科研之友
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摘要
Recently, perennial warm-season grasses have received considerable interest, largely through bioenergy initiatives, but their suitability for limiting caloric intake by fiber-demanding livestock classes, such as dairy replacement heifers (Bos taurus) and/or dry cows has not been explored. Our objectives were to evaluate eastern gamagrass [Tripsacum dactyloides (L.) L.] forages harvested from nine single- or double-harvest systems with four N fertilization regimes for macromineral, protein, and fiber composition, and then to estimate the energy densities for these forages by the summative approach. Across the 3-yr trial, concentrations of neutral-detergent fiber (NDF) from single-harvest systems increased with mostly linear (P < 0.001) and quadratic (P = 0.010) effects of harvest date, reaching maximum concentrations ranging from 746 to 801 g kg(-1) by early or mid-August. Similarly, concentrations of lignin increased with delayed harvest dates across single-harvest systems in predominantly linear (P < 0.001) patterns. Generally, concentrations of lignin were lower than reported for eastern gamagrass forages grown at more southerly latitudes, and ranged from 37.5 to 46.0 g kg(-1) in mid-August. As a result, estimates of total digestible nutrients (TDN) determined by the acid-detergent lignin option for calculating truly digestible fiber remained relatively high through mid-August (582 g kg(-1)). Adjusting truly digestible fiber on the basis of the alternate in vitro 48-h neutral-detergent fiber digestibility (NDFD) approach resulted in reduced TDN estimates for eastern gamagrass. In northern climates, eastern gamagrass forages have large concentrations of NDF, and could be used to dilute dietary energy for livestock species with low or moderate energy requirements.
- 出版日期2010-12
