151 Effectiveness of portable near infrared spectroscopy for chute-side determination of hot-iron brand age in growing beef cattle

Although livestock law enforcement professionals consider hot-iron branding as an effective deterrent, theft of branded animals may still occur if the original brand is altered, thus creating different ages of burn scar tissue on an animal. Hot-iron brands were applied to growing beef steers to determine if portable near infrared spectroscopy could predict the age of hot-iron brands applied on different dates. Brands were applied to 21 Angus cross steers at approximately 3 and 7 months-of-age. Brands were randomly assigned to each steer in one of three locations (n = 7 each); hip, rib, and shoulder. Brand location was rotated forward for the second application; e.g. an animal branded on the hip at 3 months was branded on the rib at 7 months. Spectra (400-2500 nm) were collected with an ASD Field Spec Pro® from 3 replicates of branded and non-branded skin on each animal, approximately 2 hours after each brand application. At 7 months, spectra were collected from both the recent (NEW) and former (OLD) brands. Identification of brand age groups and prediction of brand age (0.5 and 145-d) were accomplished via principal component cluster analysis and multiple partial least squares regression procedures, respectively. Differences in proportions of group identification were determined via chi square procedures. Predictive calibration performance was evaluated based on multiple coefficient of determination (RSQ), and the root mean square error of a full leave-one-out cross-validation (SECV). Difference in brand age between groups was determined via analysis of variance. Significance was determined at P < 0.05. Unsupervised cluster analysis on spectra from branded skin produced groups (P < 0.01) consisting of: a) 80% NEW and 20% OLD branded skin, and, b) 2 % NEW and 98% OLD branded skin. The brand age prediction calibration resulted in an RSQ = 0.92 and SECV = 20.9 days. Mean predicted brand age (P < 0.01) was 5.4 ± 2.6 and 140.1 ± 2.2 days for the 0.5-d and 145-d groups respectively. The standard deviation was 19.6 days for the 0.5-d group and 16.7 days for the 145-d group. Similar to other studies, portable near infrared spectroscopy was able to accurately discriminate between brands applied at two different dates on the same animal. Identification of brand age group was approximately 90% successful in these 7-month-old steers and thus, could be used to determine if a given brand has been altered. Prediction of brand age was also successful, but the standard deviation indicates that this technique may not currently be sufficiently accurate for legal applications if establishment of an actual date of brand application is called for. Further evaluation of this technique in diverse animal classes and field environments is thus called for.