Crude Protein

The concentration of CP in tall fescue was generally similar to that of orchardgrass, although in a few cases orchardgrass CP was greater (Item A, Table 11-4). When compared in the same study, reed canarygrass, smooth bromegrass, and Kentucky bluegrass generally had greater CP concentrations than tall fescue, regardless of cutting frequency. Management strategies such as frequency of cut, P or N fertilization, and season of cut altered CP concentrations, but the rank among cool-season grass species was retained. With few exceptions, when CP concentrations in tall fescue were low, the CP of other cool-season grasses were also low and, in general, reflected the N status of a particular study.

Differences in CP concentrations among tall fescue cultivars were evident, with Kenhy and ‘Johnstone' generally greater in CP and ‘Stargrazer' the lowest among the cultivars tested (Item B, Table 11-4). Within any of these comparisons, the differences in CP among cultivars were small and, under most conditions, unlikely to be reflected in animal performance. Increasing N applications also increased CP concentrations of the forage (Item C, Table 11-4), as did the application of a growth regulator in June (Item D, Table 11-4). The application of supplemental water, on the other hand, generally reduced CP concentrations


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Table 11-4. Crude protein concentrations in tall fescue compared with other cool-season grasses when harvested for hay or silage.


Dry Matter Disappearance and Fiber Fractions

Tall fescue and orchardgrass had similar DMD for a range of maturities, whereas reed canarygrass, smooth bromegrass, and Kentucky bluegrass had less DMD when harvested infrequently (more mature forage), with differences among species very small when harvested frequently (Item A, Table 11-5). In the latter case, plants remained vegetative, thereby reducing the expression of variation in DMD as a result of morphological differences-variable proportions of leaves as compared to stems. In the numerous comparisons between tall fescue and orchardgrass, tall fescue generally is either greater or similar to orchardgrass in DMD. Noted exceptions are from irrigated production, which showed greater DMD for orchardgrass (615 vs. 566 g/kg). When available, NDF and ADF concentrations generally were related negatively to DMD, with greater fiber concentrations associated with reduced DMD.

The differences among tall fescue cultivars in DMD generally were small and ranged only from 599 to 604 g/kg in a study comparing KY-31, Kenhy, and Johnstone. Differences in TDD among seven cultivars ranged from 785 to 826 g/kg when harvested in July, and from 821 to 854 g/kg when harvested in August (Item B, Table 11-5). Forage concentrations of NDF and ADF also were similar among these cultivars. Nitrogen fertilization generally increased DMD (Item C, Table 11-5) and decreased the fiber fractions.

Soluble Carbohydrates

Although soluble carbohydrate data are extremely limited, those available indicate that large differences can occur among cuttings and among years. Smaller but important differences may occur among cultivars (Item B, Table 11-5). Further, cool environmental conditions favored soluble carbohydrate buildup in the plant and tall fescue showed diurnal variation with soluble carbohydrates increasing from morning through 1800 h (Item D, Table 11-5).


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Table 11-5. Dry matter disappearance (DMD) fiber fractions and soluble carbohydrates (CHO) concentrations in tall fescue when harvested for hay or silage. 




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