NUTRITIONAL VALUE OF EASTERN GAMAGRASS CONSERVED AS HAY OR SILAGE.

Authors: EUN, JONG-SU - NORTH CAROLINA STATE UNIV; Burns, Joseph; FELLNER, VIVEK - NORTH CAROLINA STATE UNIV; GUMPERTZ, MARCIA - NORTH CAROLINA STATE UNIV

Submitted to: Eastern Native Grass Symposium
Publication Type: Proceedings
Publication Acceptance Date: 3/20/2003
Publication Date: 10/15/2004
Citation: Eun, J., Burns, J.C., Fellner, V., Gumpertz, M.L. 2004. Nutritional value of eastern gamagrass conserved as hay or silage.. Eastern Native Grass Symposium. 3rd, Chapel Hill, NC. 1-3 Oct. 2002. Omnipress, Madison, WI.

Interpretive Summary: Eastern gamagrass (Tripsacum dactyloides (L.) L.), a native, warm-season, perennial tall grass, was evaluated for its potential as a forage source in dairy rations. Twenty lactating Holstein cows were fed gamagrass hay or silage without or with supplemental corn to determine effects on milk production. Diets fed in the production trial were also used in continuous cultures to evaluate effects on ruminal fermentation. Diets consisted of gamagrass hay (GH), gamagrass silage (GS), gamagrass silage + low corn (GSLC), gamagrass silage + medium corn (GSMC), and gamagrass silage + high corn (GSHC) with CP levels similar across treatments. Conserving gamagrass as hay or silage did not affect milk yield. Feeding supplemental corn increased milk yield but only at the medium and high levels of corn inclusion (P < 0.05). Milk fat, protein, and lactose contents were similar across all treatments; there was a tendency for milk protein to be higher with GSHC diet (P < 0.07). Gamagrass silage increased the conversion of feed N to milk N compared to gamagrass hay (P < 0.01). Contrary to expectation, conserving gamagrass as silage lowered milk urea nitrogen (MUN) compared to hay. Supplemental corn further reduced MUN concentration. Increasing the level of corn supplementation in GS linearly decreased culture pH (P < 0.04) whereas NH3-N was similar across treatments (27.9 mg/100 ml). Reduced concentrations of MUN are indicative of improved N status of cows. Difference in N efficiencies for cows fed gamagrass as hay or silage may be related to changes in the protein fraction during the conservation process. Key Words: Eastern gamagrass, Corn, Dairy cows, Continuous cultures

Technical Abstract: Eastern gamagrass (Tripsacum dactyloides (L.) L.), a native, warm-season, perennial tall grass, was evaluated for its potential as a forage source in dairy rations. Twenty lactating Holstein cows were fed gamagrass hay or silage without or with supplemental corn to determine effects on milk production. Diets fed in the production trial were also used in continuous cultures to evaluate effects on ruminal fermentation. Diets consisted of gamagrass hay (GH), gamagrass silage (GS), gamagrass silage + low corn (GSLC), gamagrass silage + medium corn (GSMC), and gamagrass silage + high corn (GSHC) with CP levels similar across treatments. Conserving gamagrass as hay or silage did not affect milk yield. Feeding supplemental corn increased milk yield but only at the medium and high levels of corn inclusion (P < 0.05). Milk fat, protein, and lactose contents were similar across all treatments; there was a tendency for milk protein to be higher with GSHC diet (P < 0.07). Gamagrass silage increased the conversion of feed N to milk N compared to gamagrass hay (P < 0.01). Contrary to expectation, conserving gamagrass as silage lowered milk urea nitrogen (MUN) compared to hay. Supplemental corn further reduced MUN concentration. Increasing the level of corn supplementation in GS linearly decreased culture pH (P < 0.04) whereas NH3-N was similar across treatments (27.9 mg/100 ml). Reduced concentrations of MUN are indicative of improved N status of cows. Difference in N efficiencies for cows fed gamagrass as hay or silage may be related to changes in the protein fraction during the conservation process. Key Words: Eastern gamagrass, Corn, Dairy cows, Continuous cultures