Rancidity Fats and oils present in the ground materials are primarily re- sponsible for the development of rancidity. Oxidation of fats and oils (rancidity) is a natural reaction that occurs between unsaturated fatty acids and free oxygen. In this reaction, a peroxy radical is formed when the triglyceride free radical re- acts with an oxygen molecule. The peroxy radical then reacts with another triglyceride, forming very unstable hydroperox- ides, and breaks down to some secondary products such as aldehydes and alcohols, which contribute to the unpleasant flavours associated with rancid fats. These may also form oth- er polymers that are unavailable and therefore lower the en- ergy content of the fat and they are capable of destroying the fat-soluble vitamins contained in feeds (vitamin A, D, and E) and also cause the loss of carotenoid and xanthophyll pig- ments. The rancid feed may also lead to digestive upsets and thus reduced performance of chickens (Table 3). Antioxidants, therefore, should be added to the product as soon after preparation as possible. Compounds such as eth- oxyquin (1,2-dihydro-6-ethoxy-2,2,4- trimethyl quinoline), BHA (butylated hydroxyanisole), and BHT (butylated hydroxy- toluene) are extremely effective antioxidants and can be used both efficiently and economically. Combinations of these an- tioxidants are normally found in commercially available


products to take advantage of the different properties of each compound.


Ground versus unground feeds Ground feeds will tolerate up to about 11% moisture under average conditions without mould forming during storage. Moisture levels in ground feed higher than the above will probably result in heating, caking, and/or mould during


Table 2: Moisture levels of feedstuffs for safe storage


Moisture percent for safe storage


Feedstuff Wheat Maize Barley Oats


Soybean


Linseed cake Fishmeal


Meat and bone meal Source: T. W. Perry (1982)


(3 months) 15.7 14.8 14.8 14.5 13.3 12.3 11.5 10.3


(2-3 years) 14.6 13.7 13.6 13.4 11.0 11.1 9.9 8.7


▶ ALL ABOUT FEED | Volume 29, No. 4, 2021


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