Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/1998
Publication Date: N/A
Citation: Interpretive Summary: Forage grasses play a critical role in providing nutrients to ruminants particularly in the more southern regions. The fiber (cell walls) of grasses is poorly digested by ruminants. Increasing the degradation of forage fiber would have a tremendous positive impact on dairy and other animal production systems by providing increased energy, improving protein utilization, and decreasing manure waste. The general approach to improvin grass digestibilities has been to select for lower fiber content while maintaining total dry matter production. This process is not always successful as the fiber portion of the plant is critical for healthy biomass production. Tifton 85 bermudagrass was developed in a breeding program designed to produce cultivars that were more digestible. Tifton 85 has more biomass production with higher fiber concentrations yet is more digestible and produces better animal performance than other cultivars such has coastal bermudagrass. The better performance of Tifton 85 is due to increased cellulose as a digestible component of fiber and decreased lignin concentration within its fiber. These results show that it is possible to select for forage grasses that have increased total dry matter yield yet are more digestible and produce better animal performance. Grasses such as Tifton 85 will have a significant impact upon both beef and dairy animal production systems in warm climates particularly in the south and southeast regions of the United States.
Technical Abstract: A study was undertaken to determine the effects of bermudagrass cultivar and stage of maturity on yields of DM and digestible DM, in vitro digestion, nutrient content, cell wall composition, in situ digestion kinetics, and feed intake and digestion by growing beef steers. Tifton 85 and coastal bermudagrass forages were harvested at weekly intervals from 3 to 8 weeks regrowth. Larger plots were harvested at 3, 5 and 7 weeks regrowth for feeding trials with 36 growing beef steers. Tifton 85 consistently outperformed coastal bermudagrass producing higher DM yields, digestible NDF and digestible ADF. Although Tifton 85 had greater concentrations of NDF, ADF, hemicellulose and cellulose than coastal bermudagrass, steers fed Tifton 85 had higher digestion of DM, OM, NDF, ADF, hemicellulose and cellulose. Digestibilities of both cultivars decreased with increased maturity. In summary, Tifton 85 was higher yielding and more digestible in vitro, in situ, and in vivo than coastal bermudagrass. The optimum stage of maturity to harvest bermudagrass forages in order to maximize yield without loss in digestibility would be between 3 and 5 weeks of regrowth.