Example one: Feed-on steers 480 to 580kg
Copy the example scenario (Example one: Feed-one steers 480 to 580kg) from the examples list and open the scenario, this will illustrate how the program may be used in the following example.
Note: Data can be entered or changed in the cells with a yellow background, while the results are displayed in the locked blue cells.
Example one describes taking feed-on steers through from 480 to 580kg live weight on a grain ration. The diet is fed on a ratio of 80:20 grain (80%) to roughage/grass (20%) after a ramp up time of 14 days to avoid acidosis.
In this example there are two different feeds, the grain ration and the roughage/grass portion.
There are two correct ways to approach this scenario.
- The first way, which will be used in this example, involves the user entering the information for each feed separately and save each scenario in the LWG calculator summary section, then use the Feed cost calculator to calculate the combined diet LWG and feed consumed.
- The second way is to enter the information of the combined diet as one scenario by using weighted averages of the information about each feed.
Begin the scenario by typing in the description box an identifiable title i.e. steers 480-580kg (Diet 80:20 grain and roughage) GRAIN portion
Start entering the data starting with the Primary inputs, steps 1 to 4 listed below.
- Metabolisable energy (ME): The grain ration in this example has a ME of 11.32MJ/kg of dry matter. Enter 11.32 in the cell.
- Animal live weight (W): The starting weight is 480kg and target weight is 580kg so enter the mid point of 530kg to reflect an average weight over the time.
- Dry matter digestibility (DMD): The grain portion of the ration has a DMD of 89%
- Animal age in years: In the example the animal is approximately 3 years old.
The next step is the Secondary inputs, steps 0 to 0 listed below, most of these often do not need to be changed between scenarios but check to make sure.
- SRW: standard reference weight or the expected mature weight of the animal where skeletal development is complete and the animal is in body condition score 3, measured in kilograms. The default value here is 660kg, this is the recommended SRW for a Brahman or Brahman cross castrated male, the SRW for the same female animal is 550kg, and for the entire male is 770kg.
- K: a constant value representing the cattle breed, enter 1.2 for B. indicus, 1.4 for B. taurus breeds, or an intermediate value 1.2-1.4 for cross breeds.
- Average walking distance to water, measured in kilometres (km)
- S: enter a constant value of 1.0 for females and castrates (steers, heifers, cows, bullocks), and enter 1.15 for entire males (bulls)
- GF: availability of green forage, measured in tonnes per hectare (t/ha)
- M: the fraction of dietary intake provided by milk (M = 1 + 0.23 x DE from milk, minimum value of M = 1), enter 1 for a weaned animal. This tool is not designed to be used for unweaned stock.
- SR: current grazing density, measured in animals per hectare
- Ecold: additional energy expenditure from cold stress, measured in megajoules (MJ). This occurs when the ambient temperature is below the animal’s lower critical temperature, e.g. at maintenance nutrition, a store animal's lower critical temperature in dry still air is -16 degrees Celsius. In northern Australian grazing systems the Ecold value can be set to 0.
- T: terrain constant, enter from 1.0 to 2.0 as terrain varied from level to steep.
- SD: threshold for grazing density, enter the value 5 for cattle (animals/hectare)
- B: the approximate birth weight of the animal, measured in kilograms. Cattle have a birthweight of approximately 35kg.
Follow these links for more examples of using this calculator:
Introduction to the LWG Calculator: the functionality, assumptions & definitions