Assessing Adequacy of Processing
One of the critical observations by the authors is the evaluation of flakes or the manure from cattle fed the flakes. They remind us that starch content of the manure as an indication of starch digestion is the best way to evaluate the adequacy of processing. But the physical measurements are easier for most feedlots to perform. The physical quality control test for flakes are: (1) flake thickness, (2) flake density, (3) starch solubility, (4) and enzyme reactivity.

Flake Thickness
They state that: "One advantage of flake thickness as a measure of flake quality is that this measurement is independent of time, conditions, or location (i.e., at the holding bin, at the feed bunk, in a sample of complete mixed feed)."

Flake Density
Flake density (example lb/bu) as measured by most feedlots is variable. The authors warn us that using flake density varies with location of taking the sample, under the roll vs. from the holding bin, moisture loss, inconsistency of the person measuring and other factors.

The mill operator is checking flake density. His goal is 26 lb/bu directly below the roll or 28 lb/bu for fresh flakes as they enter the storage pile.

"Unfortunately flake density appears less reliable as an index of in vivo (real animal tests) starch digestion." They suggest that flake density "should be measured consistently, either within a few seconds after the grain is flaked or after the sample has been allowed to cool."

Fecal Starch Analysis Suggested
"Live animal measurements are the ideal indicator of the adequacy of the steam flaking process," stress the authors. They report a close relationship between starch in the manure and ruminal starch digestion and 91 percent of total tract starch digestion. Most feedlot operators may be hesitant to use this procedure for quality control at their facility. One of the problems is variation in the manure from animal to animal and contamination of the manure from soil or old manure. It seems that if this procedure is used, it should be performed by a trained feedlot employee or a third party and be part of the over all quality control evaluation of the flaking process.

Processing Mechanics
The authors remind us that there are five critical mechanical factors that influence the quality of stream flaked corn: (1) steam chest temperature, (2) steaming time, (3) roll corrugation, (4) roll gap, and (5) roll tension.

Steaming Time
"Very little research has evaluated the minimal steaming time necessary to produce an optimal flake," according to the research. Zinn (1999) demonstrated that steaming for more than 30 minutes did not enhance either starch digestibility or the NE value of corn flaked to a density of 0.31 kg/l (24 lb. per bushel). Steaming time is controlled by the size of the chamber and the speed of the feeder bar according to the authors. In my experience, the feeder bar, commonly called feeder roll or peg feeder, is often the problem point in good flaking procedures. The authors emphasize that uniform feeding of steamed grain to the rolls is very important for flake quality.

Roll Gap and Roll Tension
Over the years of watching operators of flaking mill adjust the equipment, I am convinced that the adjustments are more "art than science." The experienced operator sets the roll close and then adjusts the tension of the springs or the pressure of the hydraulics to achieve the flake that is their goal.

The authors of the review suggest there are two methods for adjusting the rolls. The first method is the zero tolerance method. The rolls are set together at the start, and then the pressure of the rams are adjusted as the grain begins to force the rolls apart. The second method is to set the rolls at a gap of 0.8 to 1 mm and then set the ram pressure springs or hydraulics at a high pressure. The researchers state this method will achieve a "more uniform and consistent flake." @copy;