Acoustic analysis: A novel way to measure livestock grazing behavior

Project Overview

Project Type: Graduate Student
Funds awarded in 2014: $10,981.00
Projected End Date: 12/31/2015
Grant Recipient: Virginia Tech
Region: Southern
State: Virginia
Graduate Student:
Major Professor:
Gabriel Pent
Dept. of Crop and Soil Environmental Science, Virginia Tech
Major Professor:
John Fike
school of Plant and Environmental Sciences, Va Tech

Annual Reports


  • Animals: bovine


  • Animal Production: feed/forage
  • Crop Production: silvopasture


    Wideband acoustic recordings were verified as an accurate method for documenting sheep foraging behavior, and time lapse cameras were deployed in place of GPS loggers to confirm sheep behavior due to logger inaccuracy. Preliminary results indicate that lambs in open pastures spent less time lying down in comparison to lambs in the silvopastures. Contrary to expectations, lambs in open pastures spent more time grazing with higher bite rates, though these grazing events were confined to mornings and evenings. Lambs in honeylocust silvopastures had highest afternoon body temperatures. Despite these variabilities, lambs in the honeylocust silvopastures had the highest weight gains.


    This material is based upon work that is supported by the National Institute of Food and Agriculture, U. S. Department of Agriculture, under award number GS14-130.


    Project Relevance to Sustainable Agriculture


    Human population growth is increasing global demands for food and fiber production at the same time that the agricultural landbase and the resources for agricultural production are in decline (1-3). Concern about climate change and dwindling natural resources has led to a public push for decreasing environmental contamination (4).

    Agroforestry offers opportunity to fulfill the demands both for increasing food and fiber production, while also improving environmental quality through increased nutrient utilization, reduced sediment runoff and erosion, and increased carbon sequestration (5-9). These diversified systems are managed so as to take advantage of positive interactions among system components and thus create greater output than monocultural production systems. Simple monocultures of pasture and animal systems have appealed to livestock producers in the past, as this simplifies management. However, the sustainability of such reductionist methods is being called into question (10) and systems that take advantage of complexity and diversity will be more productive and sustainable.

    Silvopasture, one of five agroforestry practices, integrates trees with pasture-based livestock systems and provides both short- and long-term returns from the same land base (11). Livestock in silvopasture systems can benefit from shade in summer and from shelter from wind in winter. The trees in turn benefit from the managed livestock presence through amplified nutrient cycling and weed suppression (11). Along with potential benefits to food and fiber production, silvopasture systems may have increased soil organic matter with improvements in microbial health and nutrient cycling (12), greater water storage (13), and improved nutrient capture and retention (14). These factors, coupled with improved soil conservation and nutrient utilization, result in regional watershed benefits (15). Silvopastures sequester more carbon than timber plantations or pastures, an advantage with global ramifications (16). Along with these production and environmental benefits, silvopasture systems may require less nutrient and herbicide inputs; increase and diversify marketable productions; and produce aesthetically-pleasing landscapes that add value to farms and rural economies.

    This project is part of an on-going effort to develop sustainable silvopasture production systems. My research addresses the animal behavior and welfare dynamics of silvopasture production and will develop tools to enable researchers to implement and monitor these systems. This project also addresses the productivity of these systems, a component critical in convincing farmers of the economic sustainability of silvopasture. As part of an existing SARE grant, we will monitor system production metrics (forage yield and nutritive value and animal performance). Support for this graduate student grant will allow us to meet the following objectives and better understand the mechanisms supporting animal performance in silvopastures.


    Statement of Problem, Rationale, and Justification


    The purpose of this project is to compare behavior and well-being of grazing livestock in deciduous silvopastures with that from open pasture systems. Our previous SARE-supported research has shown that tree species have differential effects on pasture composition; forage yield and nutritive value responses can be positive or negative depending on tree age, stand density, and slope position, among other factors (17, 18). This has not translated into differences in animal performance among systems, however.

    Few studies have explored how temperate silvopastures designed and managed with deciduous trees affect both the forage base and the performance and behavior of grazing ruminants. Forage production and nutritive value vary quite widely depending on tree species and management, making relationships to animal performance more difficult to determine. Thus, while deciduous silvopastures may differ from open pastures in terms of forage yield, composition, or nutritive value, these responses do not necessarily track differences in animal performance between silvopastures and open systems (19-21).

    Recent research (22, 23) with lambs grazing in walnut- and honeylocust-based silvopasture systems suggests animal performance is comparable to that from open pastures, even when forage yield is reduced. However, the mechanisms behind these responses have not been clearly defined. Some data suggest that increased forage nutritive value compensates for lower forage mass in silvopastures (e.g. 21), but lower soluble carbohydrates (18) and only moderate, variable responses in terms of fiber digestibility (23) challenge this idea. Altered animal behaviors – such as grazing time, rumination, standing, and lying – and consequences to energy expenditure may thus be more important drivers of the similar animal gains observed between open and silvopasture systems.

    Animal behavior in silvopasture has not been well studied. Heat load may change activities and intensify stresses experienced by animals in open pastures, thus increasing time and energy spent in behaviors to stabilize body temperature. Ambient temperatures are lower and less variable in silvopasture systems; thus, animals may experience more time with conditions suitable for grazing and increase dry matter intake (DMI) (24). Distinguishing between reduced energy needed for maintenance vs. greater opportunity for grazing in pasture systems is challenged by the limited tools for monitoring grazing animals, and current methods involve time-intensive observations.

    As part of a larger, SARE-supported study evaluating forage production and animal performance in silvopastures, this project will generate detailed information on animal behavior and heat load in silvopastures and open pasture systems. Specifically, we will: 


    1) Use novel acoustic monitoring systems to determine lamb grazing behavior; 

    2) Apply GPS tracking systems to determine shade distribution patterns and animal mobility and position relative to shade in silvopastures; 

    3) Monitor lamb temperatures with temperature sensors; and 

    4) Integrate information on forage quantity and quality with spatial and temporal information on grazing behavior and body temperatures to understand the effects of silvopasture dynamics on animal performance.


    This research will increase the body of information regarding factors affecting animal performance in silvopastures and support the development of these sustainable land management systems.


    Literature Cited


    1. Tilman, et al. Proceedings of the National Academy of Sciences, 108(50), 2011: 20260-20264.
    2. Pimentel, et al. Science, 194(4261), 1976: 149-155.
    3. Tilman, et al. Nature, 418(6898), 2002: 671-677.
    4. Chen, et al. Proceedings of the National Academy of Sciences, 108(16), 2011: 6399-6404.
    5. Nair. Netherlands: Springer, 1998.
    6. Wallace. Agriculture, ecosystems & environment, 82(1), 2000: 105-119.
    7. Tscharntke, et al. Biological Conservation, 151(1), 2012: 52-59.
    8. Young. Outlook on Agriculture, 19(3), 1990: 155-160.
    9. Montagnini & Nair. Agroforestry systems, 61(1-3), 2004: 281-295.
    10. Lyson. Trends in Biotechnology, 20(5), 2002: 193-196.
    11. Sharrow, et al. In North American Agroforestry: An Integrated Science and Practice, by Garret, 105-131. Madison: American Society of Agronomy, Inc., 2009.
    12. Chander, et al. Biology and fertility of soils, 27(2), 1998: 168-172.
    13. Sharrow. Agroforestry systems, 71(3), 2007: 215-223.
    14. Michel, et al. Plant and soil, 297(1-2), 2007: 267-276.
    15. Shrestha & Alavalapati. Ecological Economics, 49(3), 2004: 349-359.
    16. Sharrow & Ismail. Agroforestry Systems,60(2), 2004: 123-130.
    17. Buergler, et al. Agronomy journal, 97(4), 2005: 1141-1147.
    18. Buergler, et al. Agronomy Journal 98(5), 2006: 1265-1273.
    19. Peri, et al. Proceedings of the New Zealand Grassland Association 63, 2001: 139-147.
    20. Lehmkuhler, et al. Agroforestry systems, 59(1), 2003: 35-42.
    21. Kallenbach, et al. Agroforestry systems, 66(1), 2006: 43-53.
    22. Fannon-Osborne. M.S. Thesis. Virginia Polytechnic Institute and State University, 2012.
    23. Fannon-Osborne, et al. In preparation, 2014.
    24. Mitloehner & Laube. Journal of Animal and Veterinary Advances 2(12), 2003: 654-659.


    Project objectives:

    1. Develop and apply novel acoustic monitoring systems to quantify lamb grazing behavior in terms of prehensive biting events and rumination;
    2. Quantify lamb body temperatures diurnally; 
    3. Determine diurnal behavior (and shade utilization in silvopastures) using GPS tracking systems and remote sensing technology; and 
    4. Integrate information on forage quantity and quality with spatial and temporal information on grazing behavior and body temperatures to understand the effects of silvopasture systems on animal performance.


    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.