Use of Livestock Medicines on the Dairy Farm

Agdex#:	410/662
Publication Date:	03/92
Order#:	92-056
Last Reviewed:	09/96
History:	New
Written by:	Ann Godkin - Health Management Veterinarian/OMAFRA; Jack Rodenburg - Dairy Cattle Specialist/OMAFRA

Table of Contents

1. Introduction
2. Labeling
3. Extra-label Drug Use
4. Drug Treatment
5. Treatment Records
6. On-Farm Antibiotic Testing
7. Disposing of Milk From Treated Cows
8. Summary
9. Drug Handling Check List
10. Related Links

Introduction

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 in the Factsheet "Storage and Handling of Livestock Medicines on the Dairy Farm", Agdex 410/662.

Labeling

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:

• the product name ("brand name"),
• the name of the manufacturer or distributor,
• the drug identification number (D.I.N.),
• the manufacturers lot number,
• the active ingredient in the product, and
• the concentration of active ingredient.

Information provided by the label on product usage includes:

• the indications for medicine use, such as:
• the species (cattle, horses, swine)
• the class of livestock (lactating cows, nonlactating cows, calves) and,
• the disease conditions (mastitis, foot rot, metritis),
• the directions for medicine use, such as
• the dosage (how much, how often and for how long), and,
• the method of administration
  • intramuscular - into the muscle,
  • subcutaneous - under the skin,
  • oral - by mouth,
  • intramammary - into the udder through the teat end,
  • intrauterine - into the uterus,
• storage requirements such as refrigeration, and
• the expiry date, the date past which the product should not be used.

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 labeling 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

"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:

• using a product to treat a lactating cow when the label does not list lactating dairy cattle
• using a product at a higher dosage than that listed on the label,
• using a product labeled for intramuscular injection as a subcutaneous injection, and
• using a drug to treat mastitis when the label recommends it only for use in the treatment of respiratory disease.

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.

Drug Treatment

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

Drug treatment is not always the best option for controlling animal disease. Treat animals based on the diagnosis, the expected response to treatment 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 during lactation may not be. Select suitable cases to treat with the help and advice of the veterinary practitioner.

Drug 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.

• Wash your hands before and after handling livestock medicines.
• Use proper equipment: Choose the correct syringe and needle size for the dosage and the type of injection to be given.
  • For intramuscular injection use a I 1/2", 16 or 18 gauge needle to insure the drug goes in the muscle and not under the skin. Before injecting, pull back on the plunger to insure the needle tip is not in a blood vessel. Select appropriate injection sites with the help of your veterinarian. Read the label for the maximum amount to be injected in one site.
  • For subcutaneous injection use a 1/2" to 1", 16 or 18 gauge needle. Check that the needle tip is moveable. Inject a small amount of drug to see if a "bleb" of skin starts to rise in the area of the needle tip. This will verify that the needle is under the skin and not in the muscle. Inject only in sites recommended by your veterinarian.
• Inject only in clean body sites.
• Use clean equipment. Single use, sterile, disposable needles and syringes are preferred.
• Give repeated injections in different body sites.
• Before infusing antibiotics into the udder, wash and dry your hands and the teat with single use paper towels. Disinfect the teat end with the alcohol swab provided in the medication package. Avoid touching the infusion canula at the end of the treatment tube. Use only single dose infusion products in disposable syringes. Teat dip the teat after infusion of medication.

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 milliliter (ml) and one cubic centimeter (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 practices will prevent contamination of milk or meat. To prevent residues:

• record all treatments given;
• mark all treated cows;
• inform all people involved in milking of treated cows;
• milk treated cows last or use separate "bypass" equipment to insure that no contaminated milk enters the milk supply;
• discard milk from all quarters of treated cows;
• discard milk from all cows calving within 30 or 42 days of dry treatment according to label directions;
• discard milk from fresh cows for the required period if dry treatment was used;
• use antibiotic test kits as needed;
• and follow label directions for all medications used. These include feed additives, medicated feeds such as calf starter, topical preparations, as well as injectable and infusion products.

Treatment Records

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:

• leg bands,
• coloured tape or fluorescent hockey tape around the legs or tail, or
• paint markings on the cow's flank, rump or legs.

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). Reinforce cow identification systems with a prominent chalk board or bulletin board in the milking parlour or barn entrance. Walls constructed of "white board" designed to be written on with special markers are an excellent way to create a very large bulletin board. 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.

Figure 2. Clearly visible identification of treated animals such as leg bands (left) or tags on the pipeline (right).

Figure 3. Example of Bulletin Board identifying treated cows clearly visible to milking staff.

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.

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.

Figure 4. Example of box top file.

 

Table 1. Treatment Record Example

Cow Identity:
Date	Diagnosis	Treatment	Dosage	Duration of Treatment	Label Withdrawal (No. of milkings)	Date Tested	Milking Returned to Tank

On-Farm Antibiotic Testing

The persistence of antibiotic residue in milk of treated cows may vary. 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:

• the addition of purchased milking cows to the herd for which the treatment history is unknown,
• fresh cows purchased during their dry period who have unknown dry off dates or dry treatment histories, cows treated in an extra-label manner, cows treated with more than one product, cows which are severely ill at the time of treatment,
• cows which calve before the end of the milk withholding time following dry treatment,
• establishing the identity of a treated cow when an error in identification may have occurred, and
• the testing of milk in the bulk tank when contamination with milk containing medication may have occurred.

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. Before selecting a test kit confirm with your Ontario Ministry of Agriculture and Food,

Dairy Inspection Branch field person that the kit is comparable in sensitivity to official tests. For the penicillin group of antibiotics the "Delvotest P" is easy to read and detects these drugs at levels similar to the official test.

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. Local staff of the Dairy Inspection Branch have current information on test kits and are also available to conduct a field test on request.

Disposing Of Milk From Treated Cows

All unmarketable milk must be disposed of in a manner which protects the environment and keeps drug residues out of all food products. Milk from treated cows can be fed to replacement dairy calves older than 6 weeks of age without harm. Do not feed variable or abnormally large amounts of milk to calves to dispose of it. 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.

Summary

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 practices.

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.

Drug Handling Check List

Drug Labeling

• All products are clearly labeled
• All labels are read and understood

Treatment Practices

• Treatments given as recommended by a veterinarian
• Products used only as recommended on the label, unless a veterinarian has provided written directions to do differently
• Appropriately sized equipment is used to give treatment according to route of treatment
• Single use, sterile needles and syringes are used
• Proper injection sites are used
• Intramammary treatments are infused correctly
• Dosages are routinely, calculated correctly

Treatment Records

• Treated cows are always clearly identified
• Treatments are recorded in individual cow records and on a blackboard or bulletin board
• Staff are instructed in record use
• "Boxtop file" of product inserts and packaging is kept

Residue Avoidance

• All milk from all quarters is withheld for full withdrawal period
• Treated cows are milked last
• Milking equipment is cleaned after milking treated cows

Antibiotic Testing

• Antibiotic test kits are used according to directions
• Milk is routinely tested if from:
  • cows treated in extra-label fashion
  • purchased cows
  • sick cows
  • dry cows calving early

Additional Information

Additional sources of information include:

1. Storage and Handling of Livestock Medicines on the Dairy Farm, Agdex No. 410/662
2. Canadian Compendium of Veterinary Pharmaceuticals, Biologicals and Specialties, 2nd Edition 1991. CCVPBS, 148 King St., P.O. Box 39, Hensall, Ont. NOM IXO.
3. Recommended Code of Practice for the Care and Handling of Dairy Cattle, 1990. Agriculture Canada Publication 1853/E.

Related Links

• Storage and Handling of Livestock Medicines on the Dairy Farm