IgG concentration in mammary secretions of goats throughout lactation in healthy and coagulase-negative staphylococci infected udders.

Radial immunodiffusion was used to determine immunoglobulin (Ig)-G concentrations in 16 mammary secretions from uninfected udder halves and in 10-14 secretions from halves subclinically infected with coagulase-negative staphylococci in goats throughout lactation. IgG concentrations in samples from uninfected halves decreased rapidly during the first week after parturition (P < 0.001 ), henceforth falling slowly up to 30 d post-partum (P < 0.001). From 30 d post-partum to 180 d of lactation, IgG concentration showed a continuous decline to the end of the experiment but these changes were not statistically significant until 150 d after kidding (P < 0.01). IgG concentrations in lacteal secretions of halves harbouring coagulase-negative staphylococci showed a similar pattern, from the first month of lactation, to that observed in healthy udder halves, but concentrations were always lower. These differences were significant from 2 months after parturition (P < 0.001). IgG concentrations were compared with somatic cell counts obtained using an automatic counter (Fossomatic).