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 ammo nia lyase (PAL) activity. Whole plants were harvested in Spring 1992 and 19 95 from 4 replicates of each entry and divided into leaf and stem (plus she ath) components for analyses. Entry significantly affected all measurements except PAL; whereas the entry by year interaction significantly affected s tem IVDMD, protein, and PAL. Across entries, stem IVDMD in 1992 (56.3% to 6 6.4%) and 1995 (55.9% to 64.9%) demonstrated greater variation than leaf IV DMD in 1992 (62.2% to 68.0%) and 1995 (66.7% to 71.0%). In 1992 and 1995, a verage leaf IVDMD and protein concentration were generally higher than aver age 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 vari ed more in leaves compared with stems. Stem IVDMD was significantly correla ted with lignin concentration in 1992 (r = -0.92) and 1995 (r = -0.83) as w ell as with protein concentration (r = 0.83) in 1995. Activity of PAL in 19 95 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 varia tion in forage quality, particularly in stems. Potential exists for develop ment of new gamagrass cultivars with high IVDMD and protein.