Three experiments were conducted at the Faculty of Agriculture, National University of Laos (NUOL), to study the effects of using taro leaf silage and water spinach as replacement for soybean meal in the diets of Mong Cai gilts during pregnancy and lactation.
The first experiment was on ensiling leaves of taro
(Colocasia esculenta (L.) Shott) with sugar cane
molasses, and was carried out at laboratory scale to determine the
optimum level of molasses for ensiling the leaves. After 7 days the colour for all treatments had
changed from green to yellow-brown and was darker at higher levels
of molasses. Each treatment had an acceptable smell. The pH values
for all treatments were around 6 at day 0 and then quickly fell
below 5, the value being dependent on ensiling time and the level
of molasses (P<0.05). At day 0 the concentration of NH3-N was
very low on all treatments, but from 7 days onwards the
concentration had increased with the time of ensiling on all
treatments; the highest value was 5,900 mg/kg DM on the 0% level of
molasses at 28 days. The ammonia-N concentration decreased as the
level of molasses increased. Ensiling for 28 days with 4% molasses
reduced oxalate concentration from 2.20 to 0.30% of DM. A level of
4% molasses and an ensiling period of between 14 and 21 days
appeared to be the most appropriate procedures for ensiling taro
leaves, as determined by pH, ammonia concentration and water
extractable DM and N.
The second experiment was to determine the effect of replacing soybean meal by a mixture of taro leaf silage and water spinach on reproduction and piglet performance in Mong Cai gilts. Fifteen Mong Cai gilts weighing 46±3.9 kg at service were used in a Randomized Complete Block Design (RCBD), with five replications of three treatments. Total dry matter (DM) intake decreased slightly with increased amounts of the mixture of taro leaf silage and water spinach. Live weights at farrowing and weaning declined as the amount of the mixture of taro leaf silage and water spinach increased. The feed conversion ratios (FCR) for treatments TW0, TW50 and TW100 were 3.09, 3.96 and 5.02 kg feed/kg gain, respectively. Live weight loss and percentage live weight loss in lactation were not affected by diet. The number of piglets born alive and at weaning did not differ among treatments (P>0.05). However, live weights of the litter at birth and weaning and weights of individual piglets declined as the foliages replaced soybean meal. Mortality to weaning ranged from 10.2 (TW0) to 7.5% (TW50) and was not affected by treatment. It is concluded that reproduction in the Mong Cai breed, measured as numbers of piglets born alive and weaned, and the interval from weaning to estrus was satisfactory when taro leaf silage and water spinach replaced soybean meal. However, total litter weights at weaning decreased, with a linear trend from 35.9 to 25.1 kg as the soybean was replaced by the forages.
The final experiment was on the effect of replacing soybean meal with a mixture of Taro (Colocasiaesculenta (L.) Schott) leaf silage and water spinach on apparent digestibility in Mong Cai gilts at two stages of gestation. Coefficients of apparent total tract digestibility (CATTD), measured by the acid-insoluble ash method, of dry matter, crude protein, organic matter and crude fibre decreased as the proportion of the mixture of taro leaf silage and water spinach that replaced soybean meal increased (P<0.001). There were no differences between the CATTD obtained in late compared with early gestation (P>0.05). It is concluded that digestibility of dry matter, crude protein, organic matter and crude fibre decreased with increased proportions of a mixture of taro leaf silage and water spinach replacing soybean meal in a basal diet of ensiled cassava root and broken rice. The limiting factor to the utilization of the taro leaf silage and water spinach appears to be the lower digestibility of the protein. There was no effect of stage of gestation on digestibility coefficients.