The June 2002 issue of the Journal of Animal Science included a invited review paper by Richard Zinn, Fred Owens and R. A. Ware. They discussed the importance in the flaking process of corn on starch digestibility and feed efficiency. They included in the paper a discussion of the effect of leaving the flakes in the pile or bin and letting the starch change from the continued heating and moisturizing in the pile. This process is referred to as retrogradation.

Retrogradation
They define retrogradation: "Retrogradation refers to the re-association of dispersed starch molecules." They explain that retrogradation causes a "glue like hardening of affected segments of starch, this decreases porosity of the internal starch matrix and limits rehydration and enzyme penetration." (I presume this means in the rumen and then down the small intestine and colon.) They report from lab tests, starch availability was 40 percent lower for the stored flakes than fresh flakes from the roller mill. Yet, with in vitro test,s the digestion was not different (in vitro is another lab test). I do not know of any feeding test of stored flakes versus fresh flakes. These results may be available.

Feeding Fresh Flakes
It appears from their paper, there is some risk of holding flakes in storage. So at this time we recommend that flakes be fed a soon as practical after flaking. Holding flakes overnight is probably not recommended at this time. Yet in many cases holding flakes is needed to "get the cattle fed." The retrograde process possibly is a slow process and a short time of holding flakes in a storage areas may be acceptable.

Drying Flakes
The authors state: "Allowing steam-flaked corn to dry is not synonymous with retrogradation." They report similar tests of starch gelatinization between fresh and dried flakes. They also report, "no differences were detected between fresh and air-dry steam flaked corn in ruminal or total tract starch digestion." It is interesting to remember that the original flaked research and demonstrations at Colorado State University by Matsushima and others were accomplished with dried flakes. Also dried flakes are routinely used for dairy cow feeding for material handling and mold prevention reasons.

Therefore, drying corn flakes for material handling reasons is recommended.

Keeping Flakes Intact
Most feedlots try to keep the flakes intact. The reason is prevention of fines. I do not know of research to absolutely determine if breaking up flakes really effects the starch utilization of the grain. My opinion is that making good flakes is a priority and good bunk management of getting the cattle to clean up the last feeding will overcome any problem of fines created by rough handling of flakes.

Questions or comments on this or any article by Dr. Jim Sprague can be addressed to him at 625 Grandview, Newton, Kansas, 67114. Or call him at (316) 283-8692.

Beef Producers Support Checkoff
According to the results of an independent survey released during the Cattle Industry Summer Conference, 66 percent of producers approve of the beef checkoff. Additionally, nearly 70 percent believe the checkoff helps producers compete with the aggressive promotion programs of poultry and pork, 71 percent believe that the beef checkoff program has value, even when the market is down and three out of five producers believe that if there were no beef checkoff program, no one else would pay for beef promotion. ©