Response of two Brachiaria species to swine manure application rates: effect on biomass yield, nutritive quality and acceptability by WAD sheep
Rising inorganic fertilizer prices have led to return to the use of organic nutrient sources to reduce cost and improve pasture productivity. The present study determined the response of Brachiaria ruziziensis and Brachiaria mulato II to swine manure application rates: effect on biomass yield, nutritive quality and acceptability by WAD sheep. The experiment was a 3 × 2 factorial arrangement laid out as a split-plot design with three swine manure application rates (0, 5, 10 t ha-1) as the main plot and two Brachiaria species (B. ruziziensis and B. mulato II) as the sub-plot replicated three times. Growth parameters were determined at 2, 4, 6 and 8 weeks after sowing, while dry matter yield was determined at 8 weeks after sowing. Chemical composition and in vitro gas production of the harvested grass samples were conducted and the acceptability of the forage material by WAD sheep was also determined. Results showed that B. ruziziensis was morphologically taller than B. mulato II at all weeks of growth. The heights of the plants significantly (P < 0.05) increased with increasing manure application rate at all weeks of growth. A significantly (P < 0.05) higher dry matter yield was recorded for B. ruziziensis than in B. mulato (6.24 vs. 4.16 t ha-1). Dry matter yield of the plants increased as the rate of manure application increased. The crude protein content of both grasses increased significantly (P<0.05) as the level of manure inclusion increased. The highest significant (P<0.05) (14.00 ml/200mg DM) gas volume produced was recorded for B. ruziziensis fertilized with 10 t ha-1 of manure while the least gas volume (7.50 ml/200mg DM) was recorded for B. mulato unfertilized at 24 hours of incubation. Brachiaria ruziziensis fertilized with 5 t ha-1 of swine manure was most preferred by the sheep. In conclusion, herbage yield increased as the swine manure application rate increased, also chemical composition and acceptability by sheep was higher in B. ruzuziensis than with B. mulato II.