Leaves from varieties of cassava (Manihot esculenta Crantz) growing in South Vietnam were collected at the time of harvesting the roots and analysed for their nutrient and cyanide content. Nutritional properties of the dried and ensiled cassava leaves were determined with pigs and rats.
The crude protein of cassava leaves ranged from 240 to 350 g/kg, and the crude fibre from 100 to 150 g/kg on a dry matter basis. It was found that the HCN content was markedly reduced by both drying and ensiling, with the reduction being highest after sun-drying and oven-drying. The ileal and total tract apparent digestibilities in pig and rats of organic matter, crude protein, nitrogen free extractives and energy, and nitrogen retention, were negatively affected by inclusion of cassava leaves. The impaired amino acid profile after drying cassava leaves at 105 oC was found to be related to a slight decrease in digestible protein as well as N retention. Average ileal digestibility coefficients of organic matter, crude protein and crude fibre in cassava leaves were 0.42, 0.37 and 0.35; total tract digestibility coefficients were 0.57, 0.46 and 0.55, respectively. The average digestible energy content was 11.7 MJ/kg DM and average apparent ileal digestibility of essential amino acids was 0.56.
It was concluded that, under tropical conditions, the low levels of inclusion of leaves from mature cassava plants may be useful in diets for growing pigs to improve the dietary protein supply. Sun-drying and ensiling with cane molasses as additive successfully preserved the nitrogenous constituents and could be a means of preserving fresh green feed.