Two experiments were conducted at the Centre for Livestock and Agriculture Development in Cambodia. The first was a study of digestibility and N-retention in crossbred pigs of diets with water spinach or water spinach mixed with mulberry leaves as protein sources in basal diets of cassava root meal plus rice bran, or sugar palm syrup plus broken rice. The second was study of growth performance of pigs fed water spinach or water spinach mixed with mulberry leaves, as protein sources in basal diets of cassava root meal plus rice bran or sugar palm syrup plus broken rice.
In Experiment 1 eight castrated male crossbred pigs (Large White X Local breed) of average live weight 25kg were used. The design was a 2*2 factorial within duplicated 4*4 Latin squares with 12 days per period, 7 days for adaptation and 5 days for faeces and urine collection. The aim of the study was to determine the digestibility and N retention of diets in which water spinach or water spinach mixed with mulberry leaves were used as protein sources in basal diets of cassava root meal (CR) plus rice bran (RB), or sugar palm syrup (SP) plus broken rice (BR).
In the factorial analysis there were no significant interactions between energy and protein (leaves) sources in any of the measured traits. There were no differences due to source of energy for dry matter (DM) and crude protein (CP) intakes (P>0.05), but crude fibre (CF) intake was higher on the CRRB diet, reflecting the presence of the rice bran, which had a higher crude fibre content than all the other ingredients. Coefficients of apparent digestibility of DM, CP and CF were higher for the SPBR diets. The source of protein had no effect on either feed intake or apparent digestibility coefficients (P>0.05). However, there were differences in N balance traits when 50% of the water spinach was replaced by mulberry leaves, with reduced N excretion in urine and higher N retention in absolute amounts and also in retained N as percentages of N intake and N digested. It is concluded that protein utilization efficiency is increased when the protein source is a mixture of water spinach and mulberry leaves rather than only water spinach.
In Experiment 2 sixteen female crossbred pigs (Large white X Local breed) of average live weight 20kg were allocated into 4 treatments in a 2*2 factorial arrangement with 4 replications. The factors were the energy source (cassava root meal plus rice bran or sugar palm syrup plus broken rice) and the protein source (water spinach or a 50:50 mixture of water spinach and mulberry leaves). The aim of the study was to determine the effect on growth performance of pigs of giving a mixture of mulberry leaves with water spinach compared with water spinach alone as supplements to energy sources with different levels of fibre derived from cassava root meal plus rice bran or sugar palm syrup plus broken rice.
Intakes of DM and crude protein were higher for CRRB compared with SPBR diets and were increased when mulberry leaves were mixed with the water spinach compared with water spinach as the only forage. Growth rates and feed conversion were numerically improved (P=0.22) when mulberry leaves were mixed with the water spinach compared with water spinach as the only forage.
It is suggested that the diuretic effect associated with water spinach could be responsible for the poorer growth performance when it is given at high levels (>28% in DM) in the diet.