Determination of the Nutritive Value of Tropical Biomass Products for Monogastrics Using Rats: 2. Effects of Drying Temperature, Ensiling and Level of Inclusion of Cassava Leaves and Sweet Potato Vines

  • Phuc, Bui Huy Nhu ;
  • Lindberg, Jan Erik ;
  • Ogle, Brian ;
  • Thomke, Sigvard
  • Received : 2000.10.04
  • Accepted : 2001.02.19
  • Published : 2001.07.01


In a balance experiment with rats either 0, 25 or 50% of the crude protein (CP) provided as casein in the control diet was replaced with cassava leaves (CL) (Manihot esculenta Crantz) or sweet potato vines (SPV) (Ipomoea balala). CL were either sun-dried or oven-dried at $60^{\circ}C$ or $105^{\circ}C$ or ensiled, while the SPY were either sun-dried or ensiled. The experiment included 3 blocks with 30 rats in each and six individuals per treatment group. Drying at $105^{\circ}C$ resulted in a reduction of the lysine (Lys) content, suggestive of the occurrence of Maillard reactions. Ensiling CL and SPV slightly decreased the CP. content as well as the sum of essential amino acids. The apparent fecal CP digestibility (dCP) and nitrogen retention were negatively affected by increasing the level of replacement (p<0.01 and p<0.001, respectively). The impaired amino acid profile observed when drying CL at $105^{\circ}C$ was found to be related to a slight decrease in dCP (p<0.001) as well as N retention (p<0.005). The effects of sun-drying and oven-drying in reducing the HCN content in CL were more potent than when ensiling. By increasing the total dietary HCN supply serum thiocyanide level, as well as urinary thiocyanate and linamarin output, were increased, with a weak relationship between them. Sun-drying and ensiling with cane molasses as additive successfully preserved the nitrogenous constituents and could be a means of preserving fresh green feed under tropical conditions.


Tropical Biomass;Nutrient Digestibility;Biological Value;Rats;Drying;Ensiling;Protein Quality

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Supported by : Swedish Agency for Research Co-operation (Sida - SAREC)