Forage quality of 10 Eastern gamagrass [Tripsacum dactyloides (L.) L.] genotypes

Ten eastern gamagrass [Tripsacum dactyloides (L.) L.] entries from Kansas, Oklahoma, and Texas, were evaluated for in vitro dry matter digestibility (IVDMD), protein concentration, lignin concentration, and phenylalanine ammonia lyase (PAL) activity. Whole plants were harvested in Spring 1992 and 1995 from 4 replicates of each entry and divided into leaf and stem (plus sheath) components for analyses. Entry significantly affected all measurements except PAL; whereas the entry by year interaction significantly affected stem IVDMD, protein, and PAL. Across entries, stem IVDMD in 1992 (56.3% to 66.4%) and 1995 (55.9% to 64.9%) demonstrated greater variation than leaf IVDMD in 1992 (62.2% to 68.0%) and 1995 (66.7% to 71.0%). In 1992 and 1995, average leaf IVDMD and protein concentration were generally higher than average stem IVDMD and protein concentration. In 1992, lignin concentration was generally higher and varied more in stems (3.27% to 4.99%) than in leaves (3.54% to 4.11%). In 1995, lignin concentration was about the same and varied more in leaves compared with stems. Stem IVDMD was significantly correlated with lignin concentration in 1992 (r = -0.92) and 1995 (r = -0.83) as well as with protein concentration (r = 0.83) in 1995. Activity of PAL in 1995 was correlated with stem IVDMD and protein. When all data were combined, IVDMD was significantly correlated with protein concentration (r = 0.82). These results indicate that gamagrass entries demonstrate significant variation in forage quality, particularly in stems. Potential exists for development of new gamagrass cultivars with high IVDMD and protein.