Comparison of turbidometric immunoassay, refractometry, and gamma-glutamyl transferase to radial immunodiffusion for assessment of transfer of passive immunity in high-risk beef calves.

Within this cohort of calves, TI demonstrated the best correlation with RID; however, significant bias was identified which led to frequent underestimation of IgG concentration. Serum total protein demonstrated less correlation with RID but had less misclassification than TI. Both TI and TP demonstrated less correlation for calves that received colostrum replacement prompting clinical awareness of colostrum type when evaluating individual TPI in beef calves.