Kinetic of dry matter ruminal degradation of stem, root, aerial part hay and ureatreated-cassava root silage (Manihot esculenta Crantz)

Abstract

This experiment was carried out at the Southwestern State University of Bahia (UESB), Bahia, Brazil, in order to verify the kinetic of dry matter ruminal degradation of cassava byproducts. Two cows, fistulated in the rumen, were used to incubate samples in nylon bags for 2, 4, 8, 16, 24, 48, 72 and 96 hours, in a completely randomized block design, resulting in four incubation periods for each sample. Tested feedstuffs were cassava root (T1), cassava root silage treated with 3% of urea (T2), cassava aereal part hay (CLH) harvested at 5 (T3) or 14 months of age (T4) and the stems of cassava plants, harvested at 14 months, planted in continuous rows (T5) or 0,6 meters between plants (T6) along the planting line. Percentual results of feed rumen degradabilities (P), were adjusted to the mathematical model "P = a + b (1 - e-ct)". Average percent results found in the treatments were compared using Student-Newman-Keuls test, at the level of 5% of probability. Results for treatments 1 to 6, were respectively: soluble fraction (74,8b; 80,9ª; 26,3c; 23,6d; 22,4d; 22,3d), effective degradability (90,7b; 92,0ª; 65,4c; 62,4d; 41,8e ; 40,9e), potential degradability (99,1ª; 99,4ª; 74,4b; 73,4b; 49,2c; 46,8d) and lag time in hours (0,4cb; 0,1c; 1,5ba; 1,5ba; 1,6ba; 1,8ª). These results indicate a high level of ruminal solubility of cassava root silage treated with urea and a higher degradation rate of CH harvested at 5 months compared to CH harvested at 14 months of age.