Effects of Oxidized Oil on Development of Encephalomalacia, Growth, Digestion and Organs in Chicks

Abstract

In order to investigate the relationship between the degree of fat oxidation and its toxicity, chicks were fed autoxidized soybean oil prepared by aeration at 60°C for various periods and the effects were studied. The autoxidation process of soybean oil consisted of 3 stages; inducing period, peroxide accumulation period, and carbonyl compound accumulation and polymer formation period. In the inducing Period, α-tochopherol content in the oil markedly decreased and peroxide accumulated very little. The tochopherol content in the plasma of the chicks fed this oil remarkably decreased, but only slight symptoms of encephalomalacia were found sporadically. In the peroxide accumulation period, β-, γ- and δ-tochopherol contents in the plasma were remarkably decreased, and the development of encephalomalacia increased with increasing peroxide value (maximum 83%), and most of the diseased chicks died. However, growth of the chicks and feed intake changed very little, also digestibility of the autoxidized oil did not differ from that of the fresh oil. In the carbonyl compound accumulation and polymer formation period, the accumulation of peroxide started to decline from the peak. Carbonyl compounds and free fatty acids accumulated considerably, and in the last of this period, viscosity of the oil increased extensively and large amounts of carbonyl compounds and free fatty acids were found. Although the development of encephalomalacia diminished in this period, body weight gain, feed intake, feed efficiency, digestibility of the oil and metabolizable energy reduced significantly and hypertrophy of the wall of small intestine. Judging from the above results, it seems that the development of encephalomalacia in chick is induced mainly by peroxide and it is undesirable to feed chicks on large amount of oil having peroxide value of more than 30. It is considered that the depression of growth and feed efficiency were caused mainly by carbonyl compounds etc. which are the secondary products of autoxidation of oil.