Use of Livestock Medicines on the Dairy Farm
Table of Contents
The use of livestock medicines on the dairy farm by producers and veterinarians is important for disease prevention and control.
Management practices which prevent disease will reduce the need for drug treatment. Planned animal health and production programs commit the milk producer, the veterinarian and other herd advisors to the implementation of herd management policies which optimize health and production. However, when needed, medicines must be used responsibly.
This factsheet provides recommendations on dairy cattle treatment, product label interpretation, treatment recording and antibiotic residue testing of milk. Information about the storage and handling of livestock medicines can be found on the OMAFRA website.
It is essential to read and understand drug labels to use medications safely and effectively. All livestock medicines bear labels which describe product information, indications for use, dosage, route of administration, warnings and storage instructions.
Product information includes:
Information provided by the label on product usage includes:
All licensed products carry labels with warnings, cautions or precautions about the use of the product. For example, when an antibiotic product is recommended for use in cattle the label may include a warning statement "Warning: Not for use in lactating animals". This means that the product is for use only in non-lactating cattle such as dry cows and heifers. Products licensed for use in lactating cattle will indicate a with-holding time for milk following the last treatment. Products recommended for use in cattle will have a pre-slaughter withholding time on the label. With-holding times for milk and meat will only be valid if the product is used according to label instructions.
Labels may also provide information about disease management or product safety under the "Caution(s)" section. For example, a product recommended for intramuscular administration under directions for usage, may carry a caution that it is "not to be given intravenously" if the product is not safely given by that route. For further interpretation of the cautions, precautions or warnings on a product label consult your veterinarian.
Inserts included with many products provide additional information such as side effects which may occur following product use in some animals. The inserts may contain scientific and medical terms which require interpretation by a veterinarian. Carefully read and understand all insert information before using the product.
Veterinarians must meet the same labelling requirements when drugs are dispensed in non-original containers. Information must be provided which identifies the product, the species and class of animals on which the product is to be used, directions for use and with-holding times. As well, the label must carry the name of the veterinary clinic and the veterinarian prescribing the product.
Drug labels are only useful to those who read them. Make a habit of reading the label before every use of a livestock medicine.
"Extra-label" drug use is the use of a drug in any manner other than that listed on the label. Examples of extra-label use include:
Extra-label drug use is permitted only under the supervision of a veterinarian. The with-holding time given on the medicine label does not apply when a drug is used in an extra-label manner. The veterinarian advising extra-label use of a livestock medicine is responsible for recommending a proper with-holding time for milk and meat.
Livestock medicines are an important tool in the treatment and prevention of disease. Correct treatment methods assure the safety of food products and insure an effective response to treatment.
Consider the following points before treating dairy cattle.
Selection of cases: Medication is not always the best option for controlling animal disease. Treat animals based on the diagnosis, the expected response to therapy and the economic benefit expected. For example, viral infections do not respond to antibiotic therapy while those caused by bacteria will. Treating subclinical mastitis at dry off is effective and economical while treating cows with subclinical mastitis during lactation may not be. Select suitable cases to treat with the help and advice of the veterinary practitioner.
Medicine selection: Select the correct therapy. Consult your veterinarian for advice on the correct medication, the route of treatment, the treatment dosage, the time between treatments and the number of treatments. Veterinarians should leave clear written instructions with the herd owner identifying the treated animal and giving information on the treatment protocol. The veterinarian also plays an important role in monitoring the response to treatment.
Treatment method: Treatment must be given correctly to be effective and to prevent complications. Use the following guidelines to develop good treatment habits.
Dosage calculation: To calculate the correct dosage you must know the weight of the animal and the dosage rate. For example, to treat a 600 kg cow with procaine penicillin at the label dosage of 2.5 mL per 100 kg of body weight once daily, inject: 600 kg/100 x 2.5 mL = 15 mL.
One millilitre (ml) and one cubic centimetre (cc) represent the same volume and are interchangeable in calculating drug dosages.
Repeat treatments: Determine the number of treatments to be given from the product label or as recommended by the veterinarian. The duration of treatment should result in a cure without risk of relapse, yet be short enough to insure withholding times are not extended.
Withholding times: Withholding times for milk and meat are given on product labels. A withdrawal day is a full 24 hours starting after the time of treatment. A 48 hour withdrawal time for milk is illustrated in Figure 1.
Figure 1. Diagrams illustrating how a 48 hour milk discard time should be calculated. One shows the number of milkings to be discarded and the other the discard time in hours.
Errors in calculating withdrawal times of only a few hours could result in a residue violation. Label withdrawals are not accurate if products are used in an extra-label fashion, if drugs are used in combination (for example intramammary and intramuscular treatments for mastitis given at the same time), or if the treated animal is severely sick and unable to clear the drug from its body at normal rates. In these cases you must test the milk before addition to the bulk tank to insure it is residue free.
Prevent residues: Simple management practises will prevent contamination of milk or meat. To prevent residues:
Many antibiotic residue violations result from failure to: identify treated cows, maintain treatment records, and use proper milk withholding times. The record system must make all staff involved in milking aware of treated cows and the period for withholding milk from sale. Identify treated cows in a manner clearly visible to the person milking. Some methods used are:
In larger herds identification may be colour coded to show the last day to withhold milk. In tie-stall barns where cows always occupy the same stall, coloured tape or tags attached to the milk inlet of the pipeline can identify a treated animal (Figure 2). Re-enforce cow identification systems with a prominent chalk board or bulletin board in the milking parlour or barn entrance. The identity of all treated cows and the date and time of the last milking withheld should be clearly visible (Figure 3). Train all staff involved in milking to refer to this board immediately before each milking.
Keep a permanent, detailed treatment record for reference and management purposes. Write this in the herd health book or in the individual cow record files. This record should identify the animal, the product and dosage administered, the date of treatment and the milk withholding period (Table 1). Before shipping any animal for slaughter, check this record to insure pre-slaughter treatment withholding requirements are met.
Figure 4. Example of box top file.
In addition, store product inserts and packaging from all livestock medicines in a file folder. This "box top file" (Figure 4) will provide additional information if questions about previous treatments arise.
The persistence of antibiotic residue in milk of treated cows may vary in amount and duration of time present. This may depend on the cow, her metabolism, the medicine type, the use of a combination of medications, the dosage of medication and the method of administration. Test milk suspected of contamination using antibiotic test kits. Examples of these situations where milk contamination may occur include:
A variety of kits are commercially available. When selecting a test kit the user should recognize that kits vary in the type of antibiotics and amount of antibiotic they detect. No single kit can detect all commonly used antibiotics. Confirm that the kit you use "matches" the antibiotic you need to detect.
Milk producers who are comfortable using these tests are encouraged to purchase a test kit for on-farm use. Antibiotic testing services may also be available from veterinarians, milk processing plants, and others.
All unmarketable milk must be disposed of in a manner which protects the environment and keeps drug residues out of all food products. Do not feed milk from treated cows to calves. Milk from treated cows cannot be used in a sour colostrum program since antibiotics prevent normal fermentation. Do not feed milk from treated cows to bull calves or other livestock which may be sold or slaughtered before they are residue free.
Milk from treated cows can be added to a liquid manure storage, or along with straw to absorb it, to a solid manure storage. Do not add milk containing antibiotic to milk house wash water entering a septic tank or treatment trench system. Milk solids will plug the trench tile.
The ultimate responsibility for insuring a milk supply free of drug residues lies with the milk producer. Use of livestock medicines is a privilege which livestock owners cannot afford to abuse. Correct usage of livestock medicines, recording of treatments, and clearly identifying treated cows are essential practises.
Review the use of livestock medicines on your farm. Use the recommendations of this factsheet to revise procedures to insure the safety and well-being of livestock, the dairy industry and of consumers of dairy products.
Additional sources of information include:
For more information:
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