Submitted to: Professional Animal Scientist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/24/2003
Publication Date: 5/15/2004
Citation: Eun, J., Fellner, V., Burns, J.C., Gumpertz, M.L. 2004. Eastern gamagrass evaluated as hay or silage for lactating dairy cows.. Professional Animal Scientist 19:362-369. Interpretive Summary: In the Southwestern USA corn silage and alfalfa harvested as hay or silage has been the major forages used in dairy rations. The use of a perennial forage that could be used in place of the annuals or short-lived perennials and one that would benefit both the environment and wildlife diversity would be very advantageous. Gamagrass, a long-term perennial native grass, was evaluated by lactating dairy cows to assess its potential as a substitute for corn silage and alfalfa. Ensiled gamagrass, compared with gamagrass preserved as hay, maintained its nutritive value well giving better feed efficiencies. Further, due to the extensively fermentable fiber and the associated N within the cell wall, milk urea N concentrations was less for silage compared with hay resulting in greater efficiencies of N utilization. The addition of corn to the gamagrass silage diet increased total dry matter intake and improved utilization of N over gamagrass fed alone. Including corn up to 50% of the gamagrass-based silage supported high milk yields without causing milk fat depression. Gamagrass ensiled well, was well consumed by cattle and offers potential to replace both corn and alfalfa for diary cattle enterprise.
Technical Abstract: Traditional forage sources for dairy cattle production in the southeastern US can be substituted with warm-season perennial grasses. This study was conducted to determine nutritional value of eastern gamagrass [Tripsacum dactyloides (L.) L.] as a single forage source for dairy diets. Twenty lactating Holstein cows were used to test the treatments that consisted of 1) gamagrass hay (H) and no corn (HNC), 2) gamagrass silage (S) and no corn (SNC), 3) S and low corn (SLC), 4) S and medium corn (SMC), and 5) S and high corn (SHC). Feeding gamagrass as hay or silage did not change milk yield (27.6 vs. 29.5 kg/d). Compared with SNC, feeding corn tended to increase milk yield at the medium or high level of corn inclusion (28.9 vs. 35.2 kg/d; P < 0.08). Milk fat, and lactose concentrations were similar across all treatments. There was a tendency for milk protein concentration to be greater with SHC (P < 0.07). Yields of milk protein (0.69 vs. 0.80 kg/d), lactose (1.23 vs. 1.44 kg/d), and SNF (2.12 vs. 2.48 kg/d) tended to be greater with SNC compared with HNC (P < 0.08) and corn inclusion supported greater milk yields when compared to SNC. Gamagrass fed as silage resulted in a greater feed conversion efficiency compared to gamagrass fed as hay (2.16 vs. 1.88; P < 0.01). Adding corn to S resulted in a lesser feed efficiency. Conversion of feed N to milk N was greater (P < 0.01) with gamagrass fed as silage compared to hay. Milk urea N (MUN) concentration was greater (P < 0.01) for cows fed HNC compared to all other treatments. Feeding S significantly lessened MUN concentration, and corn included at the medium and high levels further reduced MUN concentration (P < 0.05). Increased energy from corn at the high level increased milk yield and tended to increase conversion of feed N into milk protein. Gamagrass fed as silage without or with corn improved the N status of the cows as indicated by lesser MUN concentrations.