Objective—To determine sensitivity and specificity of
a cow-side immunoassay kit for assessing IgG concentration
Animals—76 dairy and 11 beef cows of various parities.
Procedure—Colostrum from first, second, and third
milkings and milk samples were collected, and IgG
concentration was determined by means of radial
immunodiffusion. The immunoassay was performed
according to the manufacturer’s instructions, and
sensitivity and specificity were calculated by comparing
results of the immunoassay (positive vs negative)
with results of immunodiffusion (< 50 g/L vs
≥ 50 g/L).
Results—135 colostrum or milk samples were collected.
Mean ± SD colostral IgG concentrations,
determined by means of radial immunodiffusion for
dairy and beef cows were 65.4 ± 51.4 g/L and 114.8
± 42.7 g/L, respectively. Mean IgG concentrations
for first-, second-, and third-milking colostrum samples
and for milk samples were 92 ± 49.0 g/L, 74.6
± 45.1 g/L, 47.5 ± 32 g/L, and 6.8 ± 3.8 g/L, respectively.
Sensitivity of the immunoassay (ie, percentage
of samples with IgG concentration < 50 g/L
with a positive immunoassay result) was 93%, and
specificity (ie, percentage of samples with IgG concentration
± 50 g/L with a negative immunoassay
result) was 76%.
Conclusions and Clinical Relevance—Results
suggested that the immunoassay kit was an
acceptable cow-side test to identify colostrum
samples with IgG concentrations < 50 g/L. The
immunoassay kit should be useful in screening
colostrum for adequate IgG concentration before
feeding to calves or storage. (J Am Vet Med Assoc 2005;227:129–131)