Proper sample handling is critical for accurate mold and mycotoxin analysis. When shipping samples, eliminating oxygen and cooling the sample will help conserve the sample integrity.
The recommended methods to properly preserve a sample for shipping are:
Vacuum-sealed. Inexpensive Food Saver® or Ziploc® sealing systems will work well for vacuum-sealing mold and mycotoxin samples.
Keep sample cool! Cooling provides additional protection for multiple day or weekend shipments. Cold packs can be included in shipments but should not be in direct contact with the sample. Be sure samples are not allowed to freeze as this may result in erroneous mold, yeast, and toxin counts.
Aflatoxin contamination in milk is strictly regulated and is directly proportional to the concentration of aflatoxin in the feed.
Bear in mind that aflatoxin is not uniformly present throughout a feedstuff and improper sampling can result in large analytical variation.
To illustrate this problem consider:
Within a contaminated ear of corn, kernels typically contain 0 - 400,000 ppb aflatoxin.
One single kernel contaminated with 400,000 ppb aflatoxin causes an overall contamination concentration of 26 ppb in a 10-pound sample.
20 individual samples from a load of contaminated cottonseed often range from 15 to 160 ppb with an average of 74 ppb.
Proper feed sampling, along with accurate testing, is crucial in determining aflatoxin risks in herd health.
Take ½ gallon samples from each load of feed as it is flowing into the bin
Avoid sampling from the very beginning and the very end of each load
Composite several samples and mix thoroughly
Sampling stored feed can be challenging. Use caution and care when
pulling samples and follow these recommendations:
For sampling instructions of grain in trucks, railcars, and storage bins, download The USDA Grain Inspection Sampling Handbook from http://www.gipsa.usda.gov/publications/fgis/handbooks/gihbk1_insphb.html
When sampling horizontal bunkers:
Use a face shaver to shave silage from the entire vertical and
horizontal face of the feed-out surface.
Load the silage into a TMR mixer and mix for 2-5 minutes
Unload the silage and take 12 or more “grab” samples from throughout the pile
Vertical silos and silage bags are extremely difficult to sample after filling. Contaminated areas of the field are likely to be concentrated in small areas of the silo.
*Take great caution when interpreting results from samples taking at feed out from these storage structures.
Subsampling is often required to reduce samples to a reasonable size for shipping. Maintaining sampling accuracy is best done by using the coning and quartering technique for most feedstuffs. This can be accomplished by:
Form the sample into a cone by pulling the sample from the bottom edges to the top center of the sample.
Flattening the cone
Divide the cone into quarters
Discard opposite corners to reduce the sample size
Repeat as needed to obtain the desired sample size.