Open access publications in the SLU publication database

Abstract

The study was aiming to evaluate cassava (Manihot esculenta Crantz) managed as a forage crop with respect to biomass yield, and to determine its value as a feed for monogastric animals. Two common cassava varieties, one short- (ST) and one long-term (LT), grown in Cambodia, were studied with the aim of assessing forage yield, and effects on soil fertility and the utilization of the leaves as a feed for pigs and poultry. The ST variety was intercropped with Desmanthus virgatus or Gliricidia sepium and the LT variety was fertilised with effluent from biodigesters loaded with either cow (CM) or pig manure (PM). Intercropping of cassava with legumes increased total biomass dry matter (DM) yield and resulted in a higher proportion of cassava leaves, while fertilizing with PM produced the highest cassava total forage and leaf DM yields. The crude protein (CP) content on a DM basis in cassava leaf, and stem plus petiole, was 24-25% and 8-10%, respectively. It was estimated that D. virgatus and G. sepium fixed 1/3 and 1/2 of the amounts of nitrogen (N) removed by the cassava forage, respectively, while the N uptake was 67 and 27% above the N inputs from PM and CM, respectively. Both sun-drying and ensiling were efficient in reducing the hydrogen cyanide (HCN) content in cassava leaves, although ensiling after sun wilting was more effective. Pigs utilized the nutrients in cassava leaf silage (CLS) more efficiently than in cassava leaf meal (CLM) and leaves from the ST and LT varieties were utilized equally. Mong Cai (MC) pigs digested dietary fibre components better than Large White x Yorkshire (LxY) pigs, although N utilization was higher in LxY than MC pigs. Increasing CLM level in poultry diets slightly increased DM intake and decreased the digestibility of DM. Increasing dietary CLM increased the weight and length of most parts of the gastrointestinal tract (GIT) and associated internal organs, except for proventriculus weight and colon length. Broiler chickens and White Pekin ducks had higher GIT and internal organ weights and lengths than local ducks and chickens, respectively, when expressed in absolute units. However, when expressed as kg-1 body weight, these values were higher in the local birds, except for small intestine weights, which were similar. Ducks had longer small intestines and higher small intestine, gizzard, pancreas and liver weights as kg-1 body weight than chickens, while weights of caeca and colon, were higher in chickens. It is concluded that both ST and LT cassava varieties have the potential to produce high protein forage for monogastric animals. Pigs utilized cassava leaf silage more efficiently than sun-dried leaves. Increasing cassava leaf meal in the diet reduced DM digestibility and increased the length and weight of most parts of the gastrointestinal tract and associated organs of chickens and ducks.