Assay of penetrability of bovine papillary duct implanted with Escherichia coli endotoxin.

A method has been developed to assay the relative penetrability to a solute of the papillary duct (streak canal) of the bovine teat. Escherichia coli lipopolysaccharide endotoxin (1.0 microgram in 2.5 microliter of sterile distilled water) was implanted at a depth of 3 mm from the distal end (papillary orifice) of the papillary duct. If penetration by the irritant occurred after any one of 5 successive daily implantations, the inflammatory response of the mammary gland was detected by a precipitous increase (by at least 15 mm) in the Wisconsin mastitis test score of quarter foremilk samples, and the test was scored as positive. Results of the penetrability assay were highly repeatable among quarters of certain cows. Cows differed as to the pattern of penetrability of their papillary ducts, with about half of 70 tested cows scoring 4 positive or 4 negative.