Fermentation characteristics and nutritive value of low moisture silage made from mature bermudagrass (C. dactylon) and switchgrass (P. virgatum) in mixture with alfalfa (M. sativa) or treated with urea and plantain (Musa AAB)

Abstract

Two experiments were 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, and also to investigate the effect of plantain and or urea as additives in switchgrass and bermudagrass silages. Mini-silos of dimension 10.16 cm × 35.56 cm with PVC pipes and rubber caps on each end were used. In the first experiment, switchgrass and bermudagrass were ensiled separately in combination with four percentages of alfalfa (0%, 25%, 50% and 75 %) on fresh weight basis. In the second experiment, switchgrass and bermudagrass were ensiled with or without urea (6 or 12 g/ 6 kg of grass) and or plantain (200 or 400 g/ 6 kg of grass) as additives. The alfalfa or additives were thoroughly mixed with the grasses and put in the micro-laboratory silos. Three replicates of the mini-silos were used for each treatment. After a 30-day fermentation, the laboratory silos were opened and sampled. Dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), and in vitro dry matter digestibility (IVDMD) were determined, in addition to fermentation characteristics of the silages such as pH, lactate, acetate, butyrate, glucose, and ethanol. The results indicated that increased alfalfa percentages in the mixture resulted in increased, CP and digestibility of the switchgrass silage. The 25 per cent alfalfa inclusion for switchgrass, had significantly (P ≤ 0.05) higher values for lactate contents compared to the other treatments. The 50 per cent alfalfa inclusion for switchgrass had the lowest pH (4.6). As alfalfa percentages increased from 0 per cent to 75 per cent, lactate content of bermudagrass silages was reduced from 5.4 to 1.6 mM. The lactate content was significantly (P ≤ 0.05) higher for bermudagrass silage with 0 per cent and 25 per cent alfalfa. Bermudagrass silages were generally low in quality (pH above 5).The lactate contents of the bermudagrass were generally lower than that of the switchgrass in the second experiment. The urea + plantain combinations resulted in the highest lactate values and lowest pH values (4.2 – 4.4) for switchgrass. Switchgrass silage benefitted most from addition of alfalfa, urea and plantain. The silage quality of switchgrass could be improved with addition of 25 – 50 per cent alfalfa or addition of urea (6 or 12 g/6 kg grass) in combination with plantain (200 or 400 g /6 kg grass). The use of plantain alone as an additive can improve silage quality of bermudagrass, and legume can be mixed with switchgrass to enhance silage quality.