Effect of Molded Rice on Growth of Young Chicks

Abstract

Two samples of rice artificially molded with Aspergillus flavus and Aspergillus parasiticus and pure aflatoxin B1 were fed to total 386 one-week-old male White Leghorn chicks for 12 days to compare the effect of molded rice on the growth of the chicks with that of pure aflatoxin B1.Body weight gain and feed intake of the chicks decreased in inverse proportion to the dietary level of molded rice and pure aflatoxin B1. Since feed efficiency, i.e. growth rate on unit feed intake, also decreased in inverse proportion to the dietary level of the samples, it was certain that the depression of growth was not simply due to the decrease of feed intake.On the working hypothesis that the response of chicks to molded rice is simply and only correlated with the content of aflatoxin B1 in molded rice, analyses of regression and covariance were carried out on the growth response of chicks and dietary aflatoxin B1 level. No difference was observed statistically between two regression lines corresponding to Samples 1 and 2, respectively, so that these two lines were amalgamated into one line. The amalgamated line was found different significantly from the regression line on pure aflatoxin B1. The findings were true with body weight gain, feed intake and feed efficiency, and were agreeable with those reported previously with laying Japanese quail.From the ratio between two regression coefficients, one for pure aflatoxin B1 and the other for molded rice, it was calculated that the growth retarding effect of aflatoxin B1 in molded rice was about four times stronger than that of pure aflatoxin B1 on iso-aflatoxin B1 level.Weight of the liver of the chicks fed either molded rice or pure aflatoxin B1 was similar, which was significantly heavier than that of the chicks fed the control diet. The findings suggest that the effect of molded rice to increase liver weight is in proportion to its aflatoxin B1 content.Considering the effects of molded rice on growth response and on the liver weight together, it was suspected that molded rice has an unidentified factor or factors other than aflatoxin B1, which has growth retarding effect about three times stronger than pure aflatoxin B1 has, but which has little effect on the liver weight.No residue of aflatoxin B1 in the liver of the chicks on the diets containing the highest level of molded rice and pure aflatoxin B1 was detected. The threshold sensitivity of the detection was 10ppb.