Summary
By default, animal enterprises are distributed evenly on the farm based on their energy (hence feed) requirements and the availability of food. This can be overridden by setting the location of enterprises (to blocks) and/or changing the relative productivity of blocks (how much feed they grow).
The following diagram depicts what parts of the model the animal distribution information entered in OverseerFM impacts. For a full interactive view of the scientific model in its entirety please click here
Impact
Changing where animals are, changes what animals eat, where they are and hence the nutrients and location of excreta.
Advice
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The model places animals based on feed requirements
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If enterprises graze different blocks, use “Based on animals present”. Only use “User defined” if there is a specific need to model animal grazing that is not based the animal’s feed requirements.
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For relative yield, if you have no measurement of pasture yields, use no difference or yield based on soil and fertiliser, otherwise if you have measured averages for a period of time then can enter these to adjust pasture allocation
Enterprise allocation to blocks
- Same as ratio of total animal intake: Model will allocate enterprises evenly across blocks based on their total energy requirements.
- Based on animals present: The model will allocate ME intake for each enterprise based on the blocks that they have been assigned only.
- User defined: The model will allocate intake to each enterprise based on these percentages.
Relative productivity
Differences in productivity (amount of pasture growth) and livestock type between blocks will influence the distribution of animal intake and excreta deposition between blocks and hence nutrient cycling and transferred between blocks. If characteristics such as soil, climate, developmental status or irrigation differ between blocks then this can result in different farm N leaching losses.
Grazing months
Monthly allocation of enterprises to blocks can be overridden using grazing months.
Care is needed to ensure that relative pasture production is commensurate with the month of grazing. The relative productivity, set the relative pasture production and hence total animal pasture intake from the block. Grazing months determine the months that the pasture production is eaten, and hence the months that urine is deposited on the blocks. Thus, if relative pasture production was the same for all blocks and only one month is selected, then the entire years urine will be deposited on the pasture in that month, with the amount equivalent to the the amount added to the other blocks, but on other blocks the amount would be spread over 12 months.
Water Connectivity
- Access to streams: Checking the access to streams box provides a small increase in N leaching and P loss at the farm scale. The check box is only available for cattle. Sheep are assumed to have access to streams but as all the work shows it makes no difference with sheep, especially for N, as they generally avoid water except to drink it.
- Deer fence line pacing: will increase P loss on blocks with deer grazing on them.
- Deer wallows visible: P loss value of 1 kg P ha/year was added for deer farming systems on land categorised as ‘non-flat’ topography. This is added to the soil P loss component of blocks with deer grazing on them, although the user has the option to indicate that wallows have been hydrologically isolated from streams, a possible mitigation option.
Production
Finishing assumes that the block is mainly used for trading animals where product removal as live weight is higher than a ‘breeding’ operation. This affects the carcass weight sold (kg/RSU) and the proportion of weight sold that is from the breeding mob.