EFFECTS OF DIETARY LIPID SOURCES ON TISSUE FATTY ACIDS PROFILE ANDGROWTH PERFORMANCE IN FEMALE RICE FIELD EEL MONOPTERUS ALBUS,ZUIEW

Abstract

In order to basically figure out the metabolism and demand on the fatty acids of rice field eel,Monopterus albus Zuiew,and provide a frame of reference on selective using different lipid sources for rice diets production of field eel,six isonitrogenous(44% crude protein) and isoenergetic(19.4 MJ/kg) experimental diets were formulated by using six different lipid sources:fish oil(FO),soybean oil(SO),and linseed oil(LO),ARA + peanut oil(APO),peanut oil(PO) and pork lard(PL).Female rice field eels(initial weight of 15.5 g) were fed with these diets for 10 weeks.The fats and fatty acid compositions in the muscle liver and ovary of these eels were analyzed by means of chloroform-methanol and gas chromatography(GC) and the growth performance were evaluated with the parameter of specific growth rate(SGR).The results showed that there were effects of different lipid sources on the growth performance of rice field eels.The SGR of rice field eels fed with PO without n-3 polyunsaturated fatty acids(PUFAs) was significantly lower than those fed with SO and FO(P0.05);the specific growth rate(SGR) of rice field eels fed with SO was significantly higher than those fed with LO,APO,PO and PL,except FO(P0.05).There were positive linear correlation between the content both 18:3n-3 and 18:2n-6 in the various tissues of rice field eels and those in experimental diets.When the experiment diets were lack of eicosapentaenoic acid(EPA,20:5n-3) and docosahexaenoic acid(DHA,22:6n-3),there were positive logarithmic correlation between the content of EPA,DHA in ovaries and the content of 18:3n-3 in diets;while the ex-perimental diets were lack of Arachidonic acid(ARA,20:4n-6),there were positive linear correlation between the con-tent of ARA in muscle,liver and ovary and the content of 18:2n-6 in diets.The content of EPA and DHA in the various tissues of the rice field eels fed with diet(FO) with EPA and DHA were significantly higher than those of the rice field eels fed diets(LO,SO,PL,PO) without EPA and DHA(P0.05).In general,the n-3PUFAs and appropriate n-6/n-3 ratio were important for the growth of rice field eels.Soybean oil,linseed oil and pork lard were feasible lipid resources for replace fish oil on growth of rice field eels and soybean oil is preferable lipid resources.The fatty acid(18:2n-6,18:3n-3,ARA,EPA and DHA) profiles of liver,muscle and ovary reflected profiles of the corresponding dietary lipid sources.The rice field eel only possess the infirmatory ability to synthesize EPA and DHA from linolenic acid(18:3n-3) and ARA from linoleic acid(18:2n-6) for the limitation in the capacity of fatty acid desaturation.