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OUTSTANDING ISSUES
- Bioenergetic modules have not been accurately transplanted from BION.
- Angle & distance rules are entirely arbitrary
- initial stocking positions sometimes put wrong species in wrong paddock
- forage production based on summer 2003 but need growth calibration with water, temperature, etc.
- dry matter weathering and disappearance
- 

SIMULATION EXPERIMENTS 

        To compare multispecies with cattle grazing, switch Mixed? on providing two 8 ha pastures, the left one stocked with specified numbers of bison, elk and deer and the right paddock with the metabolic equivalent stocking rate of cattle. Mixed? off divides the pasture into four 4 ha paddocks of which the top row (Paddocks 1 and 2) represent the Kinsella upstream and downstream experiments. The bottom row of paddocks hold elk for the second grazing rotation but offer comparisons of elk followed by deer or bison, respectively.
        To begin the model experiments, press Setup which generates virtual landscapes. These can be edited using Water? and a mouse to place streams or ponds. Pressing Go begins growing the rangeland from a start date of 1 May. On 1 June, the animals are stocked as specified and the run is paused. Pressing Go at each pause generates a new grazing period and shifts animals to the next paddock. At the end of a specified simulation, the paddocks can be Destocked to explore rebound of vegetation as a measure of sustainability.

______________________________________________________________________________________

NSERC STRATEGIC PRECISION RANCHING RESEARCH PROGRAM

Multispecies Grazing Systems

This project models an ecosystem consisting of fescue-dominated aspen parkland pastures grazed by bison, elk (wapiti), mule deer or cattle. The field trials at the Multispecies Grazing Centre, University Ranch at Kinsella address two questions: 

1. Are mixed assemblages of wild ungulates inherently more productive and are natural systems more sustainable than systems based solely on cattle? With the Mixed? switch set on, the paddocks are paired (8 ha) with one stocked as specified and the other stocked with an equivalent metabolic mass of cattle. 

2. Are grazing successions more productive and sustainable than mixed assemblages? Does the sequence matter? Three species offer 6 permutations (3 factorial). Our interest experimentally is to compare successions based on body size (small to large and large to small). When the Mixed? switch is off, four 4 ha pastures are drawn. Paddock 1 is stocked initially with deer and Paddock 2 with bison. The other 2 are stocked with wapiti which replace deer and bison in the second rotation. 

MODELING FRAMEWORK
To explore how animal movements and interactions influence grazing systems, we chose a multi-agent approach in which agents (ungulate species) interact on a dynamic two-dimensional surface of patches (actually cells) with layers representing important forage classes and features such as fences, roads, or water bodies. We chose NetLogo as a more flexible and intuitive platform than Swarm, object-oriented general languages, or GIS modeling extensions. Much of the experimental and observational work derives rules of behavior that underlay emergent properties such as habitat selection, activity budgets and other characteristics.

RANGELAND PATCHES 

Each ha is divided into 100 patches each containing rules for growth of green grass, dry grass, forbs and browse. Virtual landscapes are generated by the Setup button and water bodies, roads and other features can be added using the Water? button and using the mouse to draw their positions. At the moment, initial biomass of forage components are randomly assigned and diffused onto neighboring cells to create a smooth surface.  Further development will represent habitat types obtained from the 2003 rangeland inventory at Kinsella.

UNGULATES 

Each individual agent (bison, elk, deer or cattle) is assigned an initial body weight, grazing efficiency and other distinctive parameters as it is assigned to an initial paddock. At the end of each grazing period, the run pauses and animals are shifted in rotation. 

    Bioenergetics and performance 
This section follows the general approach of Hudson and White (1985). Consumption is based on hourly foraging rates using the disc equation with species-specific saturation coefficients from work on bison and elk conducted at Ministik and cattle at Kinsella. This is allocated among alternative forages reflecting preferences of each species.
Metabolizable energy intake (MEI) is determined from DM intake and estimated metabolizability. Metabolizable energy for maintenance (MEM) is calculated from estimates of expenditures on pastures using bite count and alkane marker methods. The difference between intake and expenditures is ME available for production. It is converted to gain or loss using weight-specific estimates of energy content of gain and associated efficiencies. 

    Movements 
Movement rules involve setting both headings and distances each hour.  Headings are based on: 
    - fences and other barriers 
    - relative preferred forage densities of accessible patches 
    - presence of the same species (gregariousness) or specific leaders identified by personality (e.g. nervousness, dominance), age, or hunger.
    - presence of other species 
Animals are assumed to head towards patches they like and linger there longer. Movement rates are stationary when animals are satiated and bedded, or slow when animals are with the herd and/or feeding on favorable forage patches. Faster rates occur when rejoining groups or passing through poor foraging areas. Responses to disturbance may be added later.

    Time steps 
The model has a basic 1-day time step when vegetation on patches are updated and displayed. Animal bioenergetics, behavior and movements are simulated on an hourly basis. 

CONTROLS AND DISPLAYS 

The interface allows basic plant growth parameters, stocking rates and strategies to be assigned. Once the carrying capacity has been estimated, numbers of each species are established and lengths of the trials determined. The Setup button generates the landscape and prepares to stock animals 30 days (or some other number) into each run to allow May pasture growth before stocking on 1 June. Pressing Go begins the simulation and stocks the paddocks on day 30 then pauses. Pushing Go again resumes the simulation for specified grazing periods (e.g. 15 days), shifts herds to their new paddocks and pauses for the second and third rotations. 

A 2 dimensional map of the rangeland patches and the agents (deer, wapiti, bison and cattle) moving on its surface provide the most dynamic portrayal of the process. Three graphs summarize 1) body weights of animal agents, 2) biomass of green grass, dry grass, forbs and browse, and 3) total forage biomass in each of the four paddocks to assess the impact of grazing treatments. 

USE AND EXPERIMENTS 

The first step is to use linear programming (Excel spreadsheet) to allocate forage supplies by type (grass, forbs and browse to herds of each native species so that balanced utilization is approximated. Stocking rates are adjusted for the Multispecies paddock by doubling the number because of the larger paddock (8 vs 4 ha) then dividing by 3 to account for the longer grazing time (continuous vs e.g. 15 day successive rotations). 

The combined metabolic weight of the ungulate community is converted to an equivalent metabolic mass of cattle for comparison of native vs domestic systems. Stocking rates for the rotationally grazed pasture are recalculated by the program to correctly stock the mixed species grazing trials.  

Note that we assume mixed and tandum systems will be compared so the stocking rates represent numbers of deer, elk and bison for the tandum experiment from which numbers are adjusted internally.

With the Mixed? switch on, determine whether balanced forage utilization by a community of native ungulates is more productive and sustainable than an adjacent paddock grazed by an equivalent metabolic weight of cattle. 

To determine whether interference and other factors influence efficiency, follow this experiment with one in which the Mixed? switch is off. This generates 4 rotationally-grazed paddocks. The grazing trials concentrate on upstream (small to large bodied ungulates) vs down-stream (large to small bodied ungulates). The lower 2 paddocks are stocked with the two wapiti herds needed to provide the mid-sized herbivore grazing rotation. However, they provide an opportunity to determine the impact of the mid-sized ungulate followed by either the smallest (deer) or largest (bison). 

RESEARCH - 2004 GRAZING SEASON
The stocking strategy for the 2004 grazing trials should be based on attempting to balance utilization of browse, forbs and grass by native ungulates. Although optimal solutions did not converge using linear programming (maximizing metabolic weight while holding each forage type within sustainable use), it was possible to to explore rates iteratively using a spreadsheet.  For the upstream and downstream succession experiments, 3 deer, 3 elk and 3 bison are appropriate for each of the 3 replicate 4 ha paddocks. An additional 3 elk are needed to cover the simultaneous 2nd rotation.  Each replicate of the 8 ha multispecies paddock should be stocked by 2 deer, 2 elk and 2 bison (i.e. 2/3 of the grazing succession treatments because animals in the multispecies paddocks have twice the area but are grazed 3 times as long.  The metabolic equivalent stocking rate for cattle is 4 for each of the 8 ha beef comparisons. Our total animal minimal requirements (allow replacements) are:
Successional grazing trials - 9 deer, 18 elk &  9 bison
Multispecies trials         - 6 deer,  6 elk,   6 bison &  12 cattle
Total requirement           -15 deer, 24 elk, 15 bison & 12 cattle           
         
The summer grazing experiment will compare mixed, cattle and tandum systems from 1 June - mid July using a 15 day rotation for the upstream and downstream systems.
For all species and treatment comparisons in 2004 trials, critical animal records include:
         Body weights at the beginning of each rotation and at the end of the trial.  If handling of deer every 15 days creates unacceptable stress, we should look into electronic scales at water points.
         Instantaneous feeding rates (bite rates and sizes) in relation to forage biomass and structure
         Hourly positions from GPS telemetry, videography and direct observation providing measures of gregariousness and evenness of range utilization. 
         Movement rules including probabilities of various activities, headings, distances in relation to forage distribution, herd members and other species.
         Herd social dynamics. Are there temporary or persistent leaders? Is transient functional leadership related to dominance, experience, hunger, nervousness, etc.
Vegetation responses including the interactions of grasses, forbs and browse need to be examined. This is being defined by the Plant Team.

For trials in subsequent years, research will extend to:
        Fine scale analysis, using movable pens, of how grazing by one species influences grazing rates of another.
        Scaling up to daily feeding rates (digestible dry matter intake) using n-alkane markers and daily expenditures using doubly-labeled water. Along with growth rates, this permits calculation of energy requirements for maintenance and growth.  This may have to be limited to elk because of size and hence cost, previous experience with these techniques using this species, and ease of handling.

REFERENCES 

Hudson, RJ and RG White. 1985. Bioenergetic modeling. In Hudson & White, eds. Bioenergetics of Wild Herbivores, CRC Press. 
The Precision Ranching Team
University of Alberta
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