Intake and rumen degradation in cattle fed napier grass (Pennisetum purpureum) supplemented with various levels of Desmodium intortum and Ipomoea batatus vines

This study was conducted to assess the effect of greenleaf desmodium (Desmodium intortum) and sweet potato vine (Ipomoea batatus) supplementation of napier grass on dry matter intake, degradation and rumen fermentation in Friesian steers. Four fistulated steers were offered napier grass diets containing 0, 10, 20 or 30% desmodium or sweet potato vine in two 4 x 4 latin squares. Organic matter intake per kg metabolic body weight increased linearly with increasing inclusion level of desmodium (74-90 g/ kg(075)) and sweet potato vine (78-94 g/kg(0.75)). Crude protein intake also increased linearly with the increase in inclusion level of desmodium (7.6-13.0 g/kg(0.75)) and sweet potato vine (7.9-12.9 g/kg(0.75)). Supplementation improved DM degradation but did not change rumen pH. Rumen fermentable organic matter increased by up to 52% and 43% for desmodium and sweet potato vine respectively at the highest levels of supplementation. Ammonia nitrogen concentrations increased with increasing level of desmodium (130-214 mg/l) and sweet potato vine (139-235 mg/l). Inclusion of desmodium and sweet potato vine led to small increases in concentrations of total and individual volatile fatty acids. It was concluded that the two forage supplements could play an important role in improving animal performance when napier grass is fed as the basal diet.