What are the withdrawal periods for drugs given to sheep/goats?


When drugs are given to animals, part of the drug and its by-products wind up in the meat, milk, or eggs. The withdrawal period is the time between the last administration of the drug and the moment when the level of drug residues is deemed safe (acceptable). FDA calls this the "maximum residue limit." A large safety of margin is used to determine withdrawal periods.

Every approved livestock drug has a withdrawal period. It is listed on the label. However, it only applies to use of the drug as specified on the label: species, dosage, route of administration, frequency of treatment, etc. Withdrawal periods are different when drugs are used in an extra label manner, which is common with sheep/goats.

Withdrawal periods are different for different drugs. They also vary according to how the drug was administered (oral, injection, topical) and to which species it was given (cow, pig, goat, sheep). Withdrawal periods are longer for drugs that are adminstered subcutaneously (SQ) versus intramuscularly (IM). They are shorter for drugs that are given orally or applied topically. There are different withdrawal periods for meat and milk. They are usually shorter for milk. Withdrawal periods are often longer for goats, because there is insufficient data. Higher doses of medications require longer withdrawal periods.

Sheep/goat producers are obligated to make sure their animals and their products don't contain illegal residues of antibiotics, dewormers, or other medicines. It is important to keep records of drug use. Violations are subject to penalties. At the same time, sheep/goat producers should strive to minimize the use of drugs by focusing more on disease prevention than treatment.

Antibiotic resistance is a well-known problem. It is problematic in both human and veterinary medicine. While drug residues aren't the major contributor to antibiotic resistance, they are still a factor, and they can cause allergic reactions in people. Antibiotics are medicines used to treat bacterial infections. They shouldn't be used for anything else. They shouldn't be given just because you don't know what is wrong with an animal. Antibiotics are an important tool in livestock production, but they must be used judicously. Most antibiotic use requires veterinarian involvement, and in the future, all will.

****The antibiotic with the shortest withdrawal period is ceftiofur. There are several formulations of this drug: Naxcel®, Excenel®, and Exceed®. The withdrawal period for Naxcel® is only 5 days, 21 days for Excenel®, and 28 days for Exceed®. All of these are prescription antibiotics used to treat various disease conditions. Zactran® (2 ml/100 lbs.) is the antibiotic with the longest withdrawal period: 90 days. Zactran® is a prescription antibiotic that is sometimes used to treat foot rot. Over-the-counter antibiotics Penicillin (3.3 ml/100 lbs.) and LA-200® (4.5 ml/100 lbs., extra label for sheep/goats) have withdrawal periods of 28 and 35 days respectively. The withdrawal period for Nuflur®, another prescription antibiotic, is 42 days (6 ml/100 lbs every 48 hours).

Anthelmintics (dewormers)
Compared to antibiotics, dewormers (anthelmintics) tend to have shorter withdrawal periods. Levamisole (Prohibit®, Leva-Med®) has the shortest withdrawal period (3 days). It clears the animal's system very rapidly. Moxidectin (Cydectin® drench) has the longest withdrawal period (14 days). When these same drugs are used in goats, the withdrawal periods are extended to 4 and 17 days respectively. There is no milk withdrawal for Morantel tartrate; however, its meat withdrawal is the longest at 30 days (for goats).

When different formulations of dewormers are used, the withdrawal periods are affected. When Cydectin® pour-on is given orally to goats (not recommended), the withdrawal period increases from 20 to 23 days (0.5 mg/kg). When it is used as a pour-on (not recommended), the withdrawal period is only 1 day. The withdrawal periods for injectable dewormers are substantially longer than drenches. For example, the withdrawal period for moxidectin injectable (for goats) is 120-130 days (ACSRPC, 2011), compared to only 20-23 days when the drench is used . The withdrawal period for ivermectin injectable (for goats) is 35 days compared to 11-14 days for the drench. Injectable dewormers are not recommended. They may be less effective, and they accelerate dewormer resistance. Stick to the drenches.

It is customary to give higher doses of anthelmintics, especially to goats. Higher doses of the dewormers require longer withdrawal periods. For example, withdrawal periods of moxidectin for goats are 14, 20, and 23 days when the drug is given (orally) at 0.2, 0.4 (4.5 ml/25 lbs), and 0.5 mg/kg of body weight. When you give more than one dewormer at the same, as is recommended for clinically-parasitized sheep/goats, the withdrawal period is the withdrawal period for the dewormer with the longest withdrawal (usually Cydectin®). When dewormers are given on consective days (not recommended), the withdrawal period is calculated after the last dose.

Coccidia drugs
There is a 2 day meat withdrawal for amprolium (Corid®), an extra label but over-the-counter drug commonly used to treat coccidiosis. The withdrawal period for sulfa antibiotics (prescription), also used to treat coccidiosis, is variable. There is no meat withdrawal for Vecoxan® (diclazuril) whereas BayCox® (toltrazuril) has a 48 day meat withdrawal (for lambs). While used in other countries, neither of these drugs are approved in the US. The coccidiostats (Bovatec®, Rumensin®, and Deccox®) have no meat withdrawals. They have short withdrawals for milk, 1-4 days.

Other animal health products
Most vaccines have 21 day meat withdrawals. There is a 14 day meat withdrawal for BO-SE® (selenium, vitamin E) for sheep. Withdrawal periods for some of the other products used for sheep/goats are hard to find, since they are both prescription and extra label. Web sites sometimes have conflicting information since withdrawal periods can vary due to some of the factors already mentioned: species, dosage, route of administration, etc.

The definitive reference for withdrawal periods is FARAD: Food Animal Residue Avoidance Database. Licensed veterinarians may submit requests to FARAD to determine withdrawal periods for the extra label drugs they prescribe. For producers, there is a look-up tool for selected extra label drug uses. Anytime you are unsure of a withdrawal period, you should consult your veterinarian.


Additional reading
Drug residue avoidance in small ruminants
Antibiotic use in sheep production (by Kevin Pelzer, VA-MD College of Vet Med)****
Medications commonly used in goats and approximate withdrawal times
Sheep dewormer chart - American Consortium for Small Ruminant Parasite Control
Goat deworming chart - American Consortium for Small Ruminant Parasite Control