Submitted to: Ghana Science Association
Publication Type: Proceedings
Publication Acceptance Date: July 10, 2011
Publication Date: N/A
Interpretive Summary: Silage making is practiced widely in intensive animal production systems in temperate regions, principally for winter feeding and to provide high quality conserved feed all year. Ensiling could be the most suitable method of preserving forage in the tropics because it is independent of weather conditions. Silage preparation could be one of the solutions for addressing the scarcity of good quality forage due to the severe and long dry season experienced in parts of the tropics; however, tropical grasses could lack the protein concentrations to generate sufficient fermentation. One method of improving the protein content of the silage is to add a protein rich legume in mixture with the tropical grass. An experiment was conducted to determine the effect of different percentages of alfalfa in mixture with bermudagrass and switchgrass on nutritive value and fermentation characteristics. Inclusion of 25% alfalfa provided the highest glucose and lactate for both bermudagrass and switchgrass, but the overall quality of the switchgrass silage was better than that of bermudagrass silage. Protein and lactate of silage made with warm-season perennial grasses can be increased with an addition of a high-protein legume to provide 25% of the fresh weight. This management practice could benefit livestock producers in tropical Africa who must preserve low-quality perennial grasses for feeding livestock during their dry seasons when forage production can be extremely low.
Technical Abstract: An experiment was conducted at the University of Kentucky Spindletop Farm in Lexington, Kentucky between October and November, 2009 to evaluate the effect of different percentages of alfalfa (Medicago sativa) as mixtures in switchgrass (Panicum virgatus) and bermudagrass (Cynodon dactylon) silages. Switchgrass and bermudagrass were ensiled separately and each were in combination with four percentages of alfalfa (0%, 25%, 50% and 75% w/w). The alfalfa percentages were on a fresh material basis. The alfalfa was thoroughly mixed with the grasses and put in micro laboratory silos of dimension 4- by 14-inch PVC pipes with rubber caps on each end. Three replicates of the mini-silos were used for each treatment. Following a 30-day fermentation, the laboratory silos were opened and sampled. Percentages of dry matter (DM), neutral detergent fiber, acid detergent fiber, crude protein, and in vitro dry matter digestibility were determined. Fermentation characteristics of the silages such as pH, lactate, acetate, butyrate, glucose, and ethanol were also determined. Crude protein, in vitro digestibility and fiber components increased with increases in percentage of alfalfa in the mixture. The 25% alfalfa inclusion for switchgrass, had higher lactate and glucose compared to the other treatments. The pH of 25% (pH= 4.7) and 50% (pH = 4.6) alfalfa inclusions for switchgrass were not different from each other but were lower than the other treatments. As alfalfa percentages increased from 0% to 75%, lactate content of bermudagrass reduced from 5.4 to 1.6 mM. Glucose and lactate were higher for bermudagrass silage with 0% and 25% alfalfa. Bermudagrass silages were generally low in quality (most pH above 5). Due to the poor quality of bermudagrass-alfalfa silages, further nutrient analysis was not performed. Switchgrass silage benefitted most from addition of alfalfa with the 25% alfalfa inclusion being the best in terms of lactic acid production.