AOCS Feed Microscopy Division Newsletter November 2006
The Feed Microscopy Laboratory Proficiency Program, 2005-2006 Edition.
Annie Fournier
This year marked a new era in the Feed Microscopy Laboratory Proficiency Program (FM-LPP). The electronic reporting system was introduced to, and I must say quickly adopted by, participants. Setting up this electronic system, however, was no small task. Our LPP is like no other the AOCS had ever seen. Other LPPs look to quantify a specified analyte; the participants enter numerical values to specific prompt(s) and voilą, up it goes to a statistical analysis software and there pops out a few numbers that can be linked to reproducibility, accuracy, bias, precision, and let us not forget the new buzz word: uncertainty of measurement.
Forgoing advances in digital imaging and microscope technology, the Feed Microscopy world may be relatively low tech, but is far from being such a simple one. We, Feed Microscopists must, if we so choose, not only quantify but also recognize, correctly identify and name the ingredients (analytes) found as per preset definitions agreed upon by Feed Control Officials. Therefore, prompts for specific analytes as used by our colleagues in other LPPs would have, needless to say, defeated the purpose. Our reporting system had to be designed in a whole new manner. The reporting system was set up such that participants could enter the ingredient and percent quantity. But, to aid in the processing of the entries, a list of 300 of the more common and identifiable ingredients was compiled from the over 8000 ingredients listed in the AAFCO official publications (2005) and Canadian Feed Regulations, such that participants could enter the number assigned to the ingredient. Naturally there were a few additional fields to allow the entry of names that were not on the list for, as they may happen, the less common, the "brand-new-rarely-been-seen-before", the "should-not-even-be-there" and the "what-were-they-thinking-of" ingredients or adulterants. After all, feeds are a recycling industry. Although the reporting system still needs to be fine tuned to eliminate the need for lining up and rearranging entries to generate a presentable report, it is still a good start.
As for the LPP itself. Participants were again presented with 6 samples. Sample 1 - Pig Starter Supplement, 2 - Laying Chicken Complete Feed, 3 - Beef Feed, 4 - Calf Starter Feed, 5 - Dairy Concentrate, and finally sample # 6, the infamous Laboratory mix where no one cares about nutritional value or balanced nutrient levels and all things are possible. Twelve to sixteen responses were received for each sample. A more detailed report was presented to the participants.
Among the challenges faced by the feed microscopist, one must learn the definitions and processing of the ingredients to distinguish subtle differences between ingredients of the same origin processed in different manners. For example, in the 3rd sample, there were two ingredients of corn origin with very similar appearance, Corn Gluten Feed and Corn Distillers Grains. In corn gluten feed, the germs are dull as they are covered with gluten. Whereas, in Distillers grains, the germs are shiny and curled as they have been through fermentation and distillation process but may contain "solubles" that resemble gluten. In the first sample, only corn gluten feed had been added but some identified it as corn distiller's or a combination of both. In samples 4 and 5, participants found linseed meal and ground linseed receptively. As a rule of thumb, oil seed meals are the cake resulting from the removal of most of the oil by chemical or mechanical means. A quick squeeze between the tips of forceps is all one needs.
The proportions and morphology of markers (evidence) in related ingredients as well as adequacy of processing are also significant for accurate identification. For example, oat based ingredients were added to the 1st, 3rd and 4th samples. In the first, it was steamed rolled oat groats, oat groats are defined (1) as "cleaned oats with the hulls removed". Oat groats are easily misidentified as rolled oats as oat grains are not known to be strongly attached to their hulls but one would find more hulls had the latter been used as an ingredient. Alternately, the 3rd contained Oat Mill Feed which is defined as the by-product of oat groat industry therefore composed primarily of Oat Hulls but few oat grains. The fourth sample contained both oat groats and rolled oats, however, the "rolling" process had lead to very little hull breakage such that one could mistake this latter ingredient for the whole grain variety. Another example is soybean based products. When in meal or ground as in # 4 and 5, soybean hulls are thick and coated with "flesh" but when processed alone as in #1 (soybean hulls), they are often flat and paper thin. When dehulled soybean meal is added, as in #2, less pieces of hulls should be found but those found should be fleshy. Alternately, soybean feed, added to the lab mix ("the product remaining after the removal of ... from dehulled soybean flakes") appeared like rolled or pressed soybean and has no hulls.
The feed microscopist must also be able to discriminate between actual ingredients (or adulterant) and adventitious contaminants. The second sample, unbeknownst to participant, bore the warning "Do not feed to ruminants". Most participants did identify meat and bone meal (MBM, yeah microscopy!) but there was substantial variation in terms of the species of origin stated. Although the species of origin was not specified, one could deduce that this feed contained prohibited (bovine) meat and bone meal because of the warning. This was confirmed by short, relatively thin hair fragments with narrow medula and spotted pigmentation. Porcine MBM, as suggested by the presence of flattened bristles, was also likely present. One participant listed ovine MBM. Ovine would be supported by undyed wool fragments about half to a third the diameter of bovine hair with serrated cuticle margins and lack of medula. One must be cautious, however, as wool or cotton fibres could come from clothing (adventitious contaminant). In the 3rd sample, in addition to blood meal, the ingredient of animal origin was feather and not poultry meal. Processed feathers appear hydrolysed or melted with some but little barbules remaining intact. Feather meal could contain some muscle fragments as unavoidable in good manufacturing practices but less then would Poultry meal. In the case of sample 4, presence of cotton seed hulls was demonstrated by both the hulls and fibre but little cottonseed meal.
To aid in his or her quest to differentiate and identify all that can be identified, the feed microscopist can also resort to various spot tests as detailed in the Manual (2). For example, blood meal, as added to samples 1 and 3, can be identified using the tetramethylbenzidine (TMB) test. The TMB test can be converted to a "screening test" by sprinkling the light fines (from the floatation) onto a filter papers and moistening with the TMB solution. Green spots will appear if blood meal is present but the test should be confirmed on a slide to also observe the formation of air bubbles. Another example, as in the first sample, is dried whey vs milk. Dried whey can be detected through the presence of birefringent lactose crystals in the sample but powdered milk can also show the same crystals. However, milk powder will form little clouds when sprinkled on a drop of water (or dilute iodine to differentiate from starch).
Again, low tech does not mean simple.
This year's program was scored as in previous years, 1 point for every ingredient listed and stated on formulation and 0.5 point for ingredients judged to be equivalent. The top three cumulative scores were obtained by:
1. Mike Bucker, Division of Consolidated Laboratories of Virginia, Richmond VA USA 2. Neil Vary, Ottawa Laboratory (Carling), Canadian Food Inspection Agency, Ottawa, Canada and 3. Gary Ideus, ADM Alliance Nutrition, Quincy IL USA
However, this program is not a competition but really a learning tool and a means to confirm and maintain competence. Therefore, some new and rare ingredients were introduced in the Lab mix for participants learning pleasure and entertainment. The "brand-new-starting-to-creep-up-here-and-there" ingredient, courtesy of the Northern Crop Institute, was Cacao Waste Product which was identified by one participant as "Solvent Extracted Cacaomeal". This ingredient is not listed in either the AAFCO 2005 Official Publication or allowed by the Canadian Feed Regulations hence was not on the list, but, we all know, non-allowed ingredients are always a possibility and we must always be alert. The other rare ingredient was ovine (sheep) meat and bone meal. I have been told it has not been produced in Canada and the US for quite a number of years and was imported from New Zealand. It can be differentiated from other mammalian MBM by the presence of wool fragments as discussed above. Hopefully every one learned something new.
Finally, in a plea to our industry members and to further illustrate the difficulty of finding suitable samples for this program, we were unable to obtain the exact formulation for the fourth sample although it had been promised, thus preventing those who estimate ingredient proportions to evaluate the precision of their estimation. To those of you who have good samples or rare ingredients to share, please do so.
On that note I announce my resignation as provider/coordinator of this program. It has been a valuable learning, growth promoting and challenging experience. I wish to thank all those who have helped over the years by providing samples and secret recipes without which this program would not exist and I turn this over, and back, to Gary Ideus who graciously accepted to be volunteered for this honour.
Kindest regards and have a wonderful summer
1 Unless otherwise cited, definitions are as per American Feed Control Officials Official (AAFCO) Publication 2005.
2 Manual refers to: Manual of Microscopic Analysis of Feedstuffs, American Association of Feed Microscopists, 1992, available through AOCS Publications.