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Use of age and serum gamma-glutamyltransferase activity to assess passive transfer status in lambs
R K Tessman1, J W Tyler, S M Parish
1Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman 99164-7010, USA.
Objective:
To develop an algorithm for predicting passive transfer status of lambs of various ages, using the lamb's age and serum gamma-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.