Ly et al., 2002. Livest. Res. Rural Dev., 14 (1): 1-6

Seven samples from six aquatic plant species available in the Ecological Farm of UTA, Chamcar Daung, Cambodia, were selected for a screening test to evaluate in vitro pepsin/pancreatin digestibility of N and to explore the possible relationships with other non conventional tests for assessing their nutritive value for pigs. The samples were the aerial part of water hyacinth (Eichhornia crassipes) and water spinach (Ipomoea aquatica), and the entire plants from water lettuce (Pistia stratiotes), azolla (Azolla pinnata), duckweed (Lemna minor) and spirodella (Spirodella polyrhyza). The duckweed was analysed fresh or after sun-drying. Dry matter (DM) values were from 6.3 to 91.1%; nitrogen (N) and neutral detergent fibre (NDF) concentrations (dry basis) were from  2.31 to 5.54% and 29.7 to 58.1%, respectively. Water solubility of N and in vitro digestibility of N were high and within a relatively narrow range (N solubility, 59.3 to 81.5%; in vitro, pepsin/pancreatin N digestibility, 50.5 to 76.6%). In vitro N digestibility was positively associated with water soluble N (r=0.74), water soluble DM (r =0.71) and in vitro DM digestibility (r=0.75) but not with NDF-linked N (r = -0.043). In vitro N digestibility was highest for azolla and fresh duckweed (76.6 and 75.4% respectively) and lowest for water hyacinth (50.5%). Water soluble DM (r = 0.74) was a better predictor of in vitro DM digestibility than NDF (r = -0.48). The results of this study show that water soluble N is a useful indicator of the digestibility for pigs of the protein in water plants