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© 2008 Plant Management Network. Use of Limpograss in Grazing Systems in Florida J. M. B. Vendramini, Agronomy Department, J. D. Arthington, Department of Animal Sciences, Range Cattle Research and Education Center, Ona, FL 33865; and W. F. Brown, Department of Animal Science, University of Florida, Gainesville, FL 32611 Corresponding author: J. M. B. Vendramini. jv@ufl.edu Vendramini, J. M. B., Arthington, J. D., and Brown, W. F. 2008. Use of limpograss in grazing systems in Florida. Online. Forage and Grazinglands doi:10.1094/FG-2008-1212-01-RV. Abstract In South Florida, perennial tropical grasses become dormant in the fall and decline in nutritive value rapidly after first frost. The need to identify forages that produce significant herbage mass in the winter months is of major importance to cattle producers in order to reduce the need for stored forage or annual crops. Limpograss [Hemarthria altissima (Poir.) Stapf and C. E. Hubbard] produces greater herbage mass than other tropical grasses during the fall-winter and generally contains greater total digestible nutrients (TDN) concentration than other tropical grasses at late maturity. However, the whole plant of limpograss can have reduced crude protein (CP) concentrations and the plant parts vary widely in their nutritive value. In most cases, the limpograss leaf is balanced in terms of its TDN:CP (7.0 or less), while the stem is unbalanced (decreased CP relative to energy). Generally, ruminants grazing limpograss respond positively to CP supplementation when the diet is composed of relatively greater proportions of stem material, thereby having a greater TDN:CP (generally greater than 9.0). Limpograss is a valuable warm-season grass species for heifer development programs and cow-calf production systems in South Florida. Introduction First extensively evaluated in 1974, ‘Floralta’ limpograss is the most widely utilized of the available limpograss varieties in South Florida. This tropical grass originates from the Limpopo River in the Republic of South Africa. Floralta is a stoloniferous perennial tropical grass that was specifically selected for its persistence under grazing conditions. Limpograss can withstand short periods of seasonal flooding and grows best in areas of soils with greater clay concentrations, which retain moisture. Limpograss produces very little seed and is established through vegetative propagation. A 1998 survey of cattle producers in South Florida revealed that 79% of beef operations fed stored forage in the winter and early-spring months (13). Due to unpredictable weather with frequent rain during the growing season, production of stored forage can be very difficult in many areas of South Florida. In addition, escalating fuel costs make stored feed production and annual forages less economically attractive. The need to identify forages that produce significant herbage mass in the winter months is of major importance to cattle producers in South Florida to reduce the need for stored forage or annual crops. Floralta has superior winter yield compared to other warm season perennial grasses, primarily in poorly drained soils. In addition, limpograss can be expected to produce as much as 30 to 40% of its annual growth during the winter months (5). Limpograss utilization has been limited in South Florida because it does not persist under extended periods of temperatures below freezing (0°C). The objective of this review is to summarize existing research on limpograss utilization in grazing systems in order to provide a useful reference document for forage researchers and extension specialist in the southeastern USA. Nutritive Value of Limpograss A distinct characteristic of limpograss as compared with other tropical grasses is the maintenance of energy value with advancing maturity during the growing season. Sollenberger et al. (11) used steers to graze ‘Pensacola’ bahiagrass (Paspalum notatum Flugge) and Floralta limpograss pastures during the summer and early fall. At all sampling dates, in vitro digestible organic matter (IVDOM) of limpograss pasture (whole-plant samples) was approximately 100 g/kg greater than that of bahiagrass pasture (Table 1). Although limpograss is usually greater in energy value than most other tropical grasses at similar regrowth intervals, crude protein (CP) concentration decreases significantly. At each sampling date, CP concentration of limpograss was much lower than that of bahiagrass, and lower than levels thought to limit intake and gain (6). Limpograss also has a more rapid growth rate compared to many tropical grasses, and at each sampling date herbage mass of limpograss pasture was greater than that observed from bahiagrass pasture. Table 1. In vitro digestible organic matter (IVDOM), crude protein (CP), and herbage mass of bahiagrass and limpograss (“Bahia” and “Limpo,” respectively) pastures during the grazing season.x
x Data from Sollenberger et al. (11). Moore et al. (7) utilized sheep in feeding trial to estimate voluntary intake and digestibility of various tropical grasses at 4, 6, and 8 weeks of regrowth. Nutritive value, including TDN concentration of the grasses was determined at each measurement (Table 2). At each regrowth interval, sheep consumed more limpograss hay compared to the other tropical grass hays with the exception of stargrass hay at 8 weeks regrowth interval. Further, the TDN concentration of limpograss hay was greatest regardless of the regrowth interval, resulting in greater intake of total digestible nutrients for limpograss relative to the other hays, with the exception of stargrass hay at 8 weeks regrowth interval. Table 2. Intake and digestibility of tropical grass hays harvested after 4, 6, and 8 weeks regrowth.x
x Data from Moore et al. (7). y Grams per unit of metabolic weight. Abbreviations: OMI = organic matter intake; TDN = total digestible nutrients; TDNI = total digestible nutrients intake; BW = body weight; DM = dry matter; and MW = molecular weight. The increased energy value, intake potential, and growth rate of limpograss relative to bahiagrass led Sollenberger et al. (11,12) to hypothesize that cattle grazing limpograss would gain more weight than those grazing bahiagrass, and that limpograss pasture would have a greater carrying capacity than bahiagrass pasture. To investigate this, yearling steers (239 to 299 kg) were used to graze limpograss and bahiagrass pastures using either continuous (11) or a rotational (12) stocking. When pastures were stocked continuously, steer average daily gain (ADG), carrying capacity, and gain per hectare (gain/ha) were similar between limpograss and bahiagrass pastures (Table 3). When pastures were grazed in a rotational stocking, ADG by steers was similar between limpograss and bahiagrass pastures; however, limpograss pastures had a greater stocking rate and consequently gain/ha as compared to bahiagrass pastures. Table 3. Yearling steer ADG, carrying capacity, stocking rate, and gain/ha on bahiagrass and limpograss ("Bahia" and "Limpo," respectively) pastures grazed in a continuous or rotational stocking.x
x Data from Sollenberger et al. (11,12). y Treatments within grazing method are not different (P > 0.05) Forage and Canopy Composition and Response to Protein Supplementation A database developed by Moore et al. (8) from a large number of publications involving CP supplementation of temperate and tropical grasses and crop residues revealed that forages with TDN:CP ratios of 7.0 or greater contained marginal CP relative to TDN, and positive responses to CP supplementation were found in many cases. Limpograss plant parts vary widely in their nutritive value. In most cases, the limpograss leaf is balanced in terms of its IVDOM:CP ratio, while the stem is unbalanced (low CP relative to energy) (10). This relationship can have profound effects on grazing management strategy and potential responses to CP supplementation. Pitman et al. (10) used yearling cattle to graze Floralta limpograss at a stocking rate which resulted in herbage mass from 10,000 to 15,900 kg DM/ha, similar to those observed by Brown and Adjei (1). Samples representing the diet consumed by animals obtained from esophageally fistulated steers were separated into leaf and stem fractions. Leaf and stem samples were similar in IVDOM (547 vs. 525 g/kg for leaf and stem, respectively); however, leaf samples were much greater in CP concentration than the stem (84 vs. 27 g/kg for leaf and stem, respectively). This resulted in IVDOM:CP values of less than 7.5 for the leaf, but greater than 16 for the stem. The authors noted that at the grazing pressures utilized, the upper grazed portion of the canopy was composed primarily of leaf material with a stemmy stubble layer which formed at the base of the canopy. This stubble layer was mostly ungrazed by cattle unless forage availability declined to a low enough level which forced cattle to graze from this horizon. To investigate the influence of limpograss canopy structure and composition on the response to CP supplementation, Newman et al. (9) varied animal stocking density to establish three canopy heights (20, 40, and 60 cm), thereby altering forage availability and nutritive value. Yearling heifers (340 kg) grazed these three pasture treatments and were either fed no CP supplement or 0.6 kg of a corn-urea supplement containing 440 g/kg CP on a DM basis. For heifers fed no supplement, ADG responded in a quadratic manner with increasing canopy height (Table 5). For these heifers, ADG increased as canopy height increased from 20 to 40 cm, but then decreased as canopy height increased further to 60 cm. The decrease in ADG between the 40- and 60-cm canopy heights was attributed to trampling and lodging of accumulated limpograss forage at the 60-cm pasture canopy height. An interaction existed between canopy height and CP supplementation. At the 20- and 60-cm canopy heights, CP supplementation improved ADG, while at the 40-cm canopy height, providing a CP supplement did not influence ADG. The positive response to CP supplementation in heifers grazing the 20- and 60-cm canopy heights was attributed to reduced intake of limpograss leaf, although for different reasons. At the 20-cm canopy height, bulk density of both total forage and leaf was greater than other canopy heights; however, the authors suggested that the close association of leaf with stem made it difficult for cattle to select the leaf without consuming the stem. At the 60-cm canopy height, trampling and lodging reduced the bulk density and percentage of leaf in the upper layer, perhaps resulting in reduced intake of leaf material. Positive responses to CP existed in some cases even though the plasma urea nitrogen (PUN) concentration in the blood of all heifers was not below 14 mg/dL and the IVDOM:CP of pasture samples collected in a manner to simulate diet selection by the heifers was below 6.5, both indicative of a situation where positive responses to CP are less likely. Hammond et al. (3) suggested that optimum range of PUN concentration for growing beef animals are from 8 to 10 mg/dL. Table 4. Nitrogen application rates effects on in vitro digestible organic matter (IVDOM), CP, and IVDOM:CP of leaf and stem fractions of limpograss pastures.x
x Data from da C. Lima et al. (2). Table 5. Average daily gain of yearling heifers grazing limpograss pastures in response to canopy height and CP supplementation, and limpograss pasture characteristics in response to canopy height.x
x Data from Newman et al. [9]. y BD = bulk density, kg of DM per ha/cm. z Orthogonal polynomial contrasts for the effect of canopy height on the response; L = linear, Q = quadratic, P < 0.01, NS = not significant, P > 0.10. Protein Supplementation for Cattle Grazing Limpograss Due to marginal CP relative to energy in limpograss pasture samples from the studies discussed above (11,12), subsequent studies evaluated protein supplementation as a means of improving the performance of cattle grazing limpograss pasture. In these studies, protein supplementation was achieved either through the feeding of various high-CP feedstuffs, incorporation of a legume into limpograss pasture, or through frequent N application rate of the limpograss pasture. Holderbaum et al. (4) used yearling steers (314 kg) to graze limpograss in a rotational stocking and either fed a corn-urea supplement at two levels of supplemental CP (supplements contained 210 or 500 g/kg CP and were fed at levels to provide a dietary CP concentration of 90 or 120 g/kg), or seeded aeschynomene (Aeschynomene americana L.) into the limpograss pasture. Providing supplemental CP in the form of corn-urea or aeschynomene increased steer ADG as compared to the unsupplemented control (Table 6). Steer ADG improved over the limpograss alone treatment with either supplement or legume in the pasture, regardless of the supplementation level, and there was no difference in ADG of steers supplemented with concentrate or grazing pastures overseeded with legumes. However, gain/ha was less for pastures overseeded with legume. PUN concentration of steers receiving no supplement averaged 6.0 mg/dL, indicative of low dietary CP relative to energy. Blood PUN concentration was increased from 8.2 to 11.4 mg/dL in cattle receiving 210 and 500 g/kg CP supplement, respectively. Also, TDN:CP ratios of greater than 8.5 in the limpograss pasture were suggestive of a potential positive response from protein supplementation (8). Overseeding aeschynomene into the limpograss pasture reduced the TDN:CP ratio below 7.0. Table 6. Average daily gain, gain per hectare, and PUN concentration of yearling steers grazing limpograss and fed protein supplements or grazing limpograss-aeschynomene (Aeschynomene americana) pastures and IVDOM, CP and IVDOM:CP of limpograss and limpograss-aeschynomene pastures.x
x Data from Holderbaum et al. (4). y Low CP = corn and urea formulated to 210 g/kg CP; estimated to provide a dietary CP of 90 g/kg High CP = corn and urea formulated to 500 g/kg CP; estimated to provide a dietary CP of 120 g/kg. z C = Control; L = Low CP; H = High CP; A = limpograss-aeschynomene pasture; Limpo = limpograss pasture; NS = not significant, P > 0.10. In North Florida, da C. Lima et al. (2) observed an interaction between N application rate of limpograss pasture and CP supplementation for ADG of yearling heifers (350 kg). In their studies, a factorial arrangement of treatments including N application rate (50 and 150 kg/ha) and CP supplement (none, corn-urea, corn-urea-undegradable protein) was utilized. The undegradable protein was a mixture of blood meal and corn gluten meal. Supplements were formulated to provide approximately 500 and 400 g/kg degradable intake protein, and 250 g/kg undegradable intake protein for the corn-urea-undegradable protein supplement. Heifers grazed limpograss pastures in a rotational stocking with a variable stocking rate used to add or remove animals in order to maintain a stubble height of 20 to 25 cm for all pastures at the end of a rotational stocking cycle. At the lower N application rate, the TDN:CP ratio of the limpograss forage was greater than 9.0 suggesting that an imbalance between CP and energy existed in the forage, and a positive response to CP supplementation was observed (Table 7). Also, PUN concentration in the blood of heifers grazing the low N application rate pastures and fed no supplement was very low (4.2 mg/dL), also indicative of low dietary CP relative to energy. At the low N application rate, heifers fed no CP supplement had decreased ADG and gain/ha. Both ADG and gain/ha were increased by feeding a CP supplement at the lower N application rate. At the higher N application rate, the TDN:CP of the limpograss forage was reduced compared to the lower N application rate, and was in the range where a response to protein supplementation would be less likely (8). Also, PUN concentration of heifers grazing the higher N application rate rate pastures and fed no supplement (9.2 mg/dL) was in the range where a response to CP supplementation might not be expected (3). Providing a CP supplement to heifers grazing limpograss pastures fertilized with 150 kg N per ha did not result in an increase in ADG or gain/ha. Table 7. Supplement by N rate interaction means for ADG and live weight gain/ha of yearling heifers grazing limpograss pastures and fed supplements varying in ruminal degradability, IVDOM, CP and IVDOM:CP of limpograss pasture fertilized at an N rate of 50 or 150 kg/ha.x
x Data from da C. Lima et al. (2). y BM = blood meal; CGM = corn gluten meal. z 50 and 150 refer to N application rate in kg/ha; C = control; U = urea supplement; UBC = urea + BM + CGM supplement. To investigate CP supplementation for cattle grazing limpograss in South Florida, Brown and Adjei (1) continuously stocked limpograss pastures using weaned steers (270 kg), which ensured that forage was available from early spring through late fall. Using this strategy, forage accumulated in the pastures during the summer for use in the fall. Molasses-based supplements containing no supplemental CP, urea, or urea plus feather meal were fed at the rate of 1.4 kg DM daily. In Years 1 and 2, large quantities of forage accumulated in the pastures, with large quantities of leaf material present in the upper portions of the canopy (Table 8). Forage samples obtained in a manner designed to simulate the grazing animal’s diet had IVDOM:CP ratios of 6.5 to 6.8, and PUN concentration in the blood of steers fed no CP supplement was high (10.6 to 12.4 mg/dL), both suggesting that a balance between CP and energy existed in the forage the cattle were consuming. Consistent with this, ADG was not influenced by CP supplementation in these years. A drought persisted during much of the trial in Year 3 and limpograss forage production was significantly reduced as compared to Years 1 and 2. Stem material made up a greater proportion of the upper layers of the canopy as compared to Years 1 and 2, leading to lower forage CP concentration and greater IVDOM:CP ratio in Year 3 as compared to Years 1 and 2. In Year 3, PUN concentration in the blood of steers fed no CP supplement was low suggesting an imbalance of dietary CP relative to energy. Subsequently, ADG was improved by the addition of supplemental CP from urea but was not further influenced by the addition of slowly degraded protein from feathermeal. Table 8. Average daily gain and PUN concentration of steers grazing limpograss pasture and fed molasses-based supplements containing urea and (or) hydrolyzed poultry feather meal, herbage mass, IVDOM, CP, and IVDOM:CP of limpograss pasture.x
x Data from Brown and Adjei (1). y Means in the same row followed by different letters are different (P < 0.05). Summary Limpograss is an attractive warm-season forage option for beef cattle producers in Florida because of its cool-season growth and reduced decline in TDN concentrations at late maturities. Grazing height, N fertilization, and supplementation are important management practices to improve performance of cattle grazing limpograss. Literature Cited 1. Brown, W. F., and Adjei, M. B. 2001. Urea and (or) feather meal supplementation for yearling steers grazing limpograss (Hemarthria altissima var. ‘Floralta’) pasture. J. Anim. Sci. 79:3170-3176. 2. da C. Lima, G. F., Sollenberger, L. E., Kunkle, W. E., Moore, J. E., and Hammond, A. C. 1999. Nitrogen application rate and supplementation effects on performance of beef heifers grazing limpograss. Crop Sci. 39:1853-1858. 3. Hammond, A. C., Kunkle, W. E., Bates, D.B., and Sollenberger, L. E. 1993. Use of blood urea nitrogen concentration to predict responses to protein or energy supplementation in grazing cattle. Pages 1989-1991 in: Proc. of the 17th Int. Grassl. Congr., Rockhampton, Australia. 8-21 Feb. 1993. Dunmore Press, Palmerston North, New Zealand. 4. Holderbaum, J. F., Sollenberger, L. E., Moore, J. E., Kunkle, W. E., Bates, D. B., and Hammond, A. C. 1991. Protein supplementation of steers grazing limpograss pasture. J. Prod. Agric. 4:437-441. 5. Kretschmer, A. E., Jr., and Snyder, G. H. 1979. Production and quality of limpograss for use in the subtropics. Agron. J. 71:37-43. 6. Minson, D. J. 1980. Nutritional differences between tropical and temperate pastures. Pages 143 in: Grazing Animals. F. H. W. Morley, ed. Elsevier Scientific, Amsterdam, The Netherlands. 7. Moore, J. E., Worrel, M. A., and Abrams, S. M. 1981. Quality of tropical perennial grass hays. Florida Res. Rept., Anim. Sci. Dep., Univ. of Florida, Gainesville, FL. 8. Moore, J. E., Kunkle, W. E., and Brown, W. F. 1991. Forage quality and the need for protein and energy supplements. Pages 113-123 in: Proc. of the 40th Annual Beef Cattle Short Course, Gainesville, FL. 1-3 May 1991. Anim. Sci. Dep., Univ. of Florida, Gainesville, FL. 9. Newman, Y. C., Sollenberger, L. E., Kunkle, W. E., and Chambliss, C. G. 2002. Canopy height and nitrogen supplementation effects on performance of heifers grazing limpograss. Agron. J. 94:1375-1380. 10. Pitman, W. D., Machen, R. V., and Pond, K. R. 1994. Grazing evaluation of Bigalta and Floralta limpograss. Crop Sci. 34:210-214. 11. Sollenberger, L. E., Ocumpaugh, W. R. Euclides, V. P. B., Moore, J. E., Quesenberry, K. H, and Jones Jr., C. S. 1988. Animal performance on continuously stocked ‘Pensacola’ bahiagrass and ‘Floralta’ limpograss pastures. J. Prod. Agric. 1:216-220. 12. Sollenberger, L. E., Rusland, G. A., Jones C. S., Jr., Albrecht, K. A., and Gieger, K. L. 1989. Animal and forage responses on rotationally grazed ‘Floralta’ limpograss and ‘Pensacola’ bahiagrass pastures. Agron. J. 81:760-764. |
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