Matney, C., Agriculture & Horticulture Agent, University of Alaska Fairbanks, Cooperative Extension Service

ABSTRACT

Many ranchers and livestock producers utilize western wheatgrass (Pascopyrum smithii) pasture during winter in the mixed grass prairie and shortgrass prairie regions. A high proportion of these ranchers defer grazing on these pastures until the dormant season, commonly known as stockpiling grass pasture. However, few of these ranchers know what the forage value of the stockpiled pasture is during the winter or how this method of forage management compares to a low input alternative such as putting forage in windrows. In this study, we compared putting grass in windrows to stockpiling pasture. Our objective was to determine if cutting western wheatgrass in late summer (last week of September) and putting the grass in windrows would provide superior forage value than leaving the forage to remain standing in the pasture. The study was conducted from 2011 to 2012 in northeast Colorado. Two large western wheatgrass pastures were each divided into two study plots, each receiving a windrow treatment and stockpiled pasture treatment of 8 ha in size. Pastures were excluded from grazing during the study, and pastures had not been grazed since the winter of 2010. Forage samples of the stockpiled vegetation and the windrows were taken from each study plot during the first week of October (within 7 days of cutting), December, and early March. At time of cutting, there were no statistical differences in crude protein (CP), acid detergent fiber (ADF), or total digestible nutrients (TDN) between windrowed and stockpiled pasture.  In December and March, windrowed forage maintained crude protein levels 2% to 1.5% higher than forage left standing in the pasture.  Levels of TDN were 5.7% higher in March for windrowed forage, while ADF levels were 5.1% lower.  The calculated amount of protein supplement needed to meet maintenance levels of cattle nutrition for stockpiled pasture was 206% higher than windrowed pasture.

Introduction

Winter feeding costs are a substantial investment for ranchers in the United States and Canada.  In Nebraska and Colorado, many livestock producers graze cornstalks in the winter to defray feeding costs of cattle.  However, access to cornstalks is not always available and often includes lease and transportation costs.  The majority of cattle producers without access to cornstalks rely on baled forage or grazing of stockpiled rangeland to feed cattle through the winter.   In colder climates, such as Canada, winter feeding of cattle can account for 60-65% of total annual operating costs for cow-calf producers (Kaliel and Kotowich 2002).  A 20-day study of utilizing windrowed pasture versus baled feeding yielded over a 50% reduction in winter feeding costs near Hotchkiss, Colorado (LeValley 1999).  Volesky and colleagues (2002) found that daily feed costs of using windrowed perennial grasses for weaned calves was 53% of those for feeding grass hay.  Other researchers have found that feeding costs (46%) and labor costs (38%) were also lower for windrow grazing (McCartney et al. 2004).  Although there is data to support windrow grazing for economic reasons, there have not been many studies evaluating forage quality of perennial forage grasses in windrows compared to standing forage. 

Generally, higher crude protein (CP), higher total digestible nutrients (TDN), and lower acid detergent fiber (ADF) leads to better quality forage for livestock consumption.  Rangeland management textbooks identify 7% CP as the approximate minimum level needed for most cattle to meet maintenance levels of nutrition (Holecheck et al. 2011).  When CP levels drop below this level, many livestock producers will supplement with protein, especially in winter months when nutritional needs of livestock can be higher.   LeValley (1999) found that utilization of tall fescue in windrows during winter did not require supplementation, with CP values averaging 7.6% (LeValley 1999).  One other study found that windrowed grasses in winter lost protein values much more slowly than standing forage (Volesky et al. 2002).

This study was conducted to determine if cutting western wheatgrass (Pascopyrum smithii) in late summer (last week of September) and putting the forage in windrows would provide superior forage value than leaving the forage to remain standing in pasture.

Methods

The study was conducted from 2011 to 2012 near Peetz, Colorado. Two large western wheatgrass pastures were each divided into two study plots, each receiving a windrow treatment and a control of 8 ha in size. Pastures were excluded from grazing during the study, and pastures had not been grazed since the winter of 2010. Estimated standing forage in pasture from pasture clippings ranged from 2,000 to 2,500 lbs per acre.  During the last week of September, one of the study plots in each pasture was cut and raked into windrows.  A total of four forage samples of the stockpiled vegetation and the windrows were taken from each study plot, within each pasture, during the first week of October (within 7 days of cutting), December, and early March.  Each sample consisted of a subset of three samples taken from random locations across the pasture, no closer than 10 m to each other.  Samples were dried by forced air oven at 105˚C for 16 hours to determine dry matter.  Samples were then ground to 1 mm.  Crude protein values were determined by Leco Nitrogen Analyzer (Dumas Method).  Acid detergent fiber (ADF) and total digestible nutrients (TDN) were determined by Ankom Fiber Analyzer (Kettle Method).

Two sample t-tests were used to compare samples from windrowed and standing grass pasture for three time periods: first week of October, December, and early March.  Statistical analyses were performed using S-PLUS® 6.1 software (S-PLUS 2002).

Results and Discussion

Levels of CP, ADF, and TDN did not differ between standing western wheatgrass and windrowed western wheatgrass during the first week of October (Table 1).  However, in December and early March there were pronounced differences in forage quality between standing vegetation and windrowed forage.  During December, crude protein was 2% higher in windrows (5.7%) when compared to standing vegetation (3.7%).  By March, crude protein was 1.4% higher in windrows than standing pasture.  Values for ADF were 3.2% to 5.1% lower on average for windrows when compared to standing vegetation for December and March, respectively.  Similarly, TDN was higher in windrows by 3.7% and 5.7% for December and March, respectively.

 

		Crude Protein (%)	Acid Detergent Fiber (%)	Total Digestible Nutrients (%)
October	Standing	5.4 ± 0.14	41.0 ± 0.48	51.8 ± 0.38
	Windrow	5.3 ± 0.26	40.9 ± 0.38	51.8 ± 0.36
December	Standing	3.7 ± 0.10a	46.5 ± 0.20a	50.6 ± 0.23a
	Windrow	5.7 ± 0.22b	43.2 ± 0.35b	54.3 ± 0.39b
March	Standing	3.8 ± 0.12a	48.4 ± 0.73a	48.5 ± 0.80a
	Windrow	5.2 ± 0.22b	43.3 ± 0.31b	54.2 ± 0.35b

Table 1. Mean values and standard errors for percent crude protein, acid detergent fiber, and total digestible nutrients for western wheatgrass across three dates and two treatments in Peetz, Colorado.  Values a and b indicate statistically significant differences between means within column and date (p < 0.05).

 

Values for ADF of western wheatgrass left standing in pasture increased numerically throughout the winter.  Similar to what was found by LeValley (1999) and Volesky et al. (2002), CP levels were maintained in windrows while values declined in standing pasture.  Overall, TDN was higher in windrows, and the margin between windrows and standing pasture increased numerically throughout the winter. 

Crude protein levels of forage for both windrowed and standing western wheatgrass were below the minimum cattle nutritional maintenance value of 7 percent.  The overall depressed value of windrowed forage CP is largely attributed to the delayed harvest date that occurred in late September.  The overall CP levels of the western wheatgrass in this study would have likely been well above 8%, if it had been harvested in July at the boot stage of grass development.  The average nutritional deficit for CP of windrowed western wheatgrass in December and March was 1.6%, while the average deficit for standing pasture was 3.3%.  In terms of adjusting rations for cattle in winter, windrows would require less than half the protein supplementation as standing pasture.  To the rancher or livestock producer this could mean reducing protein supplementation costs through the winter by approximately half.  Labor and transportation costs may also be lower with windrowed forages since the higher protein value may allow livestock producers to reduce protein supplementation to once every other day, rather than supplementing daily. 

Conclusion

Harvesting western wheatgrass in windrows provided higher quality forage than leaving grass to remain standing through the winter.  Levels of nutrition, especially CP, were found to be higher in windrows.  Levels of CP ranged from 1.5% to 2% higher in windrows when compared to standing pasture.  Levels of TDN were 5.7% higher in March for windrowed forage, while ADF levels were 5.1% lower.  Both windrowed and standing pasture would have needed to be supplemented with protein to provide maintenance feed for cattle throughout the winter.  However, calculated protein supplement requirements for stockpiled pasture were 206% higher than windrowed pasture.  Even though only modest forage values were maintained by cutting and swathing into windrows during late September, the potential of reducing protein supplement costs by 50% make windrows a viable forage management option.  It is probable that harvesting western wheatgrass in July when it is superior quality, rather than September, would have increased the overall protein content of the forage and further reduced or eliminated the need for supplemental protein through the winter.  Despite the apparent advantage of using windrows, producers should consider harvesting date as well as equipment and fuel costs in relation to potential savings in winter feed, supplement, and labor costs. In order to make informed decisions, producers should also incorporate forage testing as part of their forage management plan in order to insure cattle are receiving adequate nutrition.

Acknowledgements

The author would like to thank the livestock producers of northeastern Colorado for their participation and involvement in this study, as well as Colorado State University, especially the Logan County, Morgan County, Northeast Regional Engagement Center, and Golden Plains Area Extension offices for their support and commitment to research and education in northeast Colorado.

Literature Cited

Holechek, J.L., R.D. Pieper, and C.H. Herbel.  2011.  Range management: principles and practices.  6th edition.  Upper Saddle River, NJ, USA: Pearson Prentice Hall. 444 p.

Kaliel, D. and J. Kotowich.  2002.  Economic evaluation of cow wintering systems — Provincial swath grazing survey analysis.  Alberta Production Economics Branch, Alberta Agriculture Food and Rural Development, Edmonton, AB.

LeValley, R.B.  1999.  Windrow Grazing on the Central West Slope of Colorado.  Colorado State University Extension Web Publication.  Tri-River Area Extension, Colorado State University, Fort Collins, CO.  Retrieved June 5, 2015 from http://trarange.colostate.edu/windrowgrazing.shtml

McCartney, D., J.A. Basarab, E.K. Okine, V.S. Baron, and A.J. Depalme.  2004.  Alternative fall and winter feeding systems for spring calving beef cows.  Canadian Journal of Animal Science 84:511–522.

S-PLUS.  2002.  S-PLUS® 6.1 Software.  Insightful Corporation, Seattle, Washington, USA.

Volesky, J.D., D.C. Adams, and R.T. Clark.  2002.  Windrow grazing and baled-hay feeding strategies for wintering calves.  Journal of Range Management 55:23–32.

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