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Toxicology / Nutrition

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Toxicology/Nutrition Submission Guidelines

The purpose of the diagnostic toxicology section is to provide consultation, suggestions, and interpretation regarding suspected toxicoses. This consultation includes information about specific samples or specimens useful in confirming diagnoses suspected by the attending clinician. To best accomplish this, a thorough interchange of information between clinician and diagnostician is important. A written or telephone history from the attending veterinarian is useful if the analyses are to be suggested by the toxicologist. A complete account of history (including management and feed type), clinical signs, and lesions submitted with specimens for laboratory evaluation is very important. Currently, the practice of diagnostic toxicology requires that specific analyses or chemical categories be selected. There is no practical or affordable way to check for all possible poisons. The more information provided, the more efficient and useful is the selection process.

The VDL offers services for nutritional monitoring through analysis of feeds, serum and liver for minerals and selected vitamins. Water quality analysis is also available. The VDL does not perform proximate analysis (TDN, protein, etc.) on feeds or forages.

Selecting specimens for toxicology and chemical evaluation requires three main criteria:

  1. The correct specimens must be provided.
  2. Adequate amounts must be available.
  3. Specimens must be properly preserved.

Choice and condition of specimens is extremely important when diagnostic support is required for a suspected toxicology case. The following are guidelines to increase the usefulness of toxicologic submissions.

  1. Specimens should be free of chemical contamination and debris. Contamination of samples with hair, vomitus, dust, dirt, etc., may contaminate the sample and produce erroneous results.
  2. Freeze animal and tissue specimens for chemical analysis and package them to arrive at the laboratory while still frozen. Do NOT freeze whole blood samples, but keep them refrigerated.
  3. Serum, if separated from the clot and not hemolyzed, may be frozen. In some cases, such as analysis for ammonia, this is essential.
  4. Always package specimens from various organs and fluids separately.
  5. Use clean glass or plastic containers that can be tightly sealed.
  6. Label each specimen (container) so it can be clearly identified.
  7. Never add preservative, such as formalin, unless there is a specific reason. If preservatives are added, include a sample of the preservative along with the specimen.
  8. Submit samples for chemical analysis of low level organic contaminants, such as pesticide residues or PCB's, in glass containers (line lids with foil), not plastic. Solid samples for this purpose may be wrapped in aluminum foil.
  9. If ammonia, urea, or cyanide toxicosis is suspected, freeze rumen contents and blood or serum immediately after collection. Keep them frozen.
  10. On all toxicology cases involving a dead animal, submit both fresh and fixed tissues.

Maintaining Package Integrity

In situations where integrity of a package must be maintained for legal or insurance purposes, sealing of the package and transmittal is recommended according to the Federal Bureau of Investigation Guidelines as follows:

  1. Place specimens securely in box.
  2. Seal box.
  3. Place copy of transmittal letter in envelope and mark "invoice".
  4. Stick envelope to outside of sealed box.
  5. Wrap sealed box in outside wrapper and seal with gummed paper.
  6. Address to laboratory, with attention to a specific person if possible.

Tissue Specimens

Analyses are directed toward exposure sites (skin and digestive tract), areas of metabolism and excretion (liver, kidney, urine), and accumulation in specific affected organs or storage sites (e.g., brain, fat, bone).

SPECIMENS TO SUBMIT FROM A LIVE ANIMAL
Milk (if appropriate) 100 ml
Serum (clot removed) 5 ml
Urine 50 ml
Vomitus or feces 200 grams
Whole blood (in anticoagulant) 10 ml

Feeds and Environmental Samples

Sampling error or collection of a non-representative sample is often a weak link in submitting feeds or forages for analysis. General rules for sampling follow:

Grain, mixed feed

  • To prevent condensation and fungal growth during transport, do not ship high-moisture samples unless feed is first dried or frozen. Cloth or paper packaging may be better suited to maintain grain/feed sample integrity during shipping, since plastic bags promote fungal growth.

Forage

  • Sample size for hay and silage should be at least 1 quart. Cut all forages to a length of 3" or less.
  • Pack samples tightly to exclude air, and seal airtight in plastic bags. Very dry samples may be submitted in paper bags.
  • Transport samples to the laboratory as quickly as possible.
  • Take multiple samples from baled or loose hay. A Penn State forage sampler or equivalent core sampling device is recommended.
  • For square bales, sample from the end of the bale the full length of the sampler tube.
  • For round bales, sample across the bale at the center.
  • Take standing pasture and row crop samples from a minimum of 8-10 locations within a field. Remove forage from a four-foot area at grazing height. Mix all collected forage and take a representative sample (500 grams) for analysis.
  • In some cases, it might be advisable to retain larger samples of feed or forage in case feeding of test animals becomes important. For this purpose, a minimum of 5-10 pounds or more may be required depending on the animal desired for experimental feeding. Feeding trials may require a 10-14 day (or more) supply of feed. If a feeding trial or bioassay is desired, please contact the laboratory for further details.

Water

  • Rinse container with the water to be tested prior to collecting the sample to be tested.
  • Submit water samples for inorganic analyses in clean containers of either glass or plastic. Containers should be sterile if microbiologic testing is requested.
  • Submit all water samples for organic analyses in clean glass jars with clean aluminum foil placed over the mouth of the jar before attaching the lid.
  • Transport samples to the laboratory as soon as possible.

Results and Interpretation

The interpretation of the clinical significance of chemical data should be done carefully taking into consideration other evidence presented in the case. Positive chemical findings are not always evidence of intoxication nor are negative findings always indicative that toxicosis did not occur. For example, chlorinated hydrocarbon insecticides may accumulate to high levels in fatty tissues of animals without being associated with clinical signs. On the other hand, organophosphate insecticides rapidly disappear from body tissues and their absence would not guarantee the animal had not been poisoned.

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