Thursday, April 27, 2017
How to use cassava as a global livestock feed ingredient.
Cassava known mostly for its starch-rich tubers is a plant that also offers many possibilities to provide other lesser-known feed ingredients for man and livestock. Cassava is a plant that is very tolerant to poor growing conditions as it can be cultivated in regions suffering from poor soil, droughts and even frequent plant diseases. Under such conditions, it yields about 13 metric tons of tubers per hectare. Of course, when grown in near-ideal (tropical) conditions, yield can reach up to 80 metric tons of tubers per hectare. Cassava is the second largest carbohydrate-rich crop worldwide, with over 9 million hectares of cultivated land devoted to cassava production in Africa and Asia. Global cassava cultivation expands to Asia, Latin America and Africa due to high demands from the human, feed, industrial starch and ethanol industries. Thailand is the largest exporting country for cassava products but surpassed by Nigeria and Brazil, two countries that use their local cassava internally. Nigeria has used cassava extensively as food for man,making different products such as garri,tapioca, cassava chips,starch and flour. Cassava has also made an entrance to livestock feed to boost productivity and reduce cost of production by using local feed. Cassava peels and cassava root meal have been explored in livestock with good results,see The cyanide content of the plant is the major reason why many farmers are skeptical about using it but processing reduces the cyanide content and also cyanide content varies with cassava specie making the inclusion in livestock feed safe .There are two types of cyanogenic glucosides in cassava: linamarin and lotaustralin, the first making up to 93 percent of total. When animals eat the raw cassava tubers or leaves ,they consume the cyanogenic compounds thus releasing the cyanide which is highly toxic to animals causing asphyxia and death. Processing the cassava removes the cyanide thus emphasis is on proper processing, when the cassava peels are sun dried or oven dried, linamarase enzyme is released and this comes into contact with the cyanogenic glucosides and releases hydrogen cyanide (HCN), which is volatile and evaporates, and because sun drying takes longer time span than oven it releases more of cyanide which makes the peels safe. The processing removes as much as 90% by this processing method.The raw cassava pulp contains as much as 200 mg/kg HCN, whereas these levels are reduced to 31 and 27 mg/kg, by oven-and sun-drying, respectively. The whole tuber contains as much 400 mg/kg HCN, with the peel containing as much as 800 mg/kg. The leaves are even richer in this compound, containing up to 1,500 mg/kg. There are several varieties of cassava, ranging from 75 to 1,000 mg/kg HCN, and factors such as soil conditions, fertilizer and weather also affect the concentration of HCN, so choosing the variety with the minimum cyanide content will be a factor to jump start the processing for safety. Cassava leaves can also used as feed ingredient but must be dried and milled to create cassava leaf meal, a material rich in protein and fiber but low in energy. The inclusion in feed must be with extra caution because of the very high levels of HCN in raw leaves. The high level of cyanide in leaves can be reduced by proper processing, timing of the harvest and appropriate variety selection. 10 metric tons dried cassava leaf meal can be produced per hectare, this is a significant by-product, suited especially as an animal feed.