The Stock component in Apsim is taken from the Stock component in a CSIRO sister product to Apsim called AusFarm.
AusFarm is produced by the GrazPlan Decision Support Software group in CSIRO (Division of Plant Industry).
GrazPlan Official Website

The Ausfarm-Stock (Stock) component is used in APSIM to graze APSIM-Plant derived crops, such as Lucerne, Lablab and Wheat.

The Ausfarm-Supplement (Supplement) component can also be used as a supplementary feed source for stock.

Management operations can be carried out such as buying and selling of stock, supplementary feeding and moving stock to another paddock.

Currently the paddock sizes are fixed at one hectare.

To use Stock in an APSIM simulation, three companion APSIMUI components are required

·         StockScienceConverter,

·         StockHerbageConverter and

·         FarmwiseSequencer.

e.g.

When Supplement is used, its companion SupplementScienceConverter is also required. e.g.

All of these components are found in the APSIMUI Standard Toolbox in the Animals Folder. e.g.

A sample simulation (Wether_Lucerne_Supplement) of grazing wethers on lucerne with supplementary feeding of wheat is provided under theNew menu.

APSIMUI components

Stock

The Stockcomponent initialises with default properties and no animals.

StockScienceConverter

The StockScienceConverter initialises with the values specified in its properties grid. e.g.

StockHerbageConverter

The StockHerbageConverter initialises with the values specified in its properties grid. e.g.

FarmwiseSequencer

The FarmwiseSequencer initialises with properties specified in its INI file. These properties translate APSIM events to Ausfarm events and should only be altered after consultation with the SEG.

Supplement

Supplement initialises with the values specified in its properties grid. e.g.

The supplement store properties define the initial values of each supplement being used in the simulation. e.g.

SupplementScienceConverter

The SupplementScienceConverter initialises with values specified in its properties grid. e.g.

Pre-defined management rules of stock (cattle and sheep) and supplement feeding are found in the Stock folder under the Management folder in the Standard Toolbox. e.g.

Pre-defined cattle management rules for buying, selling and moving stock.

Pre-defined sheep management rules for buying and selling stock.

Pre-defined supplement management rules for buying, mixing and feeding stock.

Stock Component Description

See the “Stock Component Description” pdf (also comes with your AusFarm Installation
Drivers for the Stock Component

Environmental information

The Stock component implements alternative interfaces to obtain weather data;
I have only provided the APSIM-compatible interface here.

Property	Type	Units	Permitted number of values	Description
time	record	–	Exactly 1	Current time step in standard format.
latitude	double	deg	Exactly 1	Latitude (south is negative).
daylength	double	hr	Exactly 1	Day length including civil twilight.
maxt	double	oC	Exactly 1	Maximum air temperature.
mint	double	oC	Exactly 1	Minimum air temperature.
rain	double	mm	Exactly 1	Precipitation in all forms other than snow.
wind	double	m/s	Exactly 1	Average wind speed
waterlog	double	–	Zero or more	Waterlogging index for each paddock.

Note: The first six of these drivers will cause no difficulty.

The wind driver is used in computing the energy requirement to maintain body temperature under cold conditions;
it can be set to (say) a constant 2.0 m/s if wind speed data are not available.

The waterlog driver is an index that describes the degree of waterlogging of the soil (which is modelled as affecting the time spent grazing);
it is optional and can be ignored in your context.

Paddock information

Property	Type	Units	Permitted number of values	Description
area	double	ha	Zero or more	Area of each paddock.
slope	double	deg	Zero or more	Slope of each paddock

In the Stock component, each group of animals is taken to reside in a paddock.

The list of valid paddock names is obtained by looking for the components that have the area property and then obtaining the names of these components, i.e. a paddock is defined as any entity with an area.
If no component in the simulation has the area property, then the Stock component sets itself up with a single “paddock” that has the null string for its name, an area of 1.0 ha and zero slope.

The slope values are used to compute the energy cost associated with movement.

The usual configuration is to have the paddock components/systems at the same level in the component tree as the Stock component.

Herbage information (plant2stock)
At each time step, the Stock component requests the plant2stock driving property. Each value of plant2stock is allocated to one of the paddocks by parsing the name of the component sending it. The herbage present in each paddock is then summarised before being used in the computations of animal intake. In the case where no paddocks have been identified, all the “plant” components that provide plant2stock are allocated to the null paddock.

Once the intake rates of all animals have been computed, the rates for all animals in a paddock are summed and then allocated between the components in that paddock that provided a value for the plant2stock driver. Each such component is then sent a remove_herbage event that contains the rate of herbage removal for that plant component.

The plant2stock driving property is a record with six fields:

Field	Type	Units	Description
herbage	array of records		Mass and quality of the herbage on offer. The herbage is split into a number of pools that are distinguished by their DM digestibility; each of these pools is described by one element of the array. The fields of the sub-records are set out below.
propn_green	double	–	Proportion of the total herbage mass that is green
legume	double	–	Proportion of the total herbage mass that is legume. Usually 0.0 or 1.0
select_factor	double	–	Species-specific effect on the relationship between digestibility and voluntary intake. Typical values are 0.0 for C3 grasses and legumes and 0.16 for C4 grasses.
seed	array of records		Mass and quality of unripe and ripe seeds (elements 1 and 2, respectively). The fields of the sub-records are the same as for the herbage field.
seed_class	array of integer4	–	“Equivalent digestibility class” for unripe and ripe seeds (elements 1 and 2, respectively). Valid values are 1-6 or 0, where 1 denotes that seeds will be selected at the same time as 80% digestible herbage, 2 corresponds to 70% herbage, etc. A zero value denotes that seeds are not grazed.

Both plant2stock:herbage and plant2stock:seed have array of records as a field.
The fields of the sub-records in them, are:

Field	Type	Units	Description
dm	double	kg/ha	Mass (dry matter basis) of the herbage or seed pool
dmd	double	–	Dry matter digestibility (0-1, not percentage)
cp_conc	double	kg/kg	Crude protein concentration. Can be estimated as 6.25 x N
p_conc	double	kg/kg	Phosphorus concentration. Can reasonably be estimated by assuming a fixed N:P ratio.
s_conc	double	kg/kg	Sulphur concentration. Can reasonably be estimated by assuming a fixed N:S ratio.
prot_dg	double	kg/kg	Protein degradability. In the absence of better information, can be estimated as dmd +0.10
ash_alk	double	mol/kg	Ash alkalinity.
height_ratio	double	–	An index of the bulk density of the herbage. The height ratio for herbage should be computed as 100/(0.03 xBD), where BD is the herbage bulk density in g/m 3 . This value should be set to 1.0 for seed pools.

One way to obtain a distribution of herbage mass into DMD classes is given on page 32 of the technical paper on GrazFeed that can be found at

GrazFeed Technical Paper

 

Supplementary feed information (supp2stock)

At each time step, the Stock component requests the supp2stock driving property. This driving property is optional. The supp2stock property returns the amount and quality of supplementary feed that is present in each paddock. All animals resident in a paddock can access the corresponding quantity of supplementary feed (it is allocated between them in proportion to their maximum intake rate).  To provide this property, include the Supplement component in the simulation.

The supp2stock driving property is an array of records.  Each sub-record has the following fields:

Field	Type	Units	Description
paddock	string		Name of a paddock
amount	double	kg	Amount of supplementary feed present in the paddock
roughage	boolean		TRUE i.f.f. the feed is a roughage.
dm_content	double	kg/kg	Dry matter content of the feed.
dmd	double	–	Dry matter digestibility of the feed (not including any portion that passes the gut undamaged).
me_content	double	MJ/kg	Metabolizable energy content of the feed.
cp_conc	double	kg/kg	Crude protein content of the feed.
prot_dg	double	kg/kg	Protein degradability of the feed.
p_conc	double	kg/kg	Phosphorus content of the feed.
s_conc	double	kg/kg	Sulphur content of the feed.
ee_conc	double	kg/kg	Ether-extractable content of the feed.
adip2cp	double	kg/kg	Proportion of crude protein that is insoluble in acid detergent.
ash_alk	double	mol/kg	Ash alkalinity of the feed.
max_passage	double	kg/kg	Maximum proportion of the feed that will pass undamaged through the gut of ruminants.

DDML definitions

This is for the programmers:

plant2stock:

supp2stock: