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Use of clinic refractometer at farm as a tool to estimate the IgG content in goat colostrum

Castro, Noemí, Gómez-González, Lenny Andrea, Earley, Bernadette, Argüello, Anastasio
Journal of applied animal research 2018 v.46 no.1 pp. 1505-1508
colostrum, dairy goats, enzyme-linked immunosorbent assay, farms, immunoglobulin G, milk, refractive index, regression analysis
Refractometry has been proposed as a farm technique to estimate the IgG concentration in colostrum. In order to validate the method in goat colostrum using a clinical refractometer, 216 colostrum and milk samples were obtained from 54 dairy goats. Samples were evaluated for protein concentration using a clinical refractometer and IgG concentration was measured using a commercial ELISA. The r² for the linear regression between refractometry value and IgG concentration measured by ELISA was 0.79, and the area under the receiver operating characteristics curve was 0.99. The proposed cut-off value using the clinical refractometer was 10 mg/mL. At this point, the sensitivity, specificity, negative predictive value, positive predictive value, Youden’s index and accuracy were 100%, 95.19%, 100%, 76.32%, 0.95% and 95.83%, respectively.