Better Farming Series 44 - Processing of Cassava and Sweet Potatoes for Animal Feeding (FAO, 1995, 49 p.) About the cassava plant (introduction...) What root yields can you get? Feed value of cassava roots The problem of cyanide in cassava

Better Farming Series 44 - Processing of Cassava and Sweet Potatoes for Animal Feeding (FAO, 1995, 49 p.)

About the cassava plant

15. In different countries, cassava is known by different names. In your country, it may be known by one of the following names: yuca, manioc, tapioca or mandioca.

16. Cassava is an important crop in warm climates because:

- it can adapt to many conditions;
- it can grow in areas with little rain;
- it can grow and produce in poor soil;
- it is hardy and easy to grow;
- it is free from serious insect pests and diseases.

That is why cassava is a popular crop in most tropical countries.

17. The number of swollen roots in a plant and their size vary greatly among different cultivars of cassava. You usually get between five and ten roots in a plant.

Leave

18. Once the roots have matured, you can harvest them at any time. If you do not need the roots immediately, leave them with the plant.

Cassava plant

19. This is a big advantage of cassava. You can leave the roots underground even after they mature. This is called underground storage of cassava roots.

20. Different cultivars of cassava mature at different rates. But we can group them into two types.

Short- season cultivars have roots that are ready for harvest in six to nine months after planting. They produce sweet roots.

Short- season cultivars

Long- season cultivars have roots that are ready for harvest in 12 to 15 months. They produce bitter roots.

Long- season cultivars

What root yields can you get?

21. Cassava root yields vary widely in different regions:

- In Africa, Central America and the Caribbean, the average yield is 6 400 kg of roots from a hectare.

- In Asia and South America, the average yield is 11 600 kg per hectare.

22. You can get much higher yields. A good farmer using recommended cultivars and cultivation practices can expect up to 40 000 kg per hectare.

23. If you are getting low root yields, talk to your extension worker. Find out how you can increase yields.

Extension worker

Feed value of cassava roots

24. Cassava root is a carbohydrate food. It contains a lot of carbohydrates in its dry matter. There are more carbohydrates in cassava roots than in cereals and other tubers.

Cassava root is a carbohydrate food

25. The amounts of carbohydrates contained in 1 kg dry matter of different foods are given below.

Cassava roots	920 g
Sweet potato tubers	890 g
Yams	860 g
Rice	840 g
Maize	830 g
Sorghum	810 g
Millet	800 g

26. You know that cassava root is starchy. The carbohydrates in cassava root are made mainly of starch. Cassava starch is highly digestible for all animals.

27. Dried cassava roots contain a similar amount of energy to cereal grains. So you can use cassava roots instead of cereal grains in animal feeding.

28. Cassava roots do not have much protein. Protein is necessary for the building up of body muscles and for animals to grow.

29. The amounts of protein that you can get from 1 kg of dried cassava roots and some other energy feeds are given below.

Cassava roots	25 g
Sweet potato tubers	45 g
Yams	80 g
Rice	60 g
Maize	90 g
Sorghum	100 g

30. This means that you cannot use cassava roots as the sole feed. You must always use them with feeds that will supply enough protein.

You cannot use cassava roots as the sole feed

31. Cassava root is not a good source of minerals and vitamins. It contains low amounts of minerals and vitamins.

32. Minerals and vitamins are necessary to keep animals healthy.

33. This means that when you are using a lot of cassava to feed the animals, you must combine it with feeds that are rich in vitamins and minerals.

34. This is true for most feed materials. Whatever the feed material you may be using, you must always combine it with other feeds to get a balance of minerals and vitamins.

Combine feed

35. You can purchase the vitamins and minerals from your dealer in the form of supplements:

- Shell grit supplies calcium.
- Bone meal and dicalcium phosphate supply calcium and phosphorus.
- Vitamins and other minerals are available in small packets as premixes.

Bone meal, vitamins and other

36. Cheaper feeds, such as leaves, can also be used to supply vitamins and minerals

Cheaper feeds

The problem of cyanide in cassava

37. Fresh cassava roots contain a poisonous substance called hydrocyanic acid. It is also known as prussic acid. If fresh cassava roots are eaten, this poison can make people, as well as animals, very sick.

Animal

38. Some people do not like to use cassava roots because they have this poison.

39. Fortunately, there are simple ways of reducing this poison. You should know that:

- there are cassava cultivars with low levels of cyanide;
- the outer peel of the roots has more cyanide than the flesh;
- cyanide levels can be lowered by proper preparation of the roots;
- the bad effects of this poison can be overcome by feeding protein feeds along with the cassava.

Some cultivars have low cyanide levels

40. Some cultivars have low levels of cyanide and do not cause any problems. These cultivars usually produce sweet roots.

41. Some cultivars contain high levels of cyanide. They can be poisonous. These cultivars usually produce bitter roots.

42. If you know whether the cultivar that you are growing is bitter or sweet, you can get an idea of the cyanide level in its fresh roots and take precautions.

Outer peel has more cyanide.

43. The outer peel of the cassava root has ten times more cyanide than the inner flesh.

44. You know that the peel can be loosened and easily removed from the flesh. Removing the peel makes roots less harmful.

Peel

Processing can reduce cyanide levels

45. If cassava has this poison, you may ask how it can be used as a feed.

46. Cyanide in cassava roots is not a problem if you:

- process the roots properly;

- feed the roots together with other feeds which help the body to overcome the bad effects of cyanide.

47. How can you reduce the cyanide levels? You can remove part of the cyanide by drying, heating or boiling the roots.

Cianide

48. Some of the cyanide can also be leached out by soaking the roots overnight in water.

49 When you cut or grate the roots, a good part of the cyanide is released.

50. You can also reduce cyanide levels by fermentation.

51. You can see that there are many ways of reducing the cyanide in cassava roots:

- cutting or grating;
- soaking in water;
- boiling or roasting;
- drying;
- fermentation.

52. Combinations of these methods are more effective in reducing the cyanide.

Protein feeds must be given

53. Good protein feeds are necessary when you are eating or feeding cassava roots.

54. You must eat good protein foods such as pulses, meat. eggs or fish.

Pulses, meat. eggs or fish

55. When enough protein is eaten, the body changes cyanide into a less harmful substance.