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Virginia Cooperative Extension - Knowledge for the CommonWealth

Reducing Milk Losses Following Penicillin Use In Lactating Dairy Cows

Dairy Pipeline: April 2008

John Currin, Extension Dairy Veterinarian
(540) 231-5838;

Penicillin is an antibiotic commonly used in lactating dairy cows. It was approved many years ago and the label calls for a dose of 1cc/100 pounds of bodyweight once a day. At this dose the label recommendation is 48 hours for milk withdrawal and 10 days for slaughter withdrawal.

Current recommendations are much higher than those doses found on the label. Veterinarians commonly recommend doses of 3-5cc/100 pounds of bodyweight once or twice a day. Such doses lead to prolonged withdrawal times which in turn require much more milk to be discarded. These extended withdrawal times have long been a source of frustration for farmers. Often, the most expensive component of treating a lactating dairy cow is the cost of the discarded milk (see table 1).
Table 1
Table 1

FARAD (Food Animal Residue Avoidance Database) is a government sponsored organization that reviews scientific data and makes recommendations for appropriate withdrawal times for drugs that are used in an extra-label manner. In order to reduce the extended withdrawal times seen in cows treated with extra-label doses of penicillin FARAD makes the following recommendations based on a review of the scientific studies:

Giving Penicillin subcutaneously (SQ) or injecting larger volumes per injection site results in prolonged milk withdrawal times. Because of the expense associated with shipping adulterated milk I still recommend that farmers test milk with an on-farm test at 4-5 days after the last treatment before putting milk from the treated cow back in the tank.

Following the above recommendations will help eliminate unnecessary extended withdrawal times of 7-14 days. Use of penicillin at doses greater than those found on the label represents extra-label drug use and should only be used by or on the advice of a licensed veterinarian.

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