Cassava is one of the major crops in Vietnam, but the protein-rich foliage is an underutilized feed. This is the conclusion of Khuc Thi Hue in a dissertation from SLU. In smaller amounts, together with other feeds, cassava foliage proved to be an excellent feed for sheep, despite its content of hydrogen cyanide.
Cassava is a major staple food in many parts of the tropics. In Vietnam this crop is grown on around 500 000 hectares spread over almost the entire country. Based on this acreage, it is estimated that about 2.5 million tonnes (dry matter) of cassava foliage are produced each year as a by-product of root harvesting. The foliage is a protein-rich feed that can be used as feed for ruminants such as sheep, goats and cows. Today however, this resource is not fully exploited, partly because its content of cyanogenic glucosides can cause toxicity symptoms in animals when fed more than the tolerated dose. In her thesis Khuc Thi Hue shows how cassava foliage can be included in the diet of sheep without any negative impact on animal health and productivity.
For human consumption, cassava tubers are processed in different ways, to prevent cyanide poisoning. Ruminants are less sensitive to feeding on raw plant parts, but through her feeding trials Khuc Thi Hue shows that the leaves are best utilized if the farmers follow a few recommendations.
Lambs can be given fresh cassava foliage in amounts (dry weight) up to 1.5 per cent of their live body weight. When consuming this amount in the morning, after being served another feed, lambs did not exhibit any changes in heart rate, respiration rate or rumen movement. They were also growing and doing well.
An adaptation period of one week is recommended, during which cassava foliage is offered in increasing amounts. An adaptation period of three weeks led to a lower live weight gain.
Khuc Thi Hue also shows that it is possible to reduce the content of hydrogen cyanide by processing cassava foliage through wilting and sun-drying to hay.
In summary, the thesis shows that cassava foliage can be used as a protein source that can replace commercial concentrates, without decreasing the weight gain of sheep. Cassava foliage could also improve the cost-effectiveness of sheep production in Vietnam by reducing feed costs and by controlling nematodes.
____________
MSc Khuc Thi Hue, Department of Animal Nutrition and Management, SLU, defended her thesis Feeding cassava foliage to sheep – Nutrient properties and hydrogen cyanide toxicity on March 29, 2012, at SLU in Uppsala.
More information: Khuc Thi Hue, hienhue02@yahoo.com
Link to the thesis (pdf):
http://pub.epsilon.slu.se/8617/