Use of sweet potatoes (ipomoea batatas) forage as an animal feed

This study was conducted at Shambat Research Station during the period 2004/5-2005/6. Four varieties of sweet potato (Ipomoea batatas) were obtained from CIP and used in the study the varieties used were Tainumg No 6, Cemsa 744228, Maria Angola and Cemsa 78326. The main objective of the study was to investigate the potential of sweet potato forage as an animal feed compared with Abu Sabaeen (Abu 70) which is the most prominent roughage used for animal feeding in Sudan. In the first experiment the quantity of the tuber and forage produced by the four varieties of sweet potato was determined. The dry matter production of the vines from the four varieties of sweet potato varied between 1.32 to 4.12 tons haE-1and tuber production ranged between 11.2- 25.1 tons haE-1. There were no significant differences between the varieties in dry matter (DM), ash, crude protein (CP) and crude fiber (CF) content. In the present experiment the CP content as percent of dry matter for the four varieties of sweet potato vines were: 11.98, 10.25, 9.53 and 11.78% for the varieties Tainumg No 6, Cemsa 744228, Maria Angola and Cemsa 78.326, respectively. In the second experiment, an evaluation of the feed intake and digestibility of the forage of three of the four varieties of sweet potato was made and compared with Abu 70. Four sheep with weight and age ranging from 35-40 Kg and 12-16 months, respectively were allotted randomly to an experiment in a 4X4 Latin Square design. Feed was offered to sheep according to maintenance level. The chemical composition of the three varieties of sweet potato forage as compared with Abu 70 differed only in the CP content. Abu 70 showed the lowest value of CP content at 5.9 % compared with the highest value of 13.4% obtained for sweet potato forage from variety Tainumg No. 6 and the lowest value of 9.5% obtained from sweet potato variety Maria Angola while the value for variety Cemsa 744228 was 10.9%. The intake of DM in g/day or g/kg W0.75 by sheep of the three varieties of sweet potato forage and Abu 70 were not significantly different (P 0.05). The intake of DM in g/day from the three varieties of sweet potato forage and Abu 70 was 855.0, 968.6, 908.5 and 796.0 g/day, respectively. However the intake of DM in g/kg W0.75 from the three varieties of sweet potato forage and Abu 70 was 55.9, 64.8, 60.4 and 52.2, respectively. The digestibility of the forage from the three varieties of sweet potato and Abu 70 was 51.9 % for Tainumg No 6, 59.7 % for Cemsa 744228, 55.1% for Maria Angola and 49.5% for Abu 70. These differences were not significant. The third experiment was conducted to assess the feed intake of sweet potato vines and differences in weight gain of sheep fed on sweet potato forage compared with Abu 70. Growing rams with weight range of 14-24 Kg and age range of 6-7months were used. The rams were randomly divided into two groups each of 9 animals. Feed was offered to rams ad-libitum. The mean intake of DM of sweet potato vines was significantly higher than that of Abu 70 (P 0.001). The intake of DM of sweet potato forages in g/day, g/kg W0.75 and kg/l00 kg BW was 805.4, 82.9 and 3.9, respectively. On the other hand the intake of DM of Abu 70 in g/day, g/kg w0.75 and kg/l00kg BW was 582.7, 59.2 and 2.8, respectively. The results have shown that the group fed sweet potato forage was almost able to maintain their body weight during the experimental period (they lost a negligible weight of 0.02 Kg). On the other hand the group fed on Abu 70 has shown a considerable loss in weight amounting to 2.41 Kg for the same period. These differences were significant (P 0.01). Consequently sweet potato was practically providing the maintenance requirement of ram unlike Abu 70 where a marked loss in weight was recorded. At last evaluation of the profitability of sweet potato and Abu 70 was calculated when the two crops were fed to animals as maintenance ration while the production ration was made of a concentrate mixture. When Abu 70 was fed to sheep as farm produce the benefit cost ratio was 1.21 and when Abu 70 was purchased from the market the benefit cost ratio was 1.17.On other hand the benefit cost ratio when sweet potato forage was fed to sheep as farm produce was 1.56. In case sweet potato forage was purchased from the market the benefit cost ratio was 1.15. The higher profits obtained when sweet potatoes were produced on the farm and fed to sheep are attributed to the fact that the farmer is benefiting from both the tubers and the forage which is a by-product. The returns per cubic meter of water when the land was allotted to sweet potatoes were 1.71 SDG compared with 0.20 SDG in case of Abu 70. This shows that growing sweet potatoes may be more economical compared with Abu 70 both when considered in terms of pounds haE-1 or in terms of pounds/cubic meters of water