“STRATEGIES EXIST FOR COPING WITH POOR QUALITY GRAIN: PART 2”
As discussed in the previous issue of Milwhite’s Journal, it is best to have a minimal amount of quality deterioration throughout the entire period that any grain is in storage at the feedmill prior to being incorporated into diets of poultry and other animals. This can only be accomplished through good grain storage management practices. The moisture content of grain, especially corn, is the major factor that usually determines the rate of deterioration due to mold and bacterial contamination. Whenever the moisture content of grain approaches 14% or more it cannot usually be stored for extended periods of time without an advanced rate of quality deterioration. In this second of three consecutive issues of Milwhite’s Journal successful strategies are presented that are known to decrease the rate of quality deterioration of stored grain.
STRATEGIES FOR STORING GOOD AND POOR QUALITY GRAIN
When grain arrives at a feedmill, the manager and quality control personnel must be able to quickly categorize whether the grain is good quality or poor quality and have clean silos prepared to receive the grain. This distinction in grain quality must be made immediately upon arrival of the grain and must be made based on a company’s preestablished quality control standards. It would be best to screen all incoming feedstuffs for the presence of mycotoxins and the decision to accept or reject based on their toxin levels. After the distinction is made a company is then in a better position to implement standard handling procedures for each quality category into which a grain is placed. Rotation of stock grain inventory, following the first in-first out rule, is also another very important practice to help assure that grain quality will be maintained during storage. New grain should never be placed in a silo on top of old grain. In the case of good quality grain, the number one goal of the company should be to maintain the grain quality as high as possible throughout storage. On the other hand, if the quality of grain is determined to be poor then the company must be in a defensive position. This means that the company must do everything possible to “minimize the damage” that this grain will have on bird health and performance.
GOOD QUALITY GRAIN-MAINTAINING IT’S QUALITY DURING STORAGE
From the standpoint of how to minimize problems associated with mycotoxins, the first step to take upon arrival at the storage area is to subject the grain to cleaning. Cleaning will eliminate a lot of foreign material as well as fine particles (dust). It is an established fact that fine and cracked grain particles will have the greatest concentration of mycotoxins when compared with the concentration associated with intact grain. Intact grain kernels will usually not have any detectable or high concentrations of mycotoxins because the endosperm starch has not been exposed. A majority of the foreign material that is commonly associated with grain will facilitate mold growth since it usually has a high spore load and/or moisture content. Cleaning can be accomplished with high speed fans that remove and collect dust, cracked grain and other lighter density moldy material. Many companies do not clean grain upon its arrival at the feedmill because of the associated weight loss, time involved and cost. However, in many cases, the lack of grain cleaning will usually prove to be more costly in bird performance because of the mycotoxins that will be consumed and the nutrient diluting effect that foreign material will have in the final diet.
Once grain is cleaned it should be dried to an acceptable moisture content. Usually this moisture level is approximately 12 or 13% in order to decrease growth of mold, yeasts and bacteria. Drying also helps to prevent grain from having a tendency to “pack” or “cake” during storage. Controlling the amount of heat during drying is essential in order to prevent condensation upon cooling and kernel cracking that will lead to mold invasion during storage. Some moisture in grain is necessary, however, in order to prevent excess dryness, which leads to excessive grain cracking and dust formation during handling and grinding. Excess moisture is considered to be the greatest enemy of stored grain because it will promote growth of mold and other microbes. When microbes grow heat is released and an increase in the temperature of stored grain is a good indicator of moisture and mold invasion. If excess moisture is present in the grain at the time it is stored it will contribute to a more rapid deterioration of grain quality, increased insect activity and “hot spot” formation. Moisture leakage into silos must be prevented at all costs and this means that silos must continually be inspected for possible moisture entrance points. Even though stored grain often contains an ideal uniform moisture concentration, this should not lead to a false sense of security since moisture is always a threat to grain quality. It should also be remembered that water is a by-product of mold growth along with CO2 and heat. This source of water is often not realized until “hot spots” caused by mold are detected in stored grain.
STORAGE SILO MICROCLIMATE
Even though stored grain will often contain an ideal uniform moisture concentration, this should not lead to a false sense of security. A microclimate exists within storage silos and because of this the grain is constantly exposed to changes that are occurring. The constant solar heating during the day and cooling at night can lead to problems. Over several months of storage the grain moisture will have a tendency to migrate within the silo. This is caused by convection currents that arise during the hot days and cool nights allowing the moisture in hot grain to move upward and toward the cooler areas where condensation accumulates near the interior periphery of the silo. The moisture accumulation in these specific areas can reach 16 to 17% and will result in mold growth leading to buildup of caked moldy feed on the inside of the silo walls.
One of the best ways to minimize moisture migration is to dissipate solar heat accumulation near silo walls by moving air within the silo in order to maintain a more uniform temperature which diminishes condensation. Aeration is best when the outside temperature is equal to the mean inside silo temperature. Normally, aeration moves air within a silo at a velocity of about 0.1 CFM/bushel of grain. Higher air velocities may result in excessive grain drying. In certain situations where aeration is not possible for one reason or another, anti-caking agents are used once the grain has been cleaned and dried. The protective effects of anti-caking agents will indirectly result in the minimization of mycotoxin production by helping to deplete from the microenvironment inside the silo one of the five requirements for mold growth– “moisture”. The ideal anti-caking agent should be inert and adsorb only water and not interfere with dietary nutrient utilization and efficiency of medications or other agents added to promote animal performance and health. Also, it is common in hot tropical areas to use commercially available organic acids, such as propionic and others in stored grain in order to prevent mold growth. In the next issue of Milwhite’s Journal information will be presented that will identify ways of minimizing the damage that occurs to animal performance and health as a result of having to use poor quality grain in diet formulation.
The information in this issue of Milwhite’s Journal was compiled by Dr. Orlando Osuna, Director of Health Services at Milwhite, Inc. and Dr. Richard Miles, Professor Emeritus, Univ. of Florida, Gainesville, FL, USA.