Endotoxin levels in milk and plasma of mastitis-affected cows measured with a chromogenic limulus test

Abstract

A chromagenic limulus test (“Toxicolor”) was applied to cow's milk and plasma after treatment with perchloric acid to remove interfering factors. The endotoxin levels in normal cow's milk and plasma were all <10 pg ml −1. In acute mastitis, the milk endotoxin level averaged (1.1 ± 0.7) × 10 3pg ml −1 in the cases where Gram-negative bacteria were isolated, while the plasma endotoxin concentration was normal. The endotoxin levels in the quarters infected with Gram-positive bacteria were all normal, both in milk and plasma. In gangrenous mastitis due to Gram-negative bacteria, the endotoxin concentration was very high in both milk [(9.3 ± 5.3) × 10 6pg ml −1] and plasma (85.2 ± 68.2 pg ml −1). In similar cases due to Gram-positive bacteria, endotoxin levels were all normal, both in milk and plasma, resembling the acute mastitis due to Gram-positive bacteria. The test was considered suitable for the diagnosis of mastitis due to Gram-negative organisms and the levels of endotoxin detected would aid in assessing the prognosis.