DART). Using DART scoring, cattle are treated with antimicrobial medications for BRD if they have a rectal temperature (RT) ≥ 40°C and a DART = 2 (scale = 1 to 4), or if they have a DART ≥ 3 regardless of the 40°C RT threshold. However, cattle often exhibit visible clinical symptoms of BRD but do not have a RT ≥ 40°C threshold to warrant medical treatment. Immune status can be measured using a nanotechnology-based immunity test (D2Dx). The objective of this study was to evaluate newly received feedlot heifers on subsequent health status using the DART scoring system and D2Dx values during a 28-d receiving period. Crossbred heifers (n = 198; initial BW = 219 ± 63 kg) were initially processed, weighed, and allocated to one of 10 soil-surfaced pens (12 x 35 m; 20 heifers per pen). A blank controlled intravaginal drug release (CIDR) device attached with indwelling temperature probe (iButton DS1925L) was inserted vaginally into each heifer to record vaginal temperature (VT) every 10 minutes for 28 days. All heifers were evaluated daily (0700 h) for signs of morbidity by three individuals (blinded from each other) implementing DART scoring. Individual DART evaluations were then pooled prior to determination of heifers needing further evaluation for medical treatment. Serum was collected on d 1, 28, and when a heifer was brought to the chute and evaluated for medical treatment (PULL). Initial D2Dx values were not different (P ≥ 0.54) between healthy and morbid heifers upon feedlot arrival. Heifers with DART ≥ 2 that were treated for BRD had decreased (P ≤ 0.05) D2Dx values than healthy heifers with DART = 0. The D2Dx values were not different (P ≥ 0.15) between heifers with DART = 2 and DART = 3. Upon feedlot arrival, D2Dx values were low for all heifers and increased (P ≤ 0.05) by the 1^st and 2^nd PULL. By d 28, D2Dx values were greater (P ≤ 0.01) than both d 0 and all total PULL. Average VT decreased (P ≤ 0.01) from d 0 to 28, implying heifer health status improved by d 28 as D2Dx values increased. In this study, morbidity cannot be determined by D2Dx values upon arrival. Employing the DART scoring method accompanied with the D2Dx immunity test provided an overview of how effective clinical BRD can be diagnosed. Therefore, contributing to the improvement and development of more effective strategies for identifying respiratory diseases in feedlot cattle.