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202. In most countries sweet potato tubers are used mainly as a human food. Only small amounts are used for animal feeding.
203. In Indonesia, the Philippines, Thailand, Papua New Guinea and Pacific Islands, about 10 to 15 percent of sweet potato production is used to feed animals, especially pigs.
204. In Japan and Malaysia, 20 to 30 percent of sweet potato production is used as an animal feed.
205. In China, most farmers use sweet potatoes for animal feeding. Chinese farmers know that sweet potatoes are a good feed.
206. Chinese farmers consider the whole sweet potato plant as a valuable animal feed. Both the tuber and the vine are used; nothing is wasted.
207. Sweet potato tubers are energy feeds. The amounts of energy that animals can get from 1 kg of sweet potato tubers and 1 kg of cassava roots are equal.
208. But sweet potatoes are better protein feeds than cassava roots.
209. On average, sweet potato tubers have 3.5 to 5 percent protein content. A kilogram of dried tubers will give 35 to 50 9 of protein. From Paragraph No. 50, you can see that this protein value is intermediate to the values of cassava and maize.
210. You have learned that cassava roots are low in minerals. Sweet potato tubers also do not have a high mineral content.
211. Sweet potatoes are, however, a better source of several vitamins, especially those tubers that have yellow or orange flesh.
212. Unlike cassava roots, sweet potatoes do not contain any poisonous substances.
213. But sweet potato tubers must not be fed uncooked because they contain a substance that can affect animals digestion of protein. This substance is called trypsin inhibitor.
214. When a feed contains trypsin inhibitor, protein will not be well digested and animals will grow slowly.
215. The level of inhibitor in tubers varies depending on the cultivar type. Most cultivars will not cause any problems.
216. Some cultivars, however, have high levels of inhibitor. If you feed uncooked tubers from these cultivars, animals will not grow well.
217. You should not get overconcerned about this substance in sweet potato tubers. You use many other foods every day that contain far more trypsin inhibitor than sweet potatoes do.
218. Beans, cowpea, green gram, soybean and other legumes have very high levels of trypsin inhibitor. But we still use them every day in our diets. How?
219. We cook or boil them before eating. Cooking and boiling completely destroy this substance. Once cooked, there are no problems.
220. Similarly, you can process sweet potato tubers into safe feeds by boiling or baking them.
221. Harvesting sweet potato tubers is easy. To dig the tubers from the soil, you need only simple implements. You can use sticks, a spade or a hoe.
Harvesting sweet potato
222. The tubers must be dug carefully. The skin of tubers can be bruised or damaged easily.
223. Damaged tubers will lose weight and spoil quickly.
224. Often the whole tuber will not spoil. Only the damaged part will become infected with moulds. These moulds produce toxins.
225. These toxins can cause serious problems. You must avoid feeding infected and mouldy tubers to your animals.
226. The infected parts must be trimmed and thrown away before feeding.
227. Progressive harvesting of sweet potato tubers is practised in many countries.
228. Large tubers are harvested first without disturbing the smaller ones, which are left to enlarge and harvested later.
229. Ground storage of sweet potatoes has some problems. You should know them.
If sweet potato weevils or termites are present, the tubers can be affected.
If heavy rains occur, the tubers may start rotting.
230. Freshly harvested sweet potato tubers can be kept for a few days without any problems. After a few days, the quality of the tubers will drop.
231. For longer storage, freshly harvested tubers must be cured. Curing will reduce weight loss and spoilage.
232. Curing also helps in the healing of damaged areas.
233. Curing is most effective at high temperatures (28 to 30° C) and at high relative humidity (85 to 90 percent).
234. Fortunately these are the conditions that are commonly experienced in tropical areas. Curing is therefore easy in tropical climates.
235. Good ventilation during curing helps in the quick healing of damaged areas.
236. If ventilation is poor, tubers will not be cured. Instead they will start to rot.
237. Curing can be done in a well- ventilated shed or in the sun. Curing for four to six days is sufficient.
238. If good storage principles are followed, cured tubers can be kept for three to four months.
239. Different methods of storage are used in different countries.
In the Philippines and Trinidad, cured tubers are stored in pits covered with dry sand.
In Barbados, mounds (or clamps) of dry sand are used.
240. Other storage methods include
- stacking in sheds;
- stacking on raised platforms;
-
storing in heaps on the floor;
- storing in baskets;
- storing in roof
spaces.
241. There is a big problem in the storage of sweet potatoes. That is sweet potato weevil. This pest can also attack the tuber while it is in the field before harvesting.
242. The weevils multiply quickly and riddle and destroy the tubers.
Weevil
243. If you are living in an area where weevil is a problem, you
must take precautions to control the pest.
244. You can practice:
- crop rotation;
- the use of cultivars that are resistant to
weevils;
- the use of
insecticide.
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