CHEMICAL AND ENERGETIC CONTENT OF CORN BEFORE AND AFTER PRE-CLEANING

Abstract

The poultry industry normally has little control over the raw material that arrives at the processing plant. This experiment aimed to evaluate chemical and energetic quality of corn obtained in a feed mill before and after pre-cleaning. Twenty samples of 30 kg of corn each were taken from trucks delivering corn to the mill. The trucks were then unloaded and the material passed through a pre-cleaning process when another sample was taken. Samples were graded and physical properties evaluated: density (g/L), grain percentages of foreign material, impurities, fragments, broken, soft, insect damaged, fire-burnt, fermented, damaged, cracked and fine particles, as well as chemical composition analysis: Apparent metabolizable energy for poultry (AME), ether extract (EE), crude fiber (CF), starch (STA), water activity (WA), crude protein (CP), digestible and total lysine, methionine, cystine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine, histidine and arginine. The experiment was a randomized design with two treatments (before and after pre-cleaning) and twenty replications. Data was analyzed using SAS ® and treatment differences obtained using F test. Correlations and principal components were calculated. There was a decrease in density after the pre-cleaning process, which was probably due to the removal of earth and stones rather than grain and its fractions. Significant increases were found for insect damage, fermented and damaged grain while fire-burn was significantly reduced after the pre-cleaning process. Starch increased after pre-cleaning which is a result of contaminants that normally are poor in this carbohydrate, but fiber levels increased too. Apparent metabolizable energy, aminoacids, digestible (P<0.05) and total (P<0.05) histidine, total lysine and methionine (P<0.1) levels were reduced after pre-cleaning. Density was higher when there were fewer impurities such as straw, husk or small grains. Broken corn was positively correlated (P<0.05) with foreign material (0.63) and fragments (0.76), while proportion of damaged corn was positively correlated with foreign material (0.68), fragments (0.58) and broken corn (0.83). In this study, even in samples classified as excellent quality before pre-cleaning, the pre-cleaning process was effective in reducing humidity and water activity which helps control the growth of fungi or other microorganisms. Starch and fiber levels increased after pre-cleaning while apparent metabolizable energy levels was not improved by pre-cleaning.