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1.
Tall fescue (Festuca arundinacea Schreb.) infected with the endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) causes fescue toxicosis in cattle grazing the forage, but effects of the endophyte were considered to be abated soon after removal of the animals from pastures. Tasco-Forage, a proprietary extract from the brown seaweed Ascophyllum nodosum, is a known source of cytokinins and has increased antioxidant activity in both plants and the animals that graze the forage. Tasco was applied at 0 and 3.4 kg/ha to infected and uninfected tall fescue pastures in Virginia and Mississippi. Forty-eight steers grazed the pastures at each location during each of 2 yr (n = 192) before being transported to Texas for feedlot finishing. On arrival at the feedlot, steers from Tasco-treated pastures had higher (P < 0.01) monocyte phagocytic activity and tended (P < 0.07) to have higher major histocompatibility complex class II expression than steers that grazed the untreated pastures. A depression (P < 0.05) in monocyte immune cell function due to grazing infected fescue was detected throughout the feedlot finishing period but was reversed by Tasco. Rectal temperatures were elevated (P < 0.07) in steers that had grazed the infected tall fescue when they arrived in Texas, but by d 14 no difference was detected. However, by d 28 the temperature effects of infected tall fescue were reversed. Steers that had grazed infected fescue had lower (P < 0.01) rectal temperatures on d 112 of the feedlot period, demonstrating a much longer-lasting effect of the endophyte on thermoregulatory mechanisms than previously thought. Steers that had grazed Tasco-treated pastures had higher (P < 0.01) rectal temperatures on d 56 than steers that had grazed untreated fescue. Steers that had grazed the Tasco-treated pastures had higher marbling scores (P < 0.05) regardless of the endophyte, but no effect of Tasco or endophyte on gain was measured. Our data suggest that Tasco application to tall fescue pastures alleviated some of the negative effects of tall fescue toxicity.  相似文献   

2.
The objective of the current study was to delineate changes that occur in serum analytes and blood cellular elements in cattle that graze endophyte-infested (Neotyphodium coenophialum) tall fescue. Tall fescue is grown on more than 35 million acres (14.2 million ha) of pasture in the United States, and three-fourths of the pastures are infected with the endophyte at a 60% or greater level. Tall fescue toxicosis caused by endophyte-produced ergot alkaloids continues to be the most important grass-related disease in the United States, in terms of economic loss to animal producers. However, the agronomic attributes of tall fescue make it an attractive forage species because of its ability to withstand cool temperatures, drought, poor soil conditions, and intensive defoliation from herbivore species, including insects. Tall fescue toxicosis is a complex disease and the need exists to understand the mechanisms of the toxic effects in order to institute effective, prophylactic control measures. Our group previously reported changes that occur in serum biochemical analytes of cattle that graze endophyte-infected tall fescue. An additional year's worth of data have been added, strengthening and corroborating these data. Consistent and significant changes associated with tall fescue toxicosis during the 3-yr study included decreased serum concentrations of cholesterol, globulin (increased albumin/globulin ratio), prolactin, total protein, and copper. The activity of alanine aminotransferase was decreased in serum, whereas an increase in serum concentrations of creatinine and total bilirubin occurred. The present report also documents comparative hemograms of cattle that grazed endophyte-infected or endophyte-free tall fescue over a prolonged period. The mean erythrocyte counts were increased in cattle that grazed endophyte-infected tall fescue, whereas mean corpuscular hemoglobin and mean corpuscular volume were decreased, as were mean eosinophil counts. Thus, repeatable changes have been identified that occur in serum biochemical and blood cellular values of cattle grazing endophyte-infected tall fescue that will aid in understanding the pathogenesis of the disease. In addition, these consistently altered parameters can be used to assess the effectiveness of potential prophylactic treatments.  相似文献   

3.
Although endophyte-free tall fescue (Festuca arundinacea Schreb.) cultivars have been recognized as lacking persistence on droughty, infertile, sandy Coastal Plain soils, they have continued to be recommended for the more fertile and heavier bottomland soils in Louisiana. Two pasture experiments were conducted to assess animal performance on, and persistence of, endophyte-free genotypes on the fertile soil of central Louisiana. In the first experiment, performance of young, growing, crossbred beef cattle on AU-Triumph and Forager tall fescue pastures was compared with that on Marshall annual ryegrass (Lolium multiflorum Lam.) using put-and-take stocking over three growing seasons. In the second experiment, year-round stocking and stocking only in the cool season, with and without fall hay harvest, were compared with set-stocked AU-Triumph tall fescue pastures for 2 yr. Individual animal performance on annual ryegrass at 0.74 kg/d was greater than that on the two tall fescue cultivars, which averaged 0.57 kg/d and did not differ from each other. Although animal performance was affected by management of AU-Triumph tall fescue in the first year of grazing, responses in the second year did not differ. Only 2 or 3 yr of productive grazing were obtained from endophyte-free tall fescue in these experiments on central Louisiana clay loam soil. Disease damage from Rhizoctonia solani Kuehn. contributed to stand loss and appeared to hasten deterioration from summer stress and invasion by aggressive warm-season grasses. Results of these experiments and reports from other locations in Louisiana indicate that endophyte-free tall fescue is not sufficiently adapted for use as a pasture plant, even on the more productive Louisiana soils.  相似文献   

4.
The nonergot alkaloid-producing endo-phyte, AR542, has been shown to improve the persistence and yield of tall fescue pastures without causing the animal disorders commonly associated with tall fescue toxicosis. A 3-yr grazing study was conducted to compare effects of AR542-infected tall fescue pastures with wild type endophyte-infected (E+) tall fescue pastures on cow-calf performance. Replicated 7.3-ha pastures of each treatment were grazed by cow-calf pairs (16 pairs per pasture replication) each year from March to weaning in September. The cows were exposed to breeding on their respective pasture treatments from April 1 through June 15. The treatment groups were compared for reproductive performance, ADG, BCS, calf growth rate, and weaning weight. Blood samples were also collected for serum prolactin (PRL) analysis. There were no significant differences in calving rate (P = 0.98) or calving interval (P = 0.62) between pasture treatments. Cows that grazed the AR542 pastures subsequently gave birth to calves that were heavier (P < 0.05) than calves from cows that had grazed the E+ pastures. Cows grazing the AR542 pastures had higher (P < 0.05) BCS at the end of the grazing period, and had higher ADG during the grazing period. Calves raised on the AR542 pasture had higher (P < 0.05) ADG and weaning weights than calves of the same sex raised on the E+ pastures. Serum PRL concentrations were decreased (P < 0.05) in both cows and calves on the E+ pastures compared with serum PRL concentrations in cows and calves grazing the AR542 pastures. The results indicate that grazing tall fescue pastures infected with the AR542 endophyte may give significant advantages in cow-calf growth rates and BCS over grazing E+ pastures. However, there did not seem to be any benefit in reproductive performance in this trial. There was a small, but significant increase in birth weight in cows grazing AR542 pasture.  相似文献   

5.
The daily BW gain of stocker steers grazing tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort.]-based pastures typically declines during summer. To avoid these declines, in part to mitigate the effects of tall fescue toxicosis, it is commonly advised to move cattle to warm-season forage during this period. A 3-yr (2006, 2007, and 2008) grazing study was conducted to evaluate the effect of replacing 25% of the area of a tall fescue/clover (81% endophyte-infected) pasture system with "Ozark" bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with clover (Trifolium spp.) to provide summer grazing for stocker steers (TF+BERM). The TF+BERM treatment was compared with a grazing system in which tall fescue/clover (TF) pastures were the only type of forage available for grazing. Our objective was to determine if replacement of 25% of the land area in a fescue system with bermudagrass would increase annual beef production compared with a system based solely on tall fescue. The study was conducted at the Southwest Research and Education Center of the University of Missouri near Mt. Vernon. Each treatment was rotationally stocked with 5 steers (248 ± 19.3 kg) on 1.7 ha. Fertilizer applications were applied at rates recommended for each respective forage species. Total forage production, BW gain per hectare, and season-long ADG of steers was greater (P < 0.06) for TF+BERM than for TF in 2006, but none of these measures differed (P > 0.19) in 2007 or 2008. In vitro true digestibility of pastures was greater (P = 0.01) for TF (84.4%, SEM = 0.64%) compared with TF+BERM (80.6%, SEM = 0.79%), even in summer. The decreased in vitro true digestibility of the bermudagrass pastures likely negated any benefit that animals in TF+BERM had in avoiding the ergot-like alkaloids associated with endophyte-infected tall fescue. Renovating 25% of the pasture system to bermudagrass provided some benefit to the system in years when summertime precipitation was limited (2006) but provided no value in wetter years (2007 and 2008). Although renovating endophyte-infected tall fescue pastures to a warm-season forage is a widely used practice to mitigate tall fescue toxicosis, the benefits of this practice are limited if forage quality of the warm season component is poor.  相似文献   

6.
Cool-season grass mixtures are rarely evaluated for preference, yield, and persistence under horse grazing. The objectives of this research were to evaluate horse preference, forage yield, and persistence of cool-season grass mixtures under horse grazing. Eight commercially marketed and four experimental perennial cool-season grass mixtures were planted in 2009 in a randomized complete block with five replicates and grazed by four adult horses during 2010, 2011, and 2012. All mixtures contained four to six cool-season perennial grass species. Specie density measurements were taken in each spring and fall, and yield was mechanically measured before each grazing period. After grazing, preference was determined by visually assessing percentage of forage removal on a scale of 0 (no grazing) to 100 (100% of vegetation removed). Data were analyzed using a mixed-model analysis of variance and liner regression. Horses preferred mixtures containing tall fescue, perennial ryegrass, Kentucky bluegrass, and timothy (P < .001). Horses had less preference for mixtures containing ≥30% orchardgrass (P < .001). Mixtures had similar (P = .11) forage yields that ranged from 6,100 to 7,082 kg ha−1. After 2 years of grazing, orchardgrass and tall fescue increased; Kentucky bluegrass remained stable; and festulolium, meadow fescue, and perennial ryegrass had the greatest rate of decline in mixtures. Orchardgrass became the dominate species, regardless of initial percentage in the mixture. Mixtures containing tall fescue, perennial ryegrass, Kentucky bluegrass, and timothy should be planted in midwestern US horse pastures; however, mixtures will likely transition to tall fescue and Kentucky bluegrass–dominated pastures.  相似文献   

7.
Achieving economically optimum livestock production on rangelands can conflict with conservation strategies that require lower stocking rate to maintain wildlife habitat. Combining the spatial and temporal interaction of fire and grazing (pyric–herbivory) is a conservation-based approach to management that increases rangeland biodiversity by creating heterogeneous vegetation structure and composition. However, livestock production under pyric–herbivory has not been reported. In both mixed-grass prairie and tallgrass prairie, we compared livestock production in pastures with traditional fire and grazing management (continuous grazing, with periodic fire on tallgrass prairie and without fire on mixed-grass prairie) and conservation-based management (pyric–herbivory applied through patch burning) at a moderate stocking rate. Stocker cattle weight gain, calf weight gain, and cow body condition score did not differ (P > 0.05) between traditional and conservation-based management at the tallgrass prairie site for the duration of the 8-yr study. At the mixed-grass prairie site, stocker cattle gain did not differ in the first 4 yr, but stocker cattle gained more (P ≤ 0.05) on conservation-based management and remained 27% greater for the duration of the 11-yr study. Moreover, variation among years in cattle performance was less on pastures under conservation management. Traditional management in mixed-grass prairie did not include fire, the process that likely was associated with increased stocker cattle performance under conservation management. We conclude that pyric–herbivory is a conservation-based rangeland management strategy that returns fire to the landscape without reduced stocking rate, deferment, or rest.  相似文献   

8.
Native colonial and large ungulate herbivores infrequently coexist on contemporary landscapes but frequently would have in the past, and understanding these interactions is important for conservation in working landscapes—those lands managed for biological and economic objectives. Although many factors contribute to grassland bird declines, consistent and long-term removal of native herbivores from western grasslands promotes homogenous landscapes that are now uniformly grazed by cattle (Bos taurus). This shift in grassland disturbance patterns limits habitat availability for specialized grassland species. We investigated vegetation and bird community dynamics in pastures grazed by domestic cattle and a native colonial herbivore, the black-tailed prairie dog (Cynomys ludovicianus). The study occurred in the northern mixed-grass prairie of the United States on four experimental pastures stratified by the proportion of prairie dog occupancy to create an ecological gradient. Vegetation and bird surveys were conducted from 2012 to 2015 on and off prairie dog colonies. Vegetation and bird communities were not different along the experimental pasture gradient but did differ relative to location on versus off town. Prairie dogs induced changes in the plant community with midstatured grasses like side-oats grama (Bouteloua curtipendula) and green needlegrass (Nassella viridula) being associated with off-colony sites while on-colony sites were associated with disturbance-tolerant species such as fetid marigold (Dyssodia papposa). The bird community responded to changes in vegetation structure resulting from prairie dogs with grasshopper sparrows (Ammodramus savannarum) being more abundant off colonies in areas with greater vegetation structure, while bird species with more complex life histories, such as the upland sandpiper (Bartramia longicauda), were associated with both on ? and off ? prairie dog colonies. Our findings demonstrate the importance of maintaining spatial heterogeneity in working landscapes and show that native colonial herbivores can help achieve this in the presence of herbivory by domestic cattle.  相似文献   

9.
Awareness of herbivore diet composition is an essential element of rangeland stewardship. Objectives of our experiment were to characterize diet selection by yearling steers and mature ewes grazing native tallgrass prairie, changes in dietary preferences that occurred with advancing season, and overlap in selection patterns between ewes and steers. Eight contiguous native tallgrass pastures (31 ± 3.3 ha) were grazed by yearling beef steers (n = 279 per yr) from 15 April to 15 July for two grazing seasons. Mature ewes (n = 813 per yr) subsequently grazed four of the eight pastures (0.15 ha per ewe) from 1 August to 1 October each year. Beginning 1 May, five fresh fecal pats were collected along four permanent transects per pasture at 2-wk intervals until steers were removed on 15 July. Subsequently, fecal grab samples were collected from 25 designated ewes per pasture on 15 August and 15 September. Microhistological analyses were conducted on fecal samples to estimate dietary botanical composition, using 17 grass, forb, and browse species from the experimental site as reference standards. Botanical composition of pastures was estimated annually in October. Diet selection was evaluated using Kulcyznski’s Similarity Index. The proportions of total graminoids and total forbs in steer diets were not different (P = 0.37) among sampling periods. Steer diets were dominated by graminoids (≥ 88.4% of diets) throughout the experiment. Steers and ewes exhibited strong preference for Bouteloua gracilis, Buchloe dactyloides, Dalea purpurea, and Liatris punctata. Ewes also demonstrated strong preferences for Vernonia baldwinii and Ambrosia artemisiifolia. Steers avoided Lespedeza cuneata and Symphyotrichum ericoides, whereas ewes did not avoid any of the reference standards. Ewes selected approximately equal proportions of graminoids and forbs (58% and 42% of diets, respectively), and proportions did not differ (P = 0.67) between sampling periods. Diet selection by mature ewes and yearling steers overlapped by 65% under the conditions of our experiment.  相似文献   

10.
Defoliation aimed at introduced cool-season grasses, which uses similar resources of native grasses, could substantially reduce their competitiveness and improve the quality of the northern tallgrass prairie. The objective was to evaluate the use of early season clipping and fire in conjunction with simulated increased levels of atmospheric nitrogen deposition on foliar canopy cover of tallgrass prairie vegetation. This study was conducted from 2009 to 2012 at two locations in eastern South Dakota. Small plots arranged in a split-plot treatment design were randomized in four complete blocks on a warm-season grass interseeded and a native prairie site in east-central South Dakota. The whole plot consisted of seven treatments: annual clip, biennial clip, triennial clip, annual fire, biennial fire, triennial fire, and undefoliated control. The clip plots consisted of weekly clipping in May to simulate heavy grazing. Fire was applied in late April or early May. The subplot consisted of nitrogen applied at 0 or 15 kg N · ha?1 in early June. All treatments were initially applied in 2009. Biennial and triennial treatments were reapplied in 2011 and 2012, respectively. Canopy cover of species/major plant functional groups was estimated in late August/early September. Annual clipping was just as effective as annual fire in increasing native warm-season grass and decreasing introduced cool-season grass cover. Annual defoliation resulted in greater native warm-season grass cover, less introduced cool-season grass cover, and less native cool-season grass cover than biennial or triennial defoliation applications. Low levels of nitrogen did not affect native warm-season grass or introduced cool-season cover for any of the defoliation treatments, but it increased introduced cool-season grass cover in the undefoliated control at the native prairie site. This study supports the hypothesis that appropriately applied management results in consistent desired outcomes regardless of increased simulated atmospheric nitrogen depositions.  相似文献   

11.
Spring application of a plant growth regulator, mefluidide, to tall fescue (Festuca arundinacea Schreb.) pastures grazed from May to September reduced (P less than .05) available DM and digestible OM per hectare by 51 and 41%, respectively, compared to untreated pastures. However, seasonal averages for N, Ca and P content and in vitro OM disappearance (OMD) were greater (P less than .05) and NDF was lower (P less than .05) in tall fescue from mefluidide-treated pastures than in untreated pastures. Compared to hand-clipped samples, esophageal extrusa of tall fescue was 63% higher (P less than .05) in N (2.7 vs 1.7%) and 26% lower (P less than .05) in NDF (52.6 vs 69.9%) than hand-clipped tall fescue samples, regardless of treatment. Extrusa and hand-clipped herbage samples were similar (P greater than .10) in OMD during May and September, but OMD of extrusa was greater (P less than .05) during June, July and August compared to clipped samples. As a consequence of preventing stem elongation and seedhead formation earlier in the growing season, mefluidide treatment of tall fescue maintained forage quality at a higher level during midsummer.  相似文献   

12.
The majority of native prairie has been lost throughout North America. Much of the remaining prairie is used for livestock grazing, so conservation of prairie species depends on sustainable grazing practices. Our objective was to evaluate the benefits of twice-over rotational grazing, in comparison with continuous season-long grazing and ungrazed “idle” fields, in conserving prairie songbirds. Northern mixed-grass prairie in southwest Manitoba, Canada is near the northern range limits for many endangered grassland birds, and thus is an important area for evaluating the contribution of twice-over grazing in the conservation of songbirds, including species at risk. In 2008 and 2009, we compared the relative abundances and diversity of grassland birds on 22 twice-over rotation, 15 season-long, and 8 ungrazed sites, using multiple 100-m fixed-radius point-count plots per site. Analyses were conducted using generalized linear mixed models. Although one obligate grassland bird, Savannah sparrows (Passerculus sandwichensis), had significantly higher relative abundances on twice-over than season-long sites in 2009, season-long pastures had higher species richness and diversity of obligate grassland birds in both years. Season-long grazing may actually benefit grassland bird communities by creating spatially heterogeneous but temporally stable areas of high and low livestock use within the pasture, thus increasing diversity of microhabitats. We found little evidence that twice-over grazing contributed to the conservation of grassland songbirds in subhumid northern mixed-grass prairies.  相似文献   

13.
Tasco-Forage is an Ascophyllum nodosum seaweed-based product that has increased antioxidant activity in both plants and animals. Endophyte (Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and uninfected tall fescue (Festuca arundinacea Schreb.) pastures in Virginia and Mississippi during 1997 were treated or not with 3.4 kg Tasco/ha in April and July. There were two replications of each treatment at each location. Forty-eight steers (6/replication) grazed pastures at each location (n = 96) from April to October prior to transportation to Texas Tech, Lubbock, for finishing during a 160-d period in the feedlot. Blood (antemortem) and liver (postmortem) samples were collected. After slaughter and chilling, the left strip loins (IMPS #180) were collected from three randomly selected steers from within each pasture replication (n = 48). Strip loins were vacuum-packaged and stored at 2 degrees C. At postmortem d 7, 14, 21, and 28, strip loins were removed from packaging and fabricated into 2.54-cm steaks. Following each fabrication day postmortem, the strip loins were repackaged and stored at 2 degrees C until the following postmortem time. After the prescribed fabrication, steaks were overwrapped with polyvinyl chloride film, subjected to simulated retail display at 2 degrees C for up to 3 d, and subjective and objective color were evaluated daily by a trained panel. Steaks from Mississippi steers that had grazed Tasco-treated fescue retained higher (P < 0.05) CIE a* color scores throughout retail display. Steaks were more uniform and had less discoloration and less browning (P < 0.05) if they were from steers that had grazed Tasco-treated fescue, and the effect was greatest for steers from Mississippi (location x Tasco interaction; P < 0.05). The endophyte in tall fescue may decrease uniformity and increase lean discoloration and two-toning of beef steaks when removed from vacuum packaging on or beyond d 21 postmortem (endophyte x Tasco x postmortem day interaction: P < 0.05). Vitamin E in liver was increased (P < 0.06) and serum vitamin E was decreased (P < 0.09) in steers that had grazed the treated pastures. These experiments indicated that Tasco applied to tall fescue during the grazing season can improve color stability and extend beef shelf-life, particularly in cattle grazing infected tall fescue. The mode of action of Tasco is not clear, but antioxidants and specific vitamins may be involved.  相似文献   

14.
Nonergot alkaloid-producing endophytes from New Zealand were inserted into tall fescue (Festuca arundinacea) cultivars in an attempt to address the problem of fescue toxicosis in grazing sheep. A 3-yr grazing study was conducted to determine lamb performance and to evaluate toxicosis in lambs grazing nonergot alkaloid-producing endophyte-infected (AR542 or AR502), endophyte-free (E-), or wild-type toxic endophyte-infected (E+) Jesup tall fescue or nonergot alkaloid-producing endophyte-infected (AR542) Georgia-5 tall fescue. Replicated 0.11-ha tall fescue paddocks were established at the central Georgia Branch Station during September 1997 and stocked with lambs from spring 1998 through autumn 2000. Mean ergot alkaloid concentrations were higher (P < 0.01) in E+ forage than in AR542, AR502, and E- tall fescue, and ergot alkaloid concentrations in E- plants and plants infected with AR542 and AR502 were low. Forage availability did not differ (P = 0.92) across treatments during autumn and was higher (P < 0.05) in Georgia-5 AR542 than in Jesup AR502 and E+ pastures. Initial serum prolactin (PRL) concentrations did not differ (P = 0.58) across treatments during autumn, but were higher on Jesup AR542 than E+ during spring. Post-treatment serum PRL concentrations were depressed (P < 0.01) on E+ compared with AR542, AR502, and E- in both spring and autumn. Signs of heat stress were observed in E+ lambs during periods of high ambient temperatures. Mean post-treatment rectal temperature and mean stocking rate exhibited treatment x year interactions (P < 0.05). Lamb ADG was higher (P < 0.05) on AR542, AR502, and E- than on E+ tall fescue. Similarly, gain/hectare was higher (P < 0.015) on AR542, AR502, and E- than on E+. Tall fescue pastures containing AR542 and AR502 endophytes yielded lamb performance that did not differ from that on E- tall fescue and which was superior to performance on E+ tall fescue. Depressed PRL concentrations and elevated rectal temperatures as indicators of toxicosis were evident only in lambs grazing E+ tall fescue, suggesting that nonergot alkaloid-producing endophyte-infected tall fescue is a viable alternative for alleviating tall fescue toxicosis.  相似文献   

15.
We postulate that phosphorus (P) fertilization may increase above-ground net primary productivity (ANPP) of rotationally grazed rangelands without reducing the legume component, as does N fertilization. In doing so, we evaluated the effect of phosphate fertilization on the production and relative contribution of legumes and grasses of native and old tall fescue (Festuca arundinacea Schreb) grasslands; we recorded annual production, seasonal productivity, and biomass contribution of each component. The experiment was conducted in a commercial farm located in the Flooding Pampa and managed under rotational grazing. Treatments consisted of two fertilization programs (66 (P66) and 29 (P29) kg P · ha-1 supplied as rock phosphate and/or monoammonium phosphate from 1997 to 1999) and a nonfertilized control. A paddock dominated by native grassland and another dominated by old tall fescue grassland were selected. Nine 5-ha plots were established in each paddock, and treatments were randomly assigned. During the experimental period, from October 1998 to October 1999, total above-ground biomass was harvested from each plot before and after each grazing period and separated into components: tall fescue, other C3 perennial grasses, legumes, C3 annual grasses, C4 grasses, forbs, and standing dead material. ANPP of each component was estimated during the warm (October 1998–February 1999) and the cool (March 1999–September 1999) season. In native grassland, phosphate fertilization increased ANPP of C3 annual grasses and legumes during both the warm and the cool seasons; therefore annual ANPP of the grassland under P66 was 40% higher than under P29 and doubled ANPP of nonfertilized plots. Phosphate fertilization didn't increase total annual ANPP of old tall fescue grassland, but it did increase ANPP of legumes during both seasons.  相似文献   

16.
Knowledge of how tallgrass prairie vegetation responds to fire in the late growing season is relatively sparse and is based upon studies that are either spatially or temporally limited. To gain a more robust perspective of vegetation response to summer burning and to determine if repeated summer fire can drive vegetational changes in native tallgrass prairie, we evaluated species cover and richness over a 14-yr period on different topographic positions from ungrazed watersheds that were burned biennially in the growing season. We found that annual forbs were the primary beneficiaries of summer burning, but their fluctuations varied inconsistently among years. Concomitantly, species richness and diversity increased significantly with summer burning but remained stable through time with annual spring burning. After 14 yr, species richness was 28% higher in prairie that was burned in the summer than in prairie burned in the spring. Canopy cover of big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans [L.] Nash) increased significantly over time with both summer and spring burning, whereas heath aster (Symphyotrichum ericoides [L.] Nesom), aromatic aster (Symphyotrichum oblongifolium [Nutt.] Nesom), and sedges (Carex spp.) increased in response to only summer burning. Kentucky bluegrass (Poa pratensis L.) cover declined in both spring-burned and summer-burned watersheds. Repeated burning in either spring or summer did not reduce the cover or frequency of any woody species. Most perennial species were neutral in their reaction to summer fire, but a few species responded with large and inconsistent temporal fluctuations that overwhelmed any clear patterns of change. Although summer burning did not preferentially encourage spring-flowering forbs or suppress dominance of the warm-season grasses, it is a potentially useful tool to increase community heterogeneity in ungrazed prairie.  相似文献   

17.
Data from 403 calves from Angus, Brahman, and reciprocal-cross cows sired by Polled Hereford bulls were used to evaluate the impact of postweaning backgrounding forages on postweaning BW, gains, and carcass traits. Calves were born (spring of 1991 through 1994) and reared on either endophyte-infected tall fescue or common bermudagrass pastures. After weaning, calves were transported 360 km to the Grazinglands Research Laboratory, west of El Reno, OK, and, within breed and preweaning forage, were assigned to one of the following winter stocker treatments: 1) winter wheat pasture or 2) dormant native prairie plus supplemental CP. In March, winter stocker treatments were ended and calves were grazed as a single group on cool-season grasses until early July (1992, 1993, and 1994) or late May (1995), when the feedlot phase began. In the feedlot, calves were fed a high concentrate diet for an average of 120 d until a backfat thickness of > 10 mm was reached. Calves were shipped in truck load lots to Amarillo, TX (350 km), for processing and collection of carcass data. Averaged over calf breed group, calves wintered on wheat pasture gained faster (P < 0.01) during the stocker phase (0.71 vs 0.43 kg); had heavier (P < 0.01) final feedlot weights (535 vs 512 kg); lower feedlot (P < 0.01) ADG (1.37 vs 1.53 kg); heavier (P < 0.01) carcass weights (337 vs 315 kg); larger (P < 0.01) longissimus muscle (84.9 vs 81.8 cm2); higher percentage (P < 0.01) of kidney, heart, and pelvic fat (2.32 vs 2.26); and higher (P < 0.01) dressing percentage (62.2 vs 61.3) than calves backgrounded on native prairie. Maternal heterosis for stocker ADG was evident in calves backgrounded on native prairie but not on winter wheat (P < 0.10), but the two environments were similar in maternal heterosis for feedlot ADG and carcass traits. Calves wintered on native prairie were restricted in growth and expressed compensatory gain during the feedlot phase but not during the spring stocker phase. Dormant native grasses can be used to winter stocker calves excess to the winter wheat pasture needs, but ownership of these calves would have to be retained through the feedlot phase to realize any advantage of built-in compensatory gain. Finally, these data suggest that expression of maternal heterosis for weight gain is more likely in calves backgrounded on native prairie than in calves grazed on winter wheat.  相似文献   

18.
草坪蒸散量及水分管理的研究   总被引：24，自引：5，他引：19  
孙强  韩建国  姜丽  李鹏 《草地学报》2004,12(1):51-56
对高羊茅、草地早熟禾、野牛草和结缕草的蒸散量以及水分管理的研究表明:在生长季节4种草坪水分蒸散规律均为"双峰型",5月和8月是2个高峰期;高羊茅2001年总蒸散量为831.28mm,2002年849.33mm,较草地早熟禾(734.51mm和764.37mm)高11.5%;野牛草和结缕草差异不显著,分别为609.82mm和612.10mm;冷季型和暖季型草坪的总蒸散量差异显著(P＜0.05),其中高羊茅＞草地早熟禾＞野牛草=结缕草;4种草坪草夏季日蒸散量均处于较低水平;生长季需要补充的灌溉水在2001年高羊茅为621.34mm,草地早熟禾为543.88mm;2002年高羊茅为536.85mm,草地早熟禾466.13mm,野牛草332.16mm,结缕草326.65mm;降水量的年际波动造成2年的灌溉需水量差异较大.  相似文献   

19.
The objective of this study was to compare an introduced warm-season perennial grass (plains bluestem, Bothriochloa ischaemum) to native tallgrass prairie for cow-calf production. Three systems were used, two based on tallgrass prairie with two different forms of protein supplementation and one based on plains bluestem as the primary forage. The systems were as follows: 1) native tallgrass prairie with pelleted oilseed meal as the winter protein supplement (native-control); 2) native tallgrass prairie with limited access to wheat pasture as the winter protein supplement (native-wheat); and 3) plains bluestem with limited access to wheat pasture as the protein supplement (bluestem-wheat). Oilseed meal protein supplements were fed twice weekly. Cows grazing wheat pasture were allowed 6 h of grazing twice weekly. Ninety-nine cows per year were used over the 3-yr study. Cows were sired by either Charolais, Gelbvieh, Angus, or Hereford bulls out of commercial Angus-Hereford dams. Calves were sired by Simmental bulls. Calving and weaning rate increased over time but did not differ among systems or breed types. System did not influence the size or body condition score of cows or the performance of calves, but changes in the weight and condition scores of cows were greater on either native system than on the bluestem-wheat system. Cows from Charolais and Gelbvieh bulls were taller (P < 0.05), and heavier (P < 0.05), and weaned heavier (P < 0.05) calves than cows from Angus or Hereford bulls. The weight of cows on the bluestem-wheat system tended to decrease over time, whereas cows grazing on the native systems tended to gain weight over time. The native-control system was the most profitable system based on cow production. If excess hay produced from the bluestem-wheat system was sold as a cash crop, then this system was the most profitable. In general, we conclude that limit-grazing wheat pasture is a viable alternative to oilseed meal as protein supplement for wintering dry cows. Although the bluestem system had 2.5 times the carrying capacity of the native prairie systems, increased productivity was offset by increased production costs. All systems were equal on a cow basis for providing nutrients for the cow-calf production system.  相似文献   

20.
The objective of this study was to compare methane emission by goats consuming the condensed tannin-containing forage sericea lespedeza (Les-pedeza cuneata) or a mixture of crabgrass (Digitaria ischaemum) and Kentucky 31 tall fescue (Festuca arundinacea). Two groups of 12 Angora does (initial average BW = 41.5 +/- 2.7 kg) that previously grazed a pasture of sericea lespedeza or crabgrass/tall fescue for approximately 4 mo were used. After 1 wk of adaptation to metabolism cages, gas exchange was measured for 24 h in an open-circuit respiration calorimetry system with four head boxes. Forage harvested daily from the previously grazed pastures was consumed ad libitum. Crude protein concentration was 10.3 and 13.0%, IVDMD was 64.5 and 75.3%, and the level of condensed tannins was 17.7 and 0.5% for sericea lespedeza and crabgrass/tall fescue, respectively. Dry matter intake (1.11 vs. 0.67 kg/d) and digestible DMI (estimated from IVDMD; 0.71 vs. 0.51 kg/d) were greater (P < 0.01) for sericea lespedeza than for crabgrass/tall fescue. Ruminal ammonia N (3.7 and 9.9 mg/dL; P < 0.001) and plasma urea-N concentrations (16.7 and 20.9 mg/dL; P = 0.07) were lower for sericea lespedeza than for crabgrass/tall fescue. Concentrations of individual and total VFA and the acetate-to-propionate ratio in ruminal fluid did not differ between treatments (P > 0.19). Despite higher DMI by goats fed sericea lespedeza, daily energy expenditure (409 vs. 431 kJ/kg BW(0.75)), heart rate (70 vs. 73 beats/min), and the ratio of energy expenditure to heart rate (5.82 vs. 5.94) did not differ between sericea lespedeza and crabgrass/tall fescue, respectively (P > 0.13). Methane emission expressed as both quantity per day or relative to DMI was lower (P <0.001) for sericea lespedeza than for crabgrass/tall fescue (7.4 vs. 10.6 g/d and 6.9 vs. 16.2 g/kg DMI). Substantial differences between the forages in condensed tannins concentration and methane emission by Angora goats suggest that condensed tannins decreased methane emission.  相似文献   

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