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Fermentation of Mastitic Milk from Antibiotic Treated Cows¹

Animal Physiology and Genetics Institute, Agricultural Research Center, USDA, Beltsville, MD 20705

ABSTRACT

Effects of antibiotics on the rate and extent of fermentation of mastitic milk were sought. Normal milk, colostrum, mastitic milk from cows not treated with antibiotics, and mastitic milk samples from antibiotic treated cows (100,000 IU penicillin G and 150 mg neomycin sulfate/one quarter each) were obtained from weigh jars during three consecutive morning milkings (four cows/treatment), inoculated with a commercial lactic starter culture, and fermented as individual-cow milkings. A drop in pH to 4.7 within 24 h was the indicator of satisfactory fermentation. Normal milk required 15 h, colostrum 49 h, untreated mastitic 29 h, and treated mastitic 53 h to reach a pH of 4.7 when averaged across milkings. Because milking sequence seriously affected treated mastitic milk, fermentation samples were collected from four additional antibiotic-treated mastitic cows during the first six consecutive postantibiotic-treatment milkings and fermented as before. Postantibiotic treatment milkings 1, 2, 3, 4, 5, and 6 required 100, 73, 23, 17, 12, and 10 h to reach a pH of 4.7. Antibiotic concentration in mastitic milk declined to permit satisfactory fermentation by the third postantibiotic-treatment milking.

¹ This research was a part of Regional Research Project NC-119, Improving Large Dairy Herd Management Practices.