Chapter 5 - Sampling and Testing

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5.2 Chemical Residues

5.2.9 Sulfonamides

5.2.9.1 Introduction

Sulfonamides are used primarily in the prophylaxis and therapy of bacterial diseases. In combination with antibiotics, notably of the tetracycline and penicillin group, they are widely employed as medicated feeds to increase the rate of weight gain in livestock.

In hogs, these compounds serve as an aid in maintaining growth rate and feed efficiency in the presence of atrophic rhinitis, and in the prevention of bacterial enteritis, including salmonellosis (Salmonella enterica) and swine dysentery.

In beef cattle, sulfonamides are used to maintain weight gain and feed efficiency during periods of stress due to weaning, shipping or handling.

In poultry, sulfonamides form a valuable aid in preventing or in reducing mortality due to coccidiosis, fowl typhoid and acute fowl cholera.

Injectable and bolus sulfonamides may be administered alone or formulated in combination with a synergist such as trimethoprim. Such products may contain more than one sulfa.

Sulfonamides may therefore be administered to a single animal, or as a mass medication. Only sulfamethazine is licensed for use as a medicated feed ingredient. Sulfaquinoxaline may be administered to poultry via water.

The rationale for testing dressed carcasses and organs for sulfonamide residues is largely analogous to that of antibiotics.

Rapid screening for sulfamethazine in market hogs is performed using the Kidney Inhibition Swab (KIS) test manufactured by Charm Sciences Inc.

5.2.9.2 Sample selection

Sampling frequencies for the KIS test are set for each establishment by the National Manager, Chemical Residues. The frequency specifies how many tests are to be performed per week, and how many are to be performed in each batch.

If samples are not being taken every day, avoid falling into a pattern, such as testing only on certain days of the week, or every second day. Also avoid taking samples only at certain times of the day. This is to prevent producers from evading testing by predicting when it will occur.

Animals should be selected from different truckloads or sale lots. Since sulfonamides are normally administered to an entire lot, there is no point in testing more than one animal from a single barn.

5.2.9.3 Testing

The presence of sulfamethazine residues in swine is monitored by the use of the Kidney Inhibition Swab (KIS) rapid in-plant test.

The KIS test is performed in accordance with the procedure described in Meat Hygiene Training Module E-8, PS# I6D252, Version 1 - October 2010. This procedure must be followed exactly. Variations in the technique have not been tested for reliability, so they could result in false test results, and could be challenged in court or by foreign auditors.

All costs associated with sulfonamide testing, including both in-plant screening and confirmatory testing, are to be charged to the establishment. Fees are to be calculated according to Part 10 of the Meat Products Inspection Section, Canadian Food Inspection Agency Fees Notice.

5.2.9.4 Follow-up procedures on positive KIS test

The KIS test is not specific for sulfamethazine, but only detects the presence of microbial inhibitors. Therefore, a positive KIS test cannot be assumed to affect the herdmates.

Laboratory confirmation of presumptive positives is mandatory. One 500g sample of skeletal muscle and 500g of liver must be frozen and shipped to the Centre for Veterinary Drug Residues, Saskatoon accompanied by a completed CFIA/ACIA 5165 form (Meat Product Inspection Sample Submission Form). See section 5.8.3, Samples for chemical residue analysis.

The sample plan number is the fiscal year, followed by an underscore and "M8KIS", for example "2011_M8KIS".

The carcass, viscera, and offal from the test animal must either be held pending laboratory confirmation or treated by the operator as condemned. The condemned carcass and offal may be sent for normal rendering.

5.2.9.5 Follow-up procedures on notification of confirmatory lab results

5.2.9.5.1 Disposition

Upon notification of confirmatory lab results, the following action shall be taken on the tested animal:

* May be sent for normal rendering.

**Case 4 is a rare occurrence that warrants further investigation at the discretion of the National Manager, Chemical Evaluation.

5.2.9.5.2 Pre-testing

Producers who supply animals found to be in violation of the Maximum Residue Limit for sulfonamides will be subject to pretesting. Pre-testing consists of sampling six hogs sent in advance of the next production lot. These animals will be screened by KIS, and if the results are negative the carcasses will be released and the rest of the herd can proceed to slaughter. Any positive test is handled in the same manner as described in section 5.2.9.4 above.

Viscera from pre-test animals can be sent for inedible rendering, regardless of the presence of residues.

Where they exist, provincial Marketing Boards will advise inspection personnel and management of the establishment when pre-test animals are being shipped. A minimum period of ten days must have expired from the date of the violation before pre-test hogs can be presented for slaughter, in order to allow time for the animals on farm to clear the drug.

Violative results obtained while on pretest will require a submission of a further set of pre-test hogs upon the expiration of a minimum of ten days following the date of the previous submission.

5.2.9.5.3 On-farm inspection

In all cases of violative residues, an on-farm inspection is conducted by animal health or feeds inspectors.

5.2.9.6 Company testing

Some companies perform considerable Sulfa On Site testing in order to meet customer requirements.

If the company uses a screening test other than KIS, it cannot substitute for CFIA's testing program. Results of the company's testing shall be made available to CFIA inspectors in accordance with Section 13(1) of the Meat Inspection Act. The company's HACCP plan should describe what action the company will take in the event of a positive test.

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