STARTER CULTURE, TEMPERATURE, AND ANTIBIOTIC RESIDUE IN FERMENTATION OF MASTITIC MILK TO FEED DAIRY CALVES

Starter culture, temperature, and antibiotic concentration affecting fermentation rate of mastitic milk were studied to determine if mastitic milk could be preserved to feed dairy calves. In trial 1, milk samples from cows treated with 100,000 IU penicillin G and 150 mg neomycin sulfate in two quarters each were either inoculated with a Streptococcus cremoris-Streptococcus lactis starter culture or allowed to ferment naturally. This was to determine if mastitic milk could be fermented adequately under farm conditions where starter cultures might not be readily accessible. Milkings 1, 3, and 5 postantibiotic treatment required 113, 49, and 43 h to ferment to a pH of 4.7 without culture compared to 114, 17, and 11 h with culture. In trial 2, mastitic milk samples from cows treated with 100,000 IU penicillin G and 150 mg neomycin sulfate, mastitic milk from cows not treated with antibiotics, and normal milk from the bulk tank were inoculated with commercial buttermilk and fermented at 4.4, 21.1, and 32.2 C. Increasing temperature from 4.4 to 21.1 to 32.2 decreased time to ferment to pH 4.7 from 108 to 51 to 38 h. In trial 3, mastitic milk samples from cows treated with 100,000 IU penicillin G and 150 mg sodium novobiocin were inoculated with commercial buttermilk and fermented. Penicillin concentrations in mastitic milk greater than .06 IU/ml and/or novobiocin concentrations greater than .35 µg/ml reduced fermentation rates of milk from postantibiotic treatment milkings 1 and 2. Novobiocin was not detected, and penicillin concentrations had decreased to .02 IU/ml by the third milking. © 1979, American Dairy Science Association. All rights reserved.