Detritus of plant origin as a food source for Penaeus indicua H. Milne Edwards

Abstract

The objective of the present study was to evaluate the feasibility of using plant detritus as an exclusive food source for the juvenile of Penaeus indicus and also to find out the level of its in corporation in a standard diet for the prawn in place of animal protein sources. When four plant detritus were simultaneously presented to p.indicus juvenile of size 25-32 mm and 110-150 mg, they exhibited best preference for detritus from Rhizophora apiculata, followed by chromolaena odorta, Pistia stratiotes and paddy detritus. Two better preferred plant detritus sources viz. R.apiculata and C.odorata, were subjected to bulk digestion and the improvement in protein level by way of microbial growth during the process of decay was recorded. Since C.odorata showed a better protein level (Max.av.25.716%) on the fifteenth day than R.apiculata (Max.av.7.528%) on the twentieth day, C.odorata detritus was used for the next two feeding experiments: the first to find whether it could be used as exclusive protein source and the second to find the level at which this could be used to replace animal protein source in a standard diet for P.indicus. The first feeding experiment, for a period of 28 days, to evaluate the feasibility of using plant detritus as sole protein source revealed that an exclusively detritus based diet is not suitable for P.indicus juveniles. The detritus based diet produced lower survival, growth, protein sufficiency ratio, protein digestability and high food conservation ratio when compared to that of control diet prepared with clam meal. The second experiment done with eight diets for a period of 21 days revealed that plant detritus could be used for substituting upto a level of 50% of the animal protein source in a standard prawn diet, without producing any adverse effect on growth and survival. While, a diet containing 10% plant detritus fared even better than a diet which was totally devoid of detrital protein. The growth, food conversation ratio, protein efficiency, apparent digestibility and protein digestibility values obtained for various diets did not vary significantly upto a stage where 50% of the animal protein was substituted with detrital protein, beyond which the values declined. The best values were obtained for the diet FD2 and the lowest for the diet FD8.