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FORAGE & GRAZINGLANDS

Effects of Storage Conditions on the Forage Quality Characteristics and Ergovaline Content of Endophyte-Infected Tall Fescue Hays

^a Dep. of Animal Science, Univ. of Arkansas, Fayetteville, AR 72701
^b USDA-ARS, US Dairy Forage Research Center, Univ. of Wisconsin Marshfield Agric. Exp. Stn., 8396 Yellowstone Dr., Marshfield, WI 54449
^c Univ. of Arkansas Livestock and Forestry Branch Stn., 70 Experiment Station Dr., Batesville, AR 72501
^d Dep. of Crop, Soil, and Environmental Sciences, Univ. of Arkansas, Fayetteville, AR 72701. Contribution of the Arkansas Agric. Exp. Stn. This project was funded in part by USDA Cooperative Agreement #58-6227-8-040

^* Corresponding author (coblentz{at}wisc.edu).

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Throughout the southern Ozark Highlands, endophyte-infected tall fescue [Lolium arundinaceum (Schreb.) Darbysh] hay often is stored outdoors, without cover. At two research sites (Fayetteville and Batesville, AR), the effects of unprotected storage were assessed for large round bales of tall fescue hay packaged at three diameters (1.1, 1.4, and 1.7 m). Bales were stored over winter either inside or outside on wooden pallets and then sampled at three depths (0–0.15 m, 0.15–0.31 m, and 0.31–0.46 m). At both locations, bale diameter had no effect (p > 0.05) on dry matter (DM) recovery or nutritive value. Generally, there was little deterioration of nutritive value during the storage period, regardless of treatment; however, some interactions (p 0.041) of storage location and sampling depth were observed at each experimental site. Ruminal disappearance kinetics of DM exhibited some statistical differences (p 0.030) in response to treatment; however, their relative magnitude was generally small, and there was little evidence to suggest biological relevance. After storage, concentrations of ergovaline were not affected (p > 0.05) by baling treatment at Batesville (overall mean 256 µg kg^–1); however, this was a 27.3% reduction from the initial concentration immediately after mowing. At Fayetteville this reduction was even greater, falling by 79.4% between standing forage (539 µg kg^–1) and samples taken from baled hay after storage (111 µg kg^–1). At both sites, bales stored outside on wooden pallets exhibited relatively small changes in nutritive value, disappearance kinetics, and ergovaline at the bale surface relative to the internal portions of the bale.

Abbreviations: ADF, acid-detergent fiber • CP, crude protein • DM, dry matter • IVDMD, in vitro dry matter disappearance • NDF, neutral-detergent fiber

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
THROUGHOUT THE OZARK Highlands, tall fescue [Lolium arundinaceum (Schreb.) Darbysh] hay is packaged most frequently in large round bales and stored outdoors without structural cover. Several studies (Anderson et al., 1981; Collins et al., 1987, 1995; Russell et al., 1990) have evaluated storage losses and changes in nutritive value for forage crops packaged in round bales tied or wrapped with various techniques and stored under different conditions. Most of these efforts (Anderson et al., 1981; Collins et al., 1987; Russell et al., 1990) have been concentrated on alfalfa (Medicago sativa L.) or alfalfa/grass hay mixtures, and associated evaluations of nutritive value have been limited to relatively routine assays such as neutral-detergent fiber (NDF), acid-detergent fiber (ADF), crude protein (CP), and in vitro dry matter disappearance (IVDMD). Only minimal information is available on ruminal kinetics of dry matter (DM) disappearance from tall fescue hays (Humphry et al., 2002; Turner et al., 2004), or on concentrations of toxins produced by the fungal endophyte throughout the haying or ensiling processes (Turner et al., 1993; Roberts et al., 2002).

Most of the tall fescue hay produced throughout this region is infected with the fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon, & Hamlin comb. nov. (Glenn et al., 1996). This endophytic association often improves growth characteristics and persistence of tall fescue plants (Siegel et al., 1985; Hill et al., 1991; West et al., 1993; Malinowski and Belesky, 2000), especially under stressful growing conditions. Many factors can contribute to this stressful growing environment; this includes southern Ozark pasture soils, which are shallow and often acidic and have poor water-holding capacity with relatively low fertility (Sauer et al., 1998). While the association of the fungal endophyte with tall fescue may improve persistence and growth, toxins produced by this fungus also diminish livestock performance (Read and Camp, 1986; Peters et al., 1992; Schmidt and Osborn, 1993; Paterson et al., 1995). A somewhat dated estimate suggests that these problems cost livestock producers in the USA, and especially those in southeastern states, an estimated $609 million annually (Hoveland, 1993).

Ergovaline is used frequently as an indicator of potential fescue toxicosis in livestock; however, other ergopeptine and lysergic acid derivatives also may contribute to this problem. Although scientists continue to debate (i) which of these derivatives are specifically responsible for fescue toxicosis, (ii) their possible mode(s) of action (Hill, 2005), and (iii) the most appropriate methodologies for quantitative analysis, the negative effects of these toxins on livestock performance are understood widely by producers. Garner et al. (1993) has suggested that ergovaline and other ergot alkaloids found commonly within endophyte-infected tall fescue are not stable during exposure to air and light. Work by Roberts et al. (2002) suggests that concentrations of toxins may decline in response to various forms of environmental exposure associated with the haying and ensiling processes. Therefore, it is possible that the combined processes of haying and storage may act to reduce toxin loads in tall fescue hays and also may serve as a simple management tool to further reduce the effects of fescue toxicosis throughout the region. Most studies have not attempted concomitant evaluations of storage characteristics, changes in nutritive value, and ruminal DM disappearance kinetics, while also monitoring concentrations of ergovaline or total ergot alkaloids. Our objectives were to assess the effects of bale diameter, storage location, and sampling depth on changes in endophyte-infected tall fescue hay exposed to ambient climatic conditions over winter at two experimental sites in northern Arkansas.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Fayetteville Study
Experimental Site
A well-established 2.8-ha stand of endophyte-infected ‘Kentucky 31’ tall fescue located at the University of Arkansas Agricultural Experiment Station in Fayetteville (36°05' N; 94°10' W) was chosen for the study. The soil type was primarily a Nixa cherty silt loam (loamy-skeletal, siliceous, mesic Typic Fraiudults) with 3 to 8% slopes. Before initiating the hay study, the site was fertilized with ammonium nitrate (34–0–0) at a rate of 56 kg N ha^–1 on 9 Apr. 2004. Species composition was determined by the modified step-point method (Owensby, 1973) on 31 May 2004, when tall fescue plants had reached the soft-dough stage of growth. The species composition of the experimental site immediately before mowing (31 May 2004) was 84.7% tall fescue, 8.0% bermudagrass [Cynodon dactylon (L.) Pers.], 2.7% annual ryegrass (Lolium multiflorum Lam.), 1.3% Kentucky bluegrass (Poa pratensis L.), 1.3% johnsongrass [Sorghum halepense (L.) Pers.], 0.7% dallisgrass (Paspalum dilatatum Poir.), 0.7% orchardgrass (Dactylis glomerata L.), and 0.6% cheat (Bromus tectorum L.).

Sampling Procedures before Mowing
Before mowing, the entire experimental site was divided into three experimental blocks, primarily on the basis of soil topography (slope). Approximately 120 tillers (40 per block) were sampled immediately before mowing to evaluate the percentage of endophyte infection in tall fescue plants. Tillers were collected by walking each experimental block in a zig-zag pattern and clipping tillers as close to the crown as possible with hand shears. Tillers were immediately placed in unsealed plastic freezer bags within an ice-filled cooler, transferred to a refrigerator (4°C) within 30 min of collection, and then analyzed for percentage of endophytic infection by an immunoblot procedure (Gwinn et al., 1992). The infection level of tall fescue tillers was 73 ± 9.5%.

In addition, each field block also was walked in a similar zig-zag pattern, and random tall fescue plants were clipped to a 7.6-cm stubble height to determine concentrations of ergovaline in the standing forage. After collection, tall fescue samples were sealed immediately in plastic freezer bags, submerged in ice in an insulated cooler, and then transported to an ultralow temperature freezer (–80°C), where they were stored pending analysis for ergovaline.

Baling Procedures
At 1300 h on 1 June, adjacent swaths were inverted and raked together with a New Holland Model 258 side-delivery rake and then packaged immediately into round bales bound with net wrap using a Model XL604 baler (Vermeer Manufacturing Co., Pella, IA). Bales were made at three preset diameters (1.11, 1.35, and 1.59 m (Table 1); designated as small, medium, and large, respectively) by utilizing electronic bale monitoring equipment mounted within the cab of the tractor. A total of 18 bales were made, which included two of each diameter from each field block (total of six bales per block). Within each field block, bales of the three different diameters were created in random order, which was varied for each subsequent block. All bales were tied with two revolutions of plastic net wrap and weighed immediately with a hanging digital scale (AME- TEK Test and Calibration instruments, Kew Gardens, NY) that was fastened to the front-end loader attachment of a tractor. Bale width and diameter were determined with a tape measure, thereby allowing the calculation of bale volume and DM density.

Bale Storage
For each field block, one of the two small-, medium-, and large-diameter bales was selected randomly for inside storage, while the remaining bale of each diameter was stored outside. Bales stored outside were placed on wooden pallets located on a dense bermudagrass sod with full exposure to natural sunlight and precipitation. Pallets were placed approximately 2 m apart to allow air and light to penetrate to the soil surface. Bales designated for inside storage also were placed on wooden pallets positioned approximately 2 m apart, but these wooden pallets were situated on a concrete floor within an unheated pole barn. The pole barn had no side walls, but nonexperimental bales were stacked around the perimeter of the barn, thereby providing the experimental bales positioned on the floor within the interior of the barn some protection from the ambient weather conditions. This arrangement exposed experimental bales stored inside to similar temperatures and humidities as those stored outside, but eliminated exposure to both direct sunlight and precipitation.

Poststorage Sampling and Evaluation
On 8 Feb. 2005, all bales were measured for width and diameter and weighed a second time. Recoveries of DM for each bale were calculated based on differences in DM weights before and after storage. Unlike the sampling protocol for bales before storage, poststorage core samples were taken at three depths: (i) 0 to 0.15 m (surface); (ii) 0.15 to 0.30 m (middle); and (iii) 0.30 to 0.46 m (deep). This procedure was used to assess the effects of weathering at various depths within each hay bale. Bales were sampled in a uniformly spaced pattern of 36 total probes that were located over the entire half of the bale surface area opposite that from which the initial samples taken during June 2004. To prevent contamination, the 36 core samples were taken first at the 0 to 0.15-m depth, and then at the 0.15 to 0.31-m depth by extracting deeper samples from the same holes. Finally, the 0.31 to 0.46-m depth was sampled by extracting even deeper samples from the existing 36 probe holes. A total of approximately 250 g of sample was composited from the 36 sample cores taken from each layer of each bale. Following thorough mixing, a 75-g subsample was transferred to a plastic freezer bag, submerged in ice in an insulated cooler, and then stored (–80°C) as described previously for subsequent evaluation for ergovaline. The remainder of each sample (175 g) was dried to constant weight under forced air (50°C) to determine the concentration of DM within each bale layer, and then retained for evaluation of nutritive value and in situ disappearance kinetics of DM.

Batesville Study
Experimental Site
A companion study was conducted simultaneously at the Livestock and Forestry Branch Station, located near Batesville, AR (35°50' N, 91°48' W). A well-established 1.6-ha stand of endophyte-infected ‘Kentucky-31’ tall fescue grown on a Peridge silt loam soil (fine-silty, mixed, mesic Typic Paleudalfs) with 3 to 8% slopes was fertilized with urea (46–0–0) at a rate of 56 kg N ha^–1 on 23 Feb. 2004. Tiller samples (60 tillers) uniformly spaced over the entire experimental site were collected and evaluated for percentage of endophyte infection (Gwinn et al., 1992), as described for the Fayetteville study; at the time of harvest, the percentage of infection at the Batesville site was 80%. Forage was allowed to accumulate without grazing or clipping until it was harvested on 12 July 2004; at this time, tall fescue plants had reached the mature seed stage of growth. The initial concentration of ergovaline in tall fescue forage (at mowing) was obtained in a similar manner to that described for the Fayetteville study, except that tillers were collected from windrows by a technician immediately after mowing, rather than by clipping with hand shears before mowing. The harvest date and associated maturity differences between the Fayetteville and Batesville sites were largely related to weather conditions at Batesville. Although the total cumulative rainfall at Batesville for June 2004 was only 56% of the 30-yr average (Table 2), weather conditions were not especially stable. There were at least two rainfall events during each individual week of the 6-wk period beginning on 30 May and continuing through 10 July. Garner et al. (1993) has suggested that ergovaline is water soluble and subject to leaching from forage plants; therefore, exposure to precipitation might be expected to reduce concentrations within wilting hays. Because one of the objectives of the study was to document potential changes in concentrations of ergovaline as a result of haying and storage, we felt it was essential that hay be baled without rain damage, and at a moisture concentration (<100 g kg^–1) likely to prevent spontaneous heating. Therefore, meeting these requirements was given a higher priority than any potential confounding between sites created by maturity or age differences.

In Situ Procedures
Selection of Hays
Excessive sample numbers prohibited the evaluation of kinetics of ruminal DM disappearance for all possible combinations of experimental site, bale diameter, storage location, sampling depth, and replication (bale). To reduce the number of hays to a manageable number (15–20) for this type of analysis, two procedural compromises were necessary. First, bale diameter generally had little effect on characteristics of nutritive value; therefore, small and large bales were eliminated completely from the in situ portion of the study. Second, within each experimental site, core samples from medium-diameter bales with common treatment effects (storage location and sampling depth) were composited over like bales before conducting kinetic evaluations. For example, the composite hay sample representing the surface layer of hay stored outside at Fayetteville was composed of equal proportions of the core samples obtained from the surface layers of the three medium-diameter bales stored outside at that experimental site. Similarly, two prestorage composite hay samples were created as positive controls for both experimental sites from medium-diameter bales designated for either inside or outside storage. A total of 16 composite hays were evaluated. These included four prestorage controls (one from both inside and outside bales at both experimental sites), six poststorage hays from Fayetteville (surface, middle, and deep layers of bales stored both inside and outside), and the six corresponding poststorage hays from Batesville.

Animal Care
Five 795 ± 54.7-kg ruminally cannulated crossbred (Gelbvieh x Angus x Brangus) steers were used for the in situ incubations. Cannulations and care of the steers were approved by the University of Arkansas Animal Care and Use Committee (Protocol #05005). Steers were housed in individual 3.4- x 4.9-m pens with concrete floors that were cleaned regularly and offered a diet of orchardgrass hay (162 g kg^–1 CP, 513 g kg^–1 NDF, and 287 g kg^–1 ADF) and a cracked corn–based supplement (920 g kg^–1 cracked corn, 33 g kg^–1 molasses, 30 g kg^–1 limestone, and 17 g kg^–1 trace mineral salt). On an as-fed basis, the basal diet contained 900 g kg^–1 orchardgrass hay and 100 g kg^–1 supplement. The diet was offered in equal portions at 0630 and 1430 h for a maintenance level of intake (1.8% of bodyweight) daily. Fresh water was offered continuously on an ad libitum basis, and steers were adapted to the basal diet for 10 d before initiating the trial.

Kinetic Procedures
In situ procedures were consistent with the standardized techniques described by Vanzant et al. (1998). Five-gram samples of each forage were weighed into dacron bags (10 cm x 20 cm; 50 ± 10-µm pore size; ANKOM Technology, Corp.) that were heat sealed with an impulse sealer (Type TISH-200; TEWI International Co., Ltd., Taipei, Taiwan). Before insertion into the rumen, all dacron bags were placed in 35- x 50-cm mesh bags and incubated in tepid water (39°C) for 20 min. Samples were then suspended in the ventral rumen immediately before the 0630-h feeding and incubated for 3, 6, 9, 12, 24, 36, 48, 72, or 96 h. Upon removal from the rumen, bags were rinsed immediately in a top-loading washing machine (model LXR7144EQ1; Whirlpool Corp., Benton Harbor, MI). Rinsing procedures included 10 cold-water rinse cycles (47 L of water), where each cycle consisted of 1 min of agitation and 2 min of spin (Coblentz et al., 1997; Vanzant et al., 1998). A separate set of bags was preincubated as described previously (39°C) and rinsed without ruminal incubation (0 h). After rinsing, the sample residues were dried to a constant weight at 50°C and equilibrated with the atmosphere before determination of residual DM (Vanzant et al., 1996).

The percentage of DM remaining at each incubation time was fitted to the nonlinear regression model of Mertens and Loften (1980) using PROC NLIN of SAS (1990). Forage DM was partitioned into three fractions based on relative susceptibility to ruminal disappearance. The A fraction was defined as the immediately soluble portion, although it also may include some minute insoluble particles that may wash out of dacron bags (Coblentz et al., 1998; Galdámez-Cabrera et al., 2003). Fraction B represented the portion of DM that disappeared at a measurable rate; and Fraction C was defined as the portion of DM that was undegraded in the rumen. Fractions B and C, disappearance rate, and the discrete lag time were determined directly by the nonlinear regression model. For each forage, Fraction A was calculated as 1000 – (B + C), and the effective ruminal disappearance of DM was calculated as (A + B)[K_d/(K_d + K_p)] (Ørskov and McDonald, 1979), where K_d is the disappearance rate and K_p is the passage rate. Ruminal passage rate (0.018 ± 0.0024 h^–1) of the basal diet was determined for each steer using acid-detergent-insoluble ash as an internal passage marker (Waldo et al., 1972).

Experimental Design
Bale Measurements and Nutritive Value
Whole-bale measurements for the Fayetteville study, including prestorage evaluation of nutritive value, were analyzed as a randomized complete block design with three field replications. Treatments were arranged as a 3 x 2 factorial that included three bale diameters (small, medium, or large) and two storage locations (inside or outside). Prestorage and poststorage data were analyzed independently using PROC GLM of SAS (1990). The companion trial conducted at Batesville was analyzed similarly, except the six factorial treatment combinations were analyzed as a completely randomized design with unbalanced replication across treatments. The nutritive value and concentrations of ergovaline for poststorage samples from both studies were analyzed at the whole-plot level as described above, but a subplot factor (sampling depth) was added to create a split-plot design. Whole-plot treatment factors (bale diameter, storage location), and their associated interaction were tested for significance with the bale diameter x storage location x block interaction for Fayetteville and the replication (bale diameter x storage location) interaction for Batesville. Sampling depth and all higher-order interactions were tested with the residual error mean square. For bale diameter and storage location, means were separated by the PDIFF option of SAS (1990). Sampling-depth means were compared with two orthogonal contrasts: (i) surface versus middle and deep layers and (ii) middle versus deep layer.

In Situ Disappearance Kinetics of Dry Matter
Disappearance kinetics of DM for 16 composite hay samples representing both experimental sites, two storage locations, and three sampling depths, as well as the associated prestorage positive controls, were evaluated as a randomized complete block design with the five steers designated as blocks. Within experimental site, single degree-of-freedom orthogonal contrasts (PROC GLM of SAS Institute [1990]) were utilized to evaluate effects of treatment. Significance was declared for all response variables at p = 0.05, unless otherwise specified.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Prestorage Bale Characteristics
At both sites, hay was very dry at baling; the overall mean DM was 888 and 953 g kg^–1 at Fayetteville (Table 1) and Batesville (Table 3), respectively. Little respiration and subsequent spontaneous heating occurs in hays packaged at concentrations of DM > 850 g kg^–1 (Rotz and Muck, 1994). This was verified at the Fayetteville site by means of thermocouple wires inserted into the surface and core of each bale; maximum and average bale temperatures over the entire storage period for the 18 bales at that location were 42.0 ± 3.17 and 25.3 ± 1.87°C, respectively. The small SEM associated with initial bale diameter (0.015 and 0.018 m for Fayetteville and Batesville, respectively) indicates that bale monitoring equipment was used effectively by operators at both sites to randomly create bales of three different diameters. Differences (p < 0.05) in bale diameter created intentionally as part of the treatment structure resulted in predictable differences (p < 0.05) in bale volume, and initial wet and dry weights among small, medium, and large-diameter bales at both locations. However, none of these interrelated factors affected (p > 0.05) the DM density of bales at either site (overall means 168 and 129 kg m^–3 at Fayetteville and Batesville, respectively).

Precipitation
Total precipitation at Fayetteville from June 2004 through March 2005 exceeded the 30-yr average by 86 mm (Table 2); however, cumulative precipitation for individual months varied sharply from normal. Precipitation exceeded the 30-yr average by at least 33 mm during June, July, October, and November 2004, as well as January and February 2005, but was at least 51 mm below normal during August, September, and December 2004. Similarly, total precipitation at Batesville over this same period was 63 mm above normal, but totals for individual months also varied widely. This included 221 and 216 mm in October and November 2004, respectively, but only 1 mm for September 2004.

Poststorage Bale Characteristics
Fayetteville
After storage, bale diameter had no effect (p > 0.05) on concentrations of DM within the surface, middle, or core layers, or on recovery of DM (Table 4). Storage location (inside or outside) affected several bale characteristics on the final evaluation date. Most importantly, concentrations of DM in the bale surface layer were markedly lower (95 g kg^–1; p < 0.05) for bales stored outside compared to those stored inside. This response also was observed for the middle layer, but the magnitude of the difference was small (10 g kg^–1; p < 0.05), and hay remained dry (overall mean 900 g kg^–1) regardless of storage location. No difference (p > 0.05) in concentrations of DM was observed between storage locations for samples obtained from the deep layer of the bale. Bales stored outside exhibited a 16-kg greater (p < 0.05) final wet weight than those stored inside, which likely can be explained on the basis of differences in moisture retention, primarily at the bale surface. Despite the wetter nature of the surface layer for bales stored outside, there were no differences (p > 0.05) in recovery of DM across storage locations (overall mean 936 g kg^–1). Bales stored outside exhibited little visual evidence of a weathered layer and likely benefited greatly from storage on wooden pallets that separated bales from the soil surface, thereby preventing any wicking action of moisture from the soil surface into the bale.

For bales stored outside at Batesville, concentrations of CP (p < 0.001), ADF (p = 0.003), cellulose (p = 0.048), lignin (p < 0.001), and whole-plant ash (p < 0.001) differed at the bale surface relative to the interior bale layers (Table 7). There was a sharper contrast for some response variables than observed at the Fayetteville site; specifically, CP, lignin, and whole-plant ash exhibited differentials of 11, 17.1, and 7.0 g kg^–1. These sharper contrasts were consistent with evidence of increased water retention relative to the Fayetteville site. Overall, responses from both research sites are consistent with other work. Several studies (Anderson et al., 1981; Collins et al., 1987, 1995; Russell et al., 1990) have reported either statistically significant or numerically greater concentrations of fiber components within the weathered surface layer compared to the internal portion of the bale. While generally less consistent, similar trends have been observed for CP (Anderson et al., 1981; Collins et al., 1995). Presumably, these responses are caused by the leaching of highly digestible water-soluble components from the forage, the respiratory activity of microorganisms at the bale surface, or both. Each of these processes should act to concentrate water-insoluble fiber components by removing water-soluble compounds, such as plant sugars. Surprisingly, there was no difference (p > 0.05) between bale layers for NDF at Batesville, and the differential (p = 0.003) between surface and interior layers for ADF was small (12 g kg^–1); while this seems somewhat in contrast with the sharper responses for lignin and whole-plant ash, which also should increase by these same indirect mechanisms, it also is possible that some actual loss of fiber components occurred under the moist environment at the bale surface (Rotz and Muck, 1994).

Ruminal Disappearance Kinetics of Dry Matter
Fayetteville
The kinetics of ruminal DM disappearance for hays harvested and stored at Fayetteville (Table 8) were consistent with previous kinetic estimates for tall fescue hays (Humphry et al., 2002), and with the limited evidence of moisture retention, DM loss, and biologically meaningful changes in forage nutritive value described previously. Although some responses to treatment were statistically significant, their relative magnitude was generally small, and there was little evidence to suggest biological relevance. Fraction A, which is immediately soluble, was greater for hays immediately after baling than for all stored bales (p = 0.001), but the actual differential was small (12 g kg^–1). An even smaller differential (8 g kg^–1; p = 0.004) was observed for contrasts of bales stored inside versus those stored outside. In both cases, an inverse relation was observed for Fraction B; greater proportions of the total plant DM were partitioned within this fraction for stored hays compared to bales sampled before storage (p = 0.001), and for bales stored inside compared to those stored outside (p = 0.001). However, these changes also were minor (14 and 11 g kg^–1, respectively). Fraction B also was greater (p = 0.030) within the middle and deep layers compared to the surface for bales stored inside, but this difference also was very small (10 g kg^–1). There were no responses (p > 0.05) to treatment for Fraction C (overall mean = 279 g kg^–1), lag time (1.20 h), and disappearance rate (0.037 h^–1). It is likely that Fraction C, the proportion of plant DM unavailable in the rumen, would be a relatively sensitive indicator of deterioration, and the lack of response to treatment is further indication of chemically stable hay at all bale layers. The effective disappearance of DM from bales sampled immediately after baling was greater (p = 0.030) than observed for all hays sampled after storage, but this response also was small (8 g kg^–1), further indicating stability in the hay over time.

Ergovaline
At the time tall fescue forages were mowed, the concentrations of ergovaline were 539 ± 162.1 and 352 ± 61.6 µg kg^–1 at the Fayetteville and Batesville locations, respectively. After storage at Fayetteville, no treatment factor or interaction of treatment factors affected (p > 0.05) concentrations of ergovaline, except for sampling depth (p = 0.003). Within this context, samples taken from the surface layer exhibited greater (p = 0.001) final concentrations of ergovaline (167 vs. 83 µg kg^–1) than did the interior bale layers (Table 10). At Batesville, no treatment factor affected (p > 0.05) concentrations of ergovaline after storage (overall mean = 256 µg kg^–1), again indicating there were limited effects of exposure. Reasons for these responses are unclear. Garner et al. (1993) has suggested that ergovaline is water soluble and subject to leaching from forage plants; therefore, exposure to precipitation and weathering might be expected to reduce concentrations within stored hays. Furthermore, Kallenbach et al. (2003) has shown that concentrations of ergovaline decline in response to weathering during late winter within standing stockpiled forages.

	CONCLUSIONS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
These results show that the surface layer of large round bales of tall fescue will exhibit minimal deterioration when bales are packaged at relatively high densities, tied with net wrap, and elevated off the ground during an extended storage period. Although not compared directly, bales tied with twine and stored outside under similar conditions exhibited more retention of moisture, greater DM loss, and more negative changes in nutritive value within the surface layer. A follow-up study is needed to document storage characteristics for bales stored on the ground compared to those elevated, bales tied with net wrap compared to sisal twine, and for any possible interaction of these factors. The relatively minor changes at the surface layer for bales tied and stored outside relative to interior bale layers suggests that producers could substantially improve the quality of their stored forages with simple management techniques. Monitoring of ergovaline suggests that the toxicity of the surface layer is not reduced substantially during a 9-mo storage period, but that ergovaline is reduced substantially over the haymaking and storage processes.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Received for publication October 12, 2006.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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