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Virginia Cooperative Extension - Knowledge for the CommonWealth

Is extra-label use of mastitis treatment justified?

Dairy Pipeline: May 2002

Gerald M. (Jerry) Jones
Professor & Extension Dairy Scientist,
Milk Quality & Milking Management
(540) 231-4764

Scientists (J.E. Hillerton and K.E. Kliem) at the Compton Institute of Animal Health in the United Kingdom concluded that certain extended, or extra-label, use was most effective in curing clinical mastitis caused by Streptococcus uberis (a common environmental pathogen that causes 35% of clinical mastitis in U.K.). Their results were published in the April issue of the Journal of Dairy Science. They claim that the use of antibiotics to treat mastitis is double the approved level because of the ineffectiveness of recommended protocols. In their research, they infused Strep. Uberis into two quarters of cows and then evaluated the effectiveness of 7 different treatment possibilities, including: label recommendation intramammary at every second milking for 3 days, aggressive extra-label intramammary treatment at every milking for 3 days, intramuscular injection every second milking for 3 days, oxytocin every milking for 3 days, combinations of these treatments, and no treatment. The overall bacteriological cure rate was lowest with label intramammary treatment in the udder, while the highest cure occurred with extra-label intramammary infusion. There was no benefit of using intramuscular treatment with antibiotic or oxytocin, either alone or in combination with intramammary treatment. They concluded that the extra-label intramammary treatment was the most effective and the cheapest with the least amount of antibiotic used. In this manner, the antibiotic is available more quickly and the sooner a quarter is cured of clinical mastitis, the higher the bacteriological cure rate. In the UK, extra-label use requires that milk be discarded for at least 7 days and meat for 28 days after the last treatment with this antibiotic. The authors recommended that milk be discarded until it is tested negative for inhibitory substances (drug residues). From an antibiotic resistance point of view, the extra-label treatment might be more desirable because of higher cure rates and fewer resistant bacteria surviving.

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