Quality improvement of sweet-potato (Ipomoea batatas L. Lam.) roots as feed by ensilage.

1. Sweet-potato (Ipomoea batatas L. Lam.) strips (SPS) mixed with maize powder (CP) in proportions 10:0, 9:1, 8:2, and 7:3 were ensiled for 1, 2 or 3 months. 2. Trypsin inhibitor activity (TIA) decreased during ensilage in samples of all treatments while the SPS-CP mixture (7:3, w/w) ensiled for 3 months contained the lowest TIA. 3. SPS-CP (8:2, w/w) dried or ensiled for 2 months, or ensiled for 2 months and dried, were each mixed with twice the amount of control diet (1:2, w/w) to make three diets. These three diets together with the control diet were used for a feeding experiment with rats to evaluate the nutritive value. 4. General composition analysis (including metabolizable energy), fatty acid composition and amino acid analysis (including percentage of essential amino acids) of the samples did not change during ensilage to an extent which could explain the improved performance of rats fed on ensiled diets. 5. Rats fed on diets containing dried SPS-CP (8:2, w/w) showed significantly lower (P less than 0.05) body-weight gain than rats fed on the control diet or ensiled SPS diets, at the end of the 8th week. They also showed enlargement of the pancreas. The adverse effect of SPS was associated with TIA which seemed to be prevented to some extent by ensilage. 6. The possibility that the starch of SPS may also contribute to the adverse effect cannot be excluded at present.