Determination of IgG levels in bulk ewe's milk

Colostrum addition to milk results in a reduction of the yield during cheese manufacturing. Determination of IgG levels is accepted as an evidence of this troublesome habit due to the high level of this protein in colostrum. This study shows for the first time the IgG levels in bulk ewe's milk samples from Spain throughout the year. IgG quantification was carried out by a sandwich ELISA that recognizes specifically ovine IgG. The mean value of IgG concentration obtained from 481 samples was 0.271 ± 0.253 mg/ml. In general, this value is within the range considered acceptable for mature milk according to quality payment systems. Surprisingly, a high mean concentration was obtained in samples collected in winter, 0.742 ± 0.378 mg/ml, suggesting that births were grouped in that period. These results point up that standardization of ewe's milk production has not been achieved yet. For this reason, determination of immunoglobulin levels periodically would be a good parameter to control milk quality.