Kinetics of ruminal degradation of alfalfa and Tifton-85 hays, and of corn Silage

Abstract

This study aimed at evaluating the ruminal degradability and the rate of in-situ degradation of dry matter (DM), of crude protein (CP), of neutral detergent fiber (NDF), of alfalfa and Tifton-85 hays, and of corn silage. Three fistulated cows were used. The cows were adapted for 15 days to the three diets mentioned above. The diets were incubated in nylon sacks for 3 days. The following incubation times were used: zero, 2, 6, 12, 24, 48 and 72 hours. After the removal, the sacks were washed lightly in running water and soon after frozen until the complete removal of the others. The effective degradability (ED) of dry matter (DM), of crude protein (CP) and of neutral detergent fiber (NDF) of the alfalfa hay showed themselves superior (P<0.05) to the Tifton-85 hay and the corn silage. Considering a passage rate of 5 and 8% per hour, the potential (PD) and effective (ED) degradability of DM, of CP and of NDF were, respectively, of: 80.18, 59.91 and 54.39%; 94.0, 71.11 and 63.16%; 61.64, 35.72 and 29.72% for the alfalfa hay; 70.34, 36.57 and 30.60%; 74.12, 32.79 and 25.29%; 67.74, 30.33 and 23.58% for the tifton-85 hay; and 75.95, 47.34 and 41.99%; 78.57, 61.11% and 57.42; 64.89, 28.84 and 22.05% for the corn silage. The highest rate of dry matter (DM) degradability of the potentially degradable fraction (c) found for the alfalfa hay (6.45% per hour) indicates that this material degrades fraction "b" faster than the other analyzed feed.