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Matching Livestock Systems with Available Resources |
MEKARN Regional Conference 2007 |
Two experiments were carried out to determine the effect of different nitrogen sources and harvesting time on forage biomass yield and chemical composition of sweet potato (Ipomoea batatas L.) and investigate the effect of replacing soybean meal with sweet potato meal on feed intake and performance of growing pigs on small hoder farms. An experiment was set out as a split-plot arrangement to evaluate the biomass of sweet potato during dry season in North Vietnam. The main plots were the sources of nitrogen, in a completely randomized block design with 3 farms, each farm as one block, replicated three times with three nitrogen sources (raw manure liquid [RML], biodigester effluent liqud [BEL] and urea liquid [UL]) at different harvesting time (60 days, 90 days, 120 days and 150 days of age).
Fresh vine (stem and leaf) and leaf biomass production at 30 day cutting intervals of RML treatment were 23.6 tonnes and 11.2 tonnes/ha, respectively, and higher than for the BEL treatment (20.6 tonnes and 9.9 tonns, respectively) and UL treatment (19.8 tonnes and 9.1 tonnes, respectively) (P<0.001), The DM, CP, CF, ADF and NDF contents of sweet potato vines (SWPV) were significant higher for the 60 days of harvesting time compared to the 90 days, 120 days and 150 days of age.
A feeding trial was conducted with 54 crossed pigs F1 (Large White x Mong Cai) at three farms with 3 dietary treatments and 3 replicate per treatment (2 pigs/replicate). The experimental design was a completely randomized block each farm as one block. Mean daily dry matter (DM), crude protein (CP) and metabolizable energy (ME) intakes were higher for the diet with replacing 50 % soybean meal with sweet potato leaf meal (SPLM50) (2.20 kg DM/day, 335 g/day and 26.6 MJ/day, respectively), and higher compared to the SPLM25 diet with replacing 25 % soybean meal with SPLM (2.08 kg DM/day, 317 g/day and 25.4 MJ/day, respectively) (P<0.05) and higher than for basal diet (BSD) without SPLM (2.06 kg DM/day, 311 g/day and 25.9 MJ/day, respectively).
Average daily weight gains (ADG) were significantly higher for SPLM25 diet (743 g/day) compared to the SPLM50 diet (658 g/day) (P<0.01). Feed conversion ratio (FCR) was significantly higher for the SPLM50 treatment (3.34 kg DM/kg BWG) compared to the SPLM25 and BSD treatments (2.80 kg and 2.94 kg DM/kg BWG, respectively).
It is concluded that soybean meal can be replaced 50 % with sweet potato leaf meal in the diets of growing pigs.