Journal of the NACAA
Volume 12, Issue 1 - June, 2019
Summer Stockpiling: A Systems Approach to Extending Grazing
- Benner, J. K., Extension Agent, Virginia Cooperative Extension
Booher, M.R., Extension Agent, Virginia Cooperative Extension
Clark, R.A. , Extension Agent, Virginia Cooperative Extension
Fiske, D., Superintendent, Shenandoah Valley AREC/McCormick Farm, Virginia Cooperative Extension
Summer stockpiling is a management practice that foregoes mechanized harvest and defers grazing on selected cool season forages from spring green up to early August. Although some plant growth matures and becomes unpalatable, accumulated vegetative growth provides a significant amount of digestible dry matter for late summer grazing. This accumulated growth can be grazed intensively to increase utilization efficiency and grazing days. Remaining cool season pastures can be stockpiled for winter grazing, further extending the grazing season. In this study and demonstration, we considered the potential economic value of the summer stockpile and examined the value of nitrogen fertilization for increasing forage supply and nutritive value. Low rates of nitrogen fertilization (50 lb/ac) in May did not return significant grazing or nutritional benefits, but did raise ergot alkaloid levels. However, when successively combined with fall stockpiling, summer stockpiling provided an average extra 46 days of grazing and reduced hay feeding costs by as much as $51/cow. Summer stockpiling offers opportunity to significantly improve profitability of livestock production systems.
Hay and feed costs are consistently the largest expense for beef cattle operations (Miller, et al., 2001; Groover and Eberly, 2011). In Virginia, efforts to extend the grazing season often include fall stockpiling tall fescue. A cool season grass, tall fescue (Lolium arundinaceum) grows on over one million acres in Virginia (Hall et al., 2009) largely due to its persistence in the face of droughts, floods, insects and pathogens, limited fertility, and less-than-ideal grazing management.
These characteristics owe largely to the presence of a fungal endophyte infecting most of the fescue that grows in Virginia and through the upper South’s “fescue belt”. While the endophyte benefits the plant, it also produces toxic ergot alkaloids that negatively affect livestock performance. Effects of alkaloid consumption are most visible in summer, causing “summer slump” or “summer syndrome” that is associated with high levels of heat stress and low forage intake.
Despite this limitation, tall fescue (particularly ‘KY-31’) lends itself to fall stockpiling for winter grazing. Fall stockpiling tall fescue has long been a recommended practice for Virginia beef producers. This practice extends the grazing season by providing “stockpiled” grass forage for winter grazing, reducing winter hay and feeding costs. Among cool season forages, tall fescue is perhaps the best at maintaining its quality through winter. Furthermore, alkaloid concentration decreases with repeated frosts (Kallenbach, et al, 2003).
Summer stockpiling is a relatively new management practice. Similar to fall stockpiling, both grazing and mechanized harvest are deferred from April until August. The accumulated forage is then grazed intensively while pastures designated for fall stockpiling are allowed to grow (from August to November). Anecdotal evidence indicates summer stockpiling reduces hay production needs, hay-feeding days and total feed costs. This management is most successful in combination with intensive grazing practices, which improve forage utilization efficiency and improve profitability (White and Wolf, 2009). Because endophyte-infected tall fescue is the primary forage in Virginia, it will be important to understand how deferred grazing and management inputs such as fertility affect forage nutritive value and alkaloid levels.
To investigate the practicality of summer stockpiling, a two-year non-replicated study was conducted. The study evaluated the effect of strip grazing summer stockpiled fescue on extending the grazing season and reducing winter feed costs with two fertility treatments. Additional responses of interest included forage yield, nutritive value and ergot alkaloid concentrations. For comparison, costs and nutritional values of hay were recorded. We also sought to determine if field measures for nutritive value and alkaloid concentrations were similar to measures selected by a grazing animal. In the year following the conclusion of the non-replicated study; five on farm demonstrations were held with local producers to further evaluate the application of the practice. These demonstrations involved working with producers on an individual basis to gauge their perception and implementation of the practice.
Materials and Methods
Non-Replicated Field Trial
The non-replicated field trial was conducted at the Shenandoah Valley Agricultural Research and Extension Center/McCormick Farm (Shenandoah Valley AREC, SVAREC) in Raphine, Virginia. Treatment plots were selected from a series of eight, 2-acre paddocks established on a Frederick-Caneyville Complex soil (USDA Web Soil Survey, 2015). These eight paddocks comprised a self-contained grazing system, allowing two paddocks (25% of total acreage) to be reserved for summer stockpile while six paddocks were rotationally grazed from May to mid-July (75% of total acreage, Figure 1). Grazing was then concentrated on 4 paddocks to prepare for fall stockpiling, allowing two additional paddocks to rest (Figure 2). The two summer stockpiled paddocks were then grazed beginning in August at the same time that half the acreage (8 acres; 4 paddocks) was fertilized and reserved for winter stockpiling (Figure 3). Treatments were rotated among plots from year to year to ensure all paddocks received similar management over time. With 8 paddocks, this translates to summer stockpile occurring on the same two paddocks only once every four years.
The following series of figures describe each step of the summer stockpiling grazing system.
Figure 1. Green-up through July. Two paddocks were summer stockpiled. The remaining acreage (75% of the total) was dedicated to rotational grazing. Eight fall calving cows were grazed a week in each paddock before the group was moved. Care was taken to leave a 4-5 inch residual in each paddock after grazing. The rotational grazed acreage yielded around 77+ days of grazing.
Figure 2. Mid-July to mid-August. Summer stockpiled paddocks continued to accumulate growth. An additional two paddocks were rested. Grazing was concentrated on the ground for the fall stockpile or 50% of the total acreage (30+days of grazing).
Figure 3. Mid-August to mid-October. Summer stockpiled growth was strip grazed from August to October (50+ days of grazing). In good years, the rested paddocks can be grazed one final time before strip grazing the fall stockpile.
The potential impact of nitrogen fertilizer on summer stockpile yield was measured on one paddock by a application of 50 lbs N/acre as urea. In both years, treatment 1, the control treatment, did not receive any nitrogen fertilizer. In both years, treatment 2 received 50 lbs N/acre in late May. Aggregate pasture composition score for the eight paddock area was assessed by visual appraisal in year 1 on 5/28/2015. The visual appraisal was assessed at 10 locations throughout each paddock and averaged to be 57.5% fescue, 5.5% orchardgrass, 37% bluegrass. For thistle control, both plots were spot mowed with a bush hog only in high thistle areas on 7/27/2015 at the height setting of 18-20 inches. This procedure was not needed in year 2. Otherwise, forage growth was left undisturbed and stockpiled until 8/19 in year 1 and 8/18 in year 2.
Pasture clipping samples were taken to determine total pasture nutrient content, pasture yield and alkaloid toxicity using a pasture quadrat, as depicted in Figure 4. Each sample area enclosed by the quadrat was cut to a height of 3 inches above the soil surface and collected for analysis. The stockpile itself was strip grazed by 8 fall calving cow calf pairs in both years of the study, with the majority of the cows calving while grazing the summer stockpile.
To evaluate actual animal selection of forage ergot alkaloids and nutrient concentrations, one esophageal fistulated Hereford steer was fasted in a dry lot for 12 hours before being permitted to graze the plots successively. The steer was then fitted with the fistula (Bar Diamond, Inc., Parma, ID.) and 1 quart plastic bag for sample collection (Figure 5). During data collection, the steer was permitted to graze 45 minutes to 1 hour in each plot or in a time frame that produced 4-6 samples. Samples were immediately chilled to preserve integrity of ergots within plant tissue and shipped on ice to Agrinostics, LTD, Watkinsville, GA. Nutrient analysis was conducted by Cumberland Valley Analytical Services, Waynesboro, PA.
Figure 4. Pasture quadrat sample.
Figure 5. Hereford steer with fistula and sample bag.
In the year following the conclusion of the trial, five separate on-farm demonstrations were conducted in Augusta, Page, Shenandoah and Clarke Counties. The objective of these demonstrations was to show producers the value of summer stockpiling to extend the grazing season and reduce feed costs. Two of the demonstrations (Augusta and Page) collected grazing and stock density data. Stock density was calculated using Animal Unit Months (AUM) as described by Pratt & Rasmussen (2001). All five collected nutrient concentration and yield data.
At the Augusta demonstration site a producer summer stockpiled an 8.8 acre field from April till August 1, 2017. Animals used to graze the stockpile were 26 heifers. A portable water source and backfence were employed to split the pasture into thirds of approximately 2.9 acres to increase grazing efficiency. This was compared to an 11 acre field that was cut for hay and then grazed after a recovery period. Total costs of hay and summer stockpiled grazing were compared.
A 19 acre field was summer stockpiled from April 1 to August 14, 2017. Animals used to harvest the stockpile were 41 cow calf pairs. For the first two weeks of grazing the cattle were allowed access to the adjacent field for shade. The summer stockpiled field was strip grazed with fence being moved every three days. Total costs of hay and summer stockpiled grazing were compared.
Shenandoah and Clarke Counties
Yield and forage quality were measured at demonstration sites in Shenandoah and Clarke Counties.
Results and Discussion
Yield, stock density and grazing days are shown in Table 1. At SVAREC in year 1 (2015) cows began strip grazing in the summer stockpile on 8/19/2015 and concluded on 10/26/2015. Fall stockpiled grazing began on 10/26/2015 and ended on 1/19/2016. In year 2 (2016) cows began strip grazing the summer-stockpiled paddocks on 8/18/2016 and concluded on 10/10/2016. Due to favorable environmental conditions, the pairs were able to strip graze an additional 30 days (Oct. 10 – Nov. 10) on the two paddocks that were pulled out of the grazing rotation and rested. Strip grazing on the fall stockpile began on 11/10/2016 and concluded on 1/12/2017. Together, summer and fall stockpiling netted a total of 153 days in year 1 and 116 days in year 2 for an average of 134 days. The summer stockpile averaged a length of 60 days over the two years.
At the Augusta demonstration heifers began grazing the summer stockpile on 8/1/2017 in the first 3 acres before being moved to the second 3 acres on 8/5/2017 and the last 3 on 8/12/2017. The heifers were removed from the field on 8/21/2017. The summer stockpiled field was then rested until cattle were moved to the field to be wintered in November.
The cow-calf pairs began grazing the Page County site on 8/14/2017 and finished grazing on 9/28/2017. Cattle were allotted grass to move fence every 3 days.
Table 1. Yield, stock density and grazing days, 2015-2017.
|Year||Location||Treatment||Yield DM lbs/acre||Stock Density (AUM/acre)||Summer Stockpile Grazing Days||Fall Stockpile Grazing Days|
|2017||Shenandoah A||0 N||5702|
|2017||Shenandoah B||0 N||2773|
The forage species at the demonstration sites were mainly cool season grasses. The Page site had some red clover present while the Clarke site had some Johnsongrasss. Each site excluded cattle from the summer stockpile beginning on April 1 with the exception of Augusta and Shenandoah B which removed cattle from the stockpile in mid-April and mid-May, respectively. Nutrient concentrations for both years of the study and demonstration sites are show in Table 2. This table includes total sward samples collected using the quadrat and samples collected from the fistulated steer. For comparison, Table 3 presents hay analysis from the research station and the Augusta site.
Table 2. Summer stockpile average nutrient concentrations. CP=crude protein; TDN=total digestible nutrients.
|2017||Shenandoah A||0 N||8.8||55.0|
|2017||Shenandoah B||0 N||14.2||59.0|
Table 3. Hay average nutrient concentrations.
|2015||SVAREC Hay||0 N||8.5||54.3|
|2015||SVAREC Hay||50 N||8.5||54|
|2017||Augusta Hay||0 N||11.7||58.4|
Our chief objective with this study was to evaluate the positive impact on feed costs by implementing summer stockpiling into a grazing system. We determined summer stockpiling costs and hay costs at the Shenandoah Valley AREC. An opportunity cost of $50/acre and assumption of a 2.5 ton/acre yield was used to assess the loss of value of forgoing grazing the summer stockpile from April until August. Costs of labor of strip grazing and related supplies are included in the calculation.
Table 4. SVAREC summer stockpile costs.
|0 N/acre||0 N/ton||50 N/acre||50 N/ton|
|Fertilizer application 50 lb/acre||$0||$0||$30||$9.18|
|Opportunity cost of not grazing earlier||$50||$14.01||$50||$15.30|
|Cost of feeding supplemental hay||$0||$0||$0||$0|
|Cost per cow per day (30 lbs dry matter/day)||$0.34||$0.51|
Hay costs for SVAREC are presented in Table 5. Hay ground is typically grazed 30+ days after mowing. Total costs include labor for harvest and feeding. The research station is consistently stocked at a rate of 2.6 pasture and hay acres per cow. Hay production costs for each demonstration were calculated using farm records and VCE hay production budgets (Groover and Eberly, 2007).
Table 5. SVAREC hay production costs.
|Per Acre||Per ton|
|Lime pro-rate 3 years||$10||$4|
|Machinery fixed costs||$36.46||$14.58|
|Cost per cow per day (30 lbs dry matter/day)||$1.73|
The above calculations put summer stockpile grazing savings at $1.39/cow/day over feeding hay, compared to the 0 N/acre treatment (Table 4).
The Augusta farm also recorded summer stockpile and hay costs. An opportunity cost of $40/acre was assessed for deferring grazing until August. Costs of the stockpile were greater than at SVAREC, likely due to a lower stockpile yield and lower utilization. However, costs were still $0.97/head/day below corresponding hay feeding costs.
Table 6. Augusta summer stockpile costs and hay costs.
|Summer Stockpile||Per acre||Per ton||Hay||Per acre||Per ton|
|Fertilizer application 50 lb/acre||$0||$0||Fertilizer||$103.60||$56.00|
|Opportunity cost of not grazing earlier||$40||$24.88||Lime||$10.00||$5.41|
|Costs of feeding supplemental hay||$0.00||$0.00||Fuel harvest||$19.37||$10.47|
|Total cost||$90.00||$55.99||Labor feeding||$20.00||$10.81|
|Cost per cow per day (30 lbs dry matter/day)||$0.84||Machinery fixed costs||$28.63||
|Cost per cow per day (30 lbs DM/day)||$1.81|
At the Page demonstration (Table 7), the cooperating farmer estimated that if he had baled hay and then grazed briefly in mid-summer and then fall stockpiled the field, that one 19 acre field would have provided 75 days' worth of feed to that herd of cattle. When the farmer used the field for summer stockpile it provided 45 days of grazing. The farmer wanted to calculate an additional 30 days of hay feeding to his cost to equitably compare it to his normal system. Thus, hay feeding costs of 30 days were added to the costs of grazing the summer stockpile for 45 days for a total of 75 days. Hay production costs were calculated assuming the same acreage as used for the summer stockpile.
Table 7. Page demonstration summer stockpiling and hay production costs.
|Summer Stockpile and Supplemental Hay Costs||Total Hay Production Costs|
|Total hay needs (assume 800 lb. rolls)||46||Total cost to mow, rake and bale||$1520|
|Hay cost per bale||$40||Total cost to move hay to storage||$300|
|Hay feeding cost per day||$50||Total cost to feed hay (per day cost*days hay will last)||$2,939.20|
|Total cost of summer stockpile||$971.43||Total cost of additional N||$532|
|Total hay cost||$1,845||Labor to move cattle when grazing||$218.57|
|Total hay feeding cost||$1,500|
|Total cost||$4,316.43||Total cost||$5,506.77|
|Total days cattle are fed||75||Total days cattle are fed||75|
|Total costs per acre||$227.18||Total cost per acre||$289.83|
|Total costs per ton||$114.74||Total cost per ton||$146.38|
|Estimated cost per day||$55.55||Estimated cost per day||$72.72|
|Estimated cost per cow per day||$1.40||Estimated cost per cow per day||$1.77|
Yield across both years of the trial, including both nitrogen treatments, and the demonstration sites ranged from 2273 to 8850 and averaged 5444 dry matter lbs/acre. Applying nitrogen in May did not appear to increase the final yield of the summer stockpile at the research station. The authors theorize that if summer stockpile were attempted on a field with a lower fertility status status, a spring nitrogen application may improve yield or quality, or both. The Clarke site yield may have been negatively impacted by poor soil fertility as it had a high amount of Johnsongrass. The Shenandoah B and the Augusta sites likely had lower yields due to both having been a winter feeding area with cattle not removed until after April 1. Year to year differences were seen at the research station with stockpile yield and grazing days greater in year 1 than year 2.
Cool season grasses often enter a semi-dormant stage in late summer, increasing rest time needed between grazing intervals. Spring flush growth has reached full maturity by late summer and is of low quality and palatability. To accomplish optimal forage utilization, high density strip grazing is recommended.
Though not as lush as spring forage growth, summer stockpiled grasses are comparable to first cutting hay. As shown in table 8, %TDN averaged 56.1% across both years of the trial and five demonstration sites while crude protein % averaged 10.8%. These figures meet the crude protein needs of a cow in early lactation and 94% of the TDN requirement (National Research Council, 2000). Thus, it is likely that with some animal foraging selectivity, summer stockpiling will meet the needs of fall calving cows without additional supplementation. It is important to note that with strip grazing selectivity goes down and dietary intake of energy is decreased. Nevertheless, strip grazing is still the preferred method of grazing summer stockpile to increase utilization of the forage.
Table 8 also shows the nutrient sample from the esophogeally fistualed steer. Interestingly, the steer did appear to favor forage with high ergot alkaloid content. In both years and in both treatments clipped samples were nominally lower than fistula obtained samples. The steer also selected similar ergot content across both the 0 N treatment and the 50 N treatment. This could explained by the steer selecting more green and vegetative growth.
Table 8. Animal selectivity while grazing the summer stockpile.
|0 N (ppb ergots)||384||972.1|
|50 N (ppb ergots)||715.5||860|
Ergot Alkaloids and Fescue Toxicity
Ergot alkaloid samples revealed a range of ergot concentrations. At SVAREC, average total ergot alkaloids measured 851.8 ppb in 0 N treatement samples, and 1050.4 ppb in 50 N treatment samples. This increase was expected, due to the nitrogen application in May. Total ergot alkaoids were measured in the study. There is a question as to whether ergovaline, an alkaloid thought to be the primary cause of fescue toxicity may be a more direct measure of potential toxicity of fescue than total ergot alkaoids (Rodgers et al., 2011). Although the majority of samples collected were around 400 ppb total ergot alkaloids, the percentage that were ergovaline was not evaluated. Further work is needed to quanity potential toxicity of summer stockpiled fescue, and to determine the effect of timing of nitrogen application on ergot alkaloid concentratration.
Total Grazing Days and Cost Savings
Total savings per cow per year of grazing the summer stockpile for SVAREC, Augusta and Page are presented in Table 9. Each of these scenarios demonstrate the cost savings of grazing the summer stockpile versus making hay and feeding hay from the same acreage. Lower stocking densities and yield, as was the case at the Augusta site, will reduce potential savings. Likewise, purchasing hay to make up for lower productivity on the Page demonstration site will reduce potential savings. If hay is needed from the potential summer stockpiled field, producers should consider purchasing hay or reducing cattle numbers to limit hay production expense.
Table 9. Annual summer stockpile grazing days and savings per cow.
|SVAREC Year 1||SVAREC Year 2||Augusta||Page||Average|
Perhaps most significantly, summer stockpiling has helped the Center reserve a larger amount of acreage for fall stockpiling. Combined, summer and fall stockpiling averaged 139 days of grazing stockpiled forage over the two year study. This systems approach to grazing allows the Shenandoah Valley Agricultural Research and Extension Center routinely graze in excess of 250 days each year.
Many livestock operations face difficulty stockpiling acreage for fall and winter grazing, especially in a dry summer or a fall after a hay cutting. Furthermore, many of these same operations face difficulty in making hay in the proper maturity stage for high quality. Operations that routinely cut hay in the early spring only to feed it out again in early fall should consider adoption of summer stockpiling into their grazing system to expand fall stockpiled acreage. Our study and demonstration work show summer stockpiling can be a realistic alternative and more cost effective practice than making hay for fall or early winter feeding. Our findings show that summer stockpile nutrient content, especially that selected by a grazing animal, is equal or of greater value than many grass hays, making it an even more attractive option.
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Groover, G., and Eberly, E. (2007). Stockpiled Fescue Pasture with Spring Hay Cutting. 2007 Virginia Farm Business Management Crop Budgets. Virginia Cooperative Extension Publication 446-048. Accessed at https://pubs.ext.vt.edu/446/446-047/446-047.html.
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Rodgers, W.M., Roberts, C.A., Andrae, J.G., Davis, D.K., Rottinghaus, G.E., Hill, N.S., Kallenbach, R.L., and Spiers, D.E. (2011). Seasonal fluctuation of ergovaline and total ergot alkaloid concentration in tall fescue regrowth. Journal of Crop Science 51:1292-1296.
USDA Natural Resources Conservation Service. (2015). Web Soil Survey. Accessed at http://websoilsurvey.sc.edgov.usda.gov/App/HomePage/htm.
White H., and Wolf, D. (2009). Controlled grazing of Virginia's pastures. Virginia Cooperative Extension Publication 4180-012. Accessed at http://pubs.ext.vt.edu/418/418-012/418-012.html.
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The authors would like to thank Dr. Mark McCann at the University of Georgia and Dr. Bain Wilson at Virginia Tech for originally lending us the steer to collect esophageal fistula samples. Additionally, the researchers are in debt to Scott Neil for his instruction on proper care of the fistula and cannula equipment. Finally, the authors would like to express their gratitute to Drew Mackey, Brian Brooks and Colby Sheets for their assistance in care for the steer during the project.
Posthumous Authorship in honor of David Fiske. The summer stockpile concept was developed by Mr. Fiske and field tested at the Shenandoah Valley Agricultural Research and Extension Center for more than ten years prior to this work.