Prediction of serum IgG(1) concentration in beef calves based on age and serum gamma-glutamyl-transferase activity

This study examined the relationship between serum gamma-glutamyl-transfera se (GGT) activity and passive transfer status in beef calves less than 18 d ays of age. Immunoglobulin G(1)(IgG(1)) concentrations were measured in 69 commercial beef calves between the ages of 24 and 72 hours. GGT activities were then measured in these same calves at various ages between 3 and 18 da ys of age. Models were developed predicting serum IgG, concentration as a f unction of calf age and serum GGT activity. Minimal association was present between initial serum IgG, concentration and serum GGT activity when all c alves less than 18 days of age were considered (r(2) = 0.065). When the stu dy population was restricted to calves less than 18 days of age, the fit of the developed model was greatly improved (r(2) = 0.438). Serum GGT activit y has no apparent advantage relative to other assay procedures for predicti ng passive transfer status in beef calves. If serum GGT activity is to be u sed to assess passive transfer status in beef calves, application of this p rocedure should be restricted to calves less than 8 days of age.