The total protein and immunoglobulin profile of equine colostrum and milk

Thirty-six samples of colostrum and milk were collected from ponies at various intervals after parturition. Levels of total protein and immunoglobulins IgG and IgG(T) were determined. In samples collected in the first 3 hours post partum , the total protein concentration was approximately twice that of serum protein and the immunoglobulins IgG and IgG(T) accounted for 30 per cent and 10 per cent respectively of this protein. The ratio of IgG to IgG(T) was similar to that in serum. After suckling, a marked decline in both total protein and immunoglobulin concentration occurred. In addition, the relative concentration of immunoglobulins declined. Thus, IgG and IgG(T) made up 7 per cent and 2 per cent respectively of the total protein in samples collected 9–24 hours post partum . In all samples examined up to 33 days post partum the concentration of IgG (γ 2 ) was approximately three times the concentration of IgG(T) (γ 1 ). Thus no evidence was found for a selective secretion of a γ 1 immunoglobulin in equine colostrum or milk.