Use of age and serum ɣ-glutamyltransferase activity to assess passive transfer status in lambs

Abstract

Objective To develop an algorithm for predicting passive transfer status of lambs of various ages, using the lamb's age and serum ɣ-glutamyltransferase (GGT) activity. Design Prospective study. Animals 51 Suffolk, Columbia, and crossbred lambs from 1 to 16 days old. Procedure Serum was obtained from all lambs. Serum GGT activity was measured, using a commercially available kit. Serum IgG concentration was determined by use of radial immunodiffusion. Day-1 serum IgG concentration was estimated from sample IgG concentration, lamb age, and the published 14-day half-life of IgG in lambs. Stepwise multivariate regression models were developed to estimate day-1 serum IgG concentration as a function of the natural logarithm of serum GGT activity (In[GGT]) and natural logarithm of lamb age (In[age]) at the time of sampling. These regression models were then used to calculate serum GGT activities that were equivalent to various day-1 IgG concentrations in lambs of various ages. Results In(GGT) and In(age) were significantly associated with estimated day-1 IgG concentration. Day-1 serum IgG concentration could be predicted using the formula: IgG = −7,686 + 1,366(In[GGT]) + 1,199(In[age]). The model was moderately accurate in predicting serum IgG concentration (R2 = 0.52). Clinical Implications Serum GGT activity can be used to assess passive transfer status of lambs. (J Am Vet Med Assoc 1997;211:1163–1164)