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In Vivo Quality of Tall Fescue as Influenced by Season, Legumes, Age, and Canopy Strata

Rayburn, E. B., Blaser, R. E., Fontenot, J. P.
Agronomy journal 1980 v.72 no.6 pp. 872-876
Dactylis glomerata, Festuca arundinacea, Medicago sativa, Trifolium pratense, alfalfa, animal performance, application rate, ash content, canopy, climate, digestibility, digestible dry matter, dormancy, dry matter accumulation, economic impact, forage, grazing, lignin, regrowth, sheep, summer, winter
Fall-grown tall fescue (Festuca arundinacea, Schreb.) provides a relatively inexpensive forage for winter grazing. Quality and yield of actively growing tall fescue increases when accumulated from August and harvested through time in the early fall. The effect of regrowth age on fall accumulated tall fescue quality has not been evaluated under similar harvest climates and animal performance on summer grown tall fescue is often low. Therefore a series of experiments were conducted to evaluate the in vivo quality of tall fescue in summer, alone and in combination with a legume, and to evaluate the in vivo quality of tall fescue of different regrowth ages harvested in December. Summer grown tall fescue, alfalfa (Medicago sativa L.) and red clover (Trifolium patense L.) were fed alone and compared with 50:50 mixes of each legume with tall fescue. Orchardgrass (Dactylis glomerata L.) was also fed alone and with red clover during 1 year. Low in vivo digestible dry matter (DDM) of 35.8% for tall fescue 60 days old in 1975 was associated with droughtimposed dormancy. Nondormant, 40-day-old alfalfa regrowth was highly digestible (59.4% DDM). In 1976, the digestibilities of tall fescue and red clover were similar (54.8 and 53.9% DDM) and lower than that of orchardgrass (57.0% DDM). Consistent, nonsignificant trends in increased digestibility occurred with the inclusion of a legume which were sufficiently large to have potential economic consequences on animal production. In another experiment, tall fescue was accumulated from mid-June, July, August, and September, with 112 kg N/ha applied in mid-August, to evaluate the influence of age on in vivo quality when fed to sheep in early December. Quality decreased with increasing age. In 1975, June accumulated forage was significantly lower in quality than forage with shorter accumulation periods. In 1976, quality decreased with increased ages of the accumulated growth, ranging from 51.0 to 60.5% DDM for June and August accumulated forage, respectively. Quality of September accumulated forage was low (52.8% DDM), apparently due to high lignin and insoluble ash contents. Improved quality with shorter accumulation periods was offset by lower dry matter yields (5.2 vs. 2.2 metric tons/ha) and DDM yields were also reduced (1.7 vs. 1.2 metric tons/ha) from June to September, respectively. Accumulating tall fescue from as early as mid July did not decrease digestibility or intake sufficiently to make this practice impractical for winter grazing. Summer utilized tall fescue was lower in quality than that utilized in winter. There were significant correlations between DDM and TNC contents.