Intake and nutritive value of florigraze rhizoma peanut silage for lactating dairy cows.

Florigraze rhizoma peanut (Arachis glabrata Benth.) is a very persistent, high quality legume that is well adapted to subtropical and tropical environments. This legume was ensiled and compared with corn silage (Zea mays) as a feedstuff for lactating dairy cows. Twelve Holstein cows, including 4 ruminally fistulated cows (mean, 70 days in milk), were used in an experiment with a 4 x 4 Latin square design replicated three times. Diets were formulated to contain 50% concentrate on a dry matter (DM) basis. Dietary treatments were rhizoma peanut silage and corn silage fed at DM ratios of 0:50, 20:30, 35:15, and 50:0. The dry matter intake, digestibilities of DM and crude protein, and production of milk and fat-corrected milk decreased quadratically as the percentage of legume in the diet increased. Nearly all of the decrease occurred when rhizoma peanut silage was the sole forage in the diet. The organic matter digestibility of the two forage types was similar; however, digestion of crude protein in rhizoma peanut silage was only 45% (calculated using simultaneous equations). Ruminal pH increased, and ammonia and total volatile fatty acid concentrations decreased, as the percentage of rhizoma peanut silage in the diet increased. In situ digestion rate constants for DM of rhizoma peanut silage were twice that of corn silage, but extent of DM digestion was greater for corn silage. Passage rates of concentrates and forage were unaffected by dietary treatments. Rhizoma peanut silage can replace 70% of corn silage in diets containing 50% concentrate without affecting dairy cow performance.