Dynama+ AECalc
Step 1 - Complete the AECalc worksheet
To assist new users through the initial steps of compiling a budget that includes a detailed livestock schedule, an example Dynama+ file has been provided with the program files, based on the same central Queensland breeding and fattening beef cattle property modelled in the Breedcow+ section of this wiki user manual.
Enter the budget starting date.
This is the source for the year labels on all Dynama+ worksheets and tables, and will also be used to show first and last dates of the budget year to be compiled in the Dynama worksheet.
The AECalc worksheet requires users (for each year of the budget) to:
- identify the starting weight and annual weight gain for all classes of livestock in the herd,
- specify the month of peak calving and the month of sale of each livestock class, and
- specify the ages of sale cattle in months and their weights at sale.
The values entered in the first year of the AECalc worksheet flow automatically to the remaining years of the worksheet but can be overridden if the relative values of the adult equivalent ratings change over time or if the sale weights of livestock change over time.
In Dynama+, as in Breedcow+, the relative grazing pressure exerted by each class of livestock is estimated by comparing each class to a standard measure, in this case one adult equivalent. This is done in the Dynama+ worksheet AECalc, which is identical to the worksheet used in Breedcow+ except that it can have data entered for up to ten years, providing an opportunity to vary the adult equivalent ratings over time.
As in the Breedcow+ program, the calving peak month in AECalc is used to match the various classes of cattle to their birthdays. In this way, deaths, weaning rates and variable costs can be applied from birthday to birthday for livestock classes, i.e. from 12-24 months, 24-36 months etc. Weaners are an exception, since they are rated from 5 months (when they cease to be rated as calves) until 12 months. The other exception is sale cattle, which are included in the model from their “birthday” until the expected average sale month and given a rating in adult equivalents representing only that part of the year.
Weight entries in AECalc are in two groups:
- average paddock weights for each group at the beginning and end of the period selected
- expected average weight (in the paddock) at sale for each sale group. This weight can be adjusted for weight loss between the paddock and the point of sale in the Prices worksheet.
Ensure that weights on growing cattle correspond to the ages at the start and end of the period selected. Mature cows and bull groups have all ages combined, so cannot have start and end weights. Instead we can use “highest” and “lowest” to produce an average, or preferably just use a single weight to represent an average across the group for the whole year.
It is recommended that the "weight at sale" used in AECalc is the actual paddock weight. Entering paddock weights provides the most accurate estimate of adult equivalent ratings for the overall herd. An allowance for weight loss between the paddock and the point of sale can be made in the Prices worksheet.
Estimating the relative grazing pressure exerted by the various classes of livestock within the herd is not quite as critical in the Dynama+ program as it is in Breedcow+, since the herd data being entered is usually based on actual numbers of cattle running on a property. However, it can be useful to allocate an adult equivalent rating to the current herd as a check on the relative grazing pressure being exerted over time as the current herd changes in composition or total numbers. This is especially so for scenario analysis.
Note: Any loaded data will copy over the top of previously entered values.
The AECalc Example
Open the AECalc sheet in Dynama+ and copy the example file Dynamaplus 10 years user manual base herd. Once the file is showing in Dynama+ Scenario List select Open to view and edit the file.
Note that data can only be entered in the cells with a yellow background.
Points to note:
- The standard weight of one adult equivalent has been set at 455 kilograms liveweight. This is a widely used standard measure but can be changed by users if desired. All provided examples use this standard measure and it is recommended that the current value is retained for consistency.
- The peak calving month has been set at 11 (November). This is the typical month of peak calving for the example property and the classes of livestock will be rated from November to November for birthdays.
- All weaners have an average closing weight of 234 kilograms at twelve months of age but this becomes an average opening weight of 229 kilograms for one year old heifers and 239 kilograms for one year old steers. This has been done as the property managers believe that the one year old steers will be almost 5 percent heavier than one year old heifers at the same age. The total opening weight of yearling steers and heifers is the same as the total closing weight of all weaners as the herd is expected to produce 50 percent male and 50 percent female weaners on average.
- Steers are expected to have annual liveweight gains of 180 kilograms for each year that they are held giving the various age groups of steers average paddock live weights of 419 kilograms at 24 months of age, 599 kilograms at 36 months of age and 779 kilograms at 48 months of age in November of each year.
- Retained heifers are expected to gain 171 liveweight each year for the two years they are held separate to the breeding herd.
- Breeder cows are expected to have an average liveweight for any year of 550 kilograms, giving them an adult equivalent rating of 1.21.
- The extra weighting for cows that wean a calf is retained at 0.35. This means that the total adult equivalent rating for the herd is increased by 0.35 for each calf weaned.
- All classes of cattle have been given a sale month and an expected average sale weight.
- The month of sale selected for most classes of cattle is May (month 5) or June (month 6).
--- Once the various classes of weights have been collated in the AECalc worksheet, the next step is to determine the expected sale prices and add them in the Prices} worksheet. ---