Secretion composition during bovine mammary involution and the relationship with mastitis.

1. Bacteriological analysis revealed that 30% of quarters contained coagulase-negative staphylococci, Staphylococcus aureus, Corynebacterium bovis, or streptococci. 2. As involution progressed, somatic cell counts, percent protein, pH, and concentrations of serum albumin, lactoferrin, and immunoglobulin G increased while percent fat, concentrations of citrate, and the citrate to lactoferrin molar ratio decreased. 3. Mammary secretion from infected quarters had significantly higher numbers of somatic cells, percent polymorphonuclear leukocytes, and pH, but lower percentage lymphocytes, fat, and lactoferrin concentrations compared to uninfected quarters. 4. Results suggest intramammary infection altered normal secretion composition during bovine involution and lactogenesis. 5. Lower levels of antibacterial components in bovine mammary secretion during the peripartum period may have reduced the natural defense potential of the gland.