Effect of Milking Without Pulsation on Teat Duct Colonization with Streptococcus agalactiae and Penetrability to Endotoxin

¹ Agricultural and Food Research Council, Institute for Animal Health, Compton Laboratory, Compton, Newbury, England RG160NN
² Mastitis and Milk Secretion Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705

Forty quarters of 10 cows were milked for a 9-d period with one of four treatments: 1) no liner pulsation, 2) conventional milking, 3) no pulsation for 4 d followed by conventional milking for 5 d, and 4) conventional milking for 4 d followed by milking without pulsation for 5 d. All teat orifices were inoculated with approximately .5 million cfu of Streptococcus agalactiae and Streptococcus dysgalactiae on d 1 and 5. Recoveries of Strep. agalactiae from the teat end were increased for teats milked without pulsation. Recoveries of Strep. dysgalactiae were lower than those of Strep. agalactiae and not increased by milking without pulsation.

In a second experiment, teats of 20 cows were milked for a 15-d period with or without liner pulsation. For 10 successive milkings, all teats were inoculated with 1.0 µg of Escherichia coli endotoxin either immediately or 2.5 h after each milking. The frequency of endotoxin penetration, measured by the Wisconsin Mastitis Test, in pulsated quarters and in nonpulsated quarters was similar. For quarters milked without pulsation but not for pulsated quarters, inoculation of endotoxin immediately after milking led to greater incidence of teat duct penetration than for inoculation 2.5 h after milking.

Key Words: mastitis • streptococci • pulsation

Submitted on May 25, 1990
Accepted on March 11, 1991