The Use of Cassava Roots and Leaves for Feeding Pigs in Vietnam

In Vietnam, cassava (Manihot esculenta Crantz) is the second most important food crop after rice in terms of total production; annual root production is about 2 million tonnes, the majority of which is used for animal feeding. Cassava is also an important source of income for poor farmers. Making silage is an appropriate method to preserve cassava roots to be used for pig feeding and is applicable under village conditions. After harvest, fresh roots are cleaned, grated finely and mixed with 0.5% salt. The mixture is put into plastic bags of 20-30 1, pressed tighty to expel all air and tied; it is then let to ferment naturally. The mixture could be used after 2-3 weeks of ensiling and can be kept for at least 3-4 months. Research has shown that including about 40% ensiled cassava roots (ECR) in diets for growing pigs does not affect their growth performance. Under village conditions, the inclusion of 30% ECR of DM of diet improved the daily weight gain and decreased feed cost by 7%. However, a higher proportion of ECR in the diet may cause an imbalance in amino acid concentrations, particularly low methionine. A higher level of digestibility of organic material and crude protein was obtained when including levels of 0.1, 0.2 and 0.3% (as DM) DL-methionine in ECR-based diets for pigs. Inclusion of DL-methionine in the diet significantly reduced the amount of N secreted in urine, increased the retention of N and improved the performance of growing pigs. Although inclusion of DL-lysine (0.1%) and DL-methionine (0.05%) in 30% ERC-based diets did not increase performance, it reduced the feed cost by 3%. At root harvesting time, about 5-7 t/ha of fresh leaves can also be collected. However, leaves are seldom used for feeding animals. The high crude protein content of cassava leaves (2030%) makes these a very useful feed resource. Making silage of cassava leaves reduces the toxicity of HCN and this is a very practical and applicable method. Additives used in the ensiling process are readily available in the village, such as salt, rice bran, molasses and cassava root meal. In diets for growing pigs, inclusion of 15% (as DM) ensiled cassava leaves (ECL) improved daily weight gains and the food conversion ratio, as well as reduced the feed cost by 25%. Additionally, for pregnant sows the feeding with 15% ECL improved their piglet live weight gain at weaning time. In conclusion, cassava roots and leaves can be used effectively for feeding growing pigs and pregnant sows. However, a low protein content of the roots and an imbalance of essential amino acids in the leaves could limit their inclusion in pig diets. INTRODUCTION In Vietnam, cassava (Manihot esculenta Crantz) is the second most important food crop after rice in terms of total production; annual fresh root production is about 2 million tonnes (GSO, 2001), most of which is used for animal feeding. Cassava is also an important source of income for poor farmers. 1 Hue University of Agriculture and Forestry, 24 Phung Hung, Hue City, Vietnam.