Influence of Insoluble Dietary Cellulose on Digestive Enzyme Activity, Feed Digestibility and Survival in the Red Claw Crayfish, Cherax quadricarinatus (von Martens)

Red claw (Cherax quadricarinatus) is a freshwater crayish species with recognized potential for aquaculture. To better understand the digestive processes and nutritional requirements of red claw, we have examined the effects of dietary cellulose on (1) digestive enzyme activity and diet digestibility and (2) survival rate, feed conversion ratio and growth performance. In the first study, a reference diet (RF) and test diets consisting of 70% RF and 30% a-cellulose or Fuller’s earth were prepared. Analysis of digestive enzyme profiles revealed that amylase and cellulase activities in midgut gland (MG) extracts were highest in the red claw fed on a diet containing 30% Fuller's earth and lowest in those fed on a diet containing 30% a-cellulose. Supplementation of the RF diet with either 30% a-cellulose or Fuller’s earth signi¢cantly reduced apparent dry matter ADMD) and apparent protein digestibilities (APD). In the second study, a feeding trial was conducted using diets supplemented with different levels of a-cellulose. A major finding was that dietary cellulose levels above 12% were correlated with signifcant reductions in survival rate, specific growth rate and feeding efficiency. Based on these findings,we suggest that although cellulase enzymes are present in the red claw digestive system there are no apparent nutritive benefits obtained by including insoluble cellulose in diets for this species

The comparative evaluation of the nutrient composition and sensory attributes of four vegetables cooked by different methods

Summary The following four vegetables; beans (Phaseolus vulgaris var. vulgaris), brinjal (Solanum melongena var. esculentum), knol-khol (Brassica oleracea var. caulorapa) and radish (Raphanus raphanistrum satvius) were processed either by conventional, pressure or microwave cooking methods and were analysed for their nutritional and sensory profile. Raw samples were used as controls. Microwave cooking resulted in greater moisture loss when compared with vegetables cooked by other methods. The protein, fat, total ash, calcium, phosphorus, iron, and dietary fibre contents of the vegetables did not differ significantly in raw or cooked vegetables. Ascorbic acid was destroyed to the greatest extent by pressure cooking followed by microwave and conventional method. The sensory attributes of cooked vegetables, as evaluated by a paired preference test, revealed that there were no significant differences between cooked radish and knol-khol but, in the case of beans and brinjal, microwave and conventionally cooked samples were preferred over pressure cooked ones