Utilization of ensiled sweet potato (Ipomoea batatas (L.) Lam.) leaves as a protein supplement in diets for growing pigs.

Four diets were formulated with protein from fishmeal (FM), groundnut cake (GC), ensiled sweet potato (Ipomoea batatas L. (Lam.)) leaves (SP) or ensiled sweet potato leaves with lysine (SPL). In experiment 1, 24 crossbred (Large White x Mong Cai) growing pigs were allocated randomly by sex into four groups of six pigs and given one of four diets. Experiment 2 was conducted using 16 crossbred pigs (Large White x Mong Cai) at four farms. On each farm, pigs were allocated to two experimental groups. One group was fed the FM diet and the other group the SPL diet. In experiment 1, the daily live weight gains (DLWG) were significantly higher (p < 0.05) for the FM and SPL treatments (542 and 536 g/day, respectively) than for the GC and SP treatments (464 and 482 g/day, respectively). Feed intake was highest (2.0 kg/day) for the SPL and lowest (1.7 kg/day) for the GC treatment (p < 0.05) and feed conversion ratio (FCR) was highest (3.8 kg/kg gain) for SP and lowest (3.5 kg/kg gain) for FM (p < 0.05). There were no significant differences for carcase measurements among diets (p > 0.05). The feed cost per kg live weight gain was lowest for the SP and SPL diets compared to the FM and GC diets. The results of experiment 2 show that there were no significant differences in feed intake, DLWG and FCR between the two diets (p > 0.05). In conclusion, sweet potato leaves can replace fishmeal and groundnut cake in traditional Vietnamese diets for growing pigs.