Breedcow+ Breedcow
Step 5 - Complete the Breedcow+ Breedcow worksheet
Once the Growth Path, AECalc, Prices, and Huscosts sheets have been completed, open the Breedcow worksheet, to complete the herd model and start to analyse the impact of alternative herd management strategies. Note that data can only be entered in the cells with a yellow background.
Section A: Calving and Death Rate Assumptions
This section specifies the calves weaned as a proportion of cows retained and deaths for each class of livestock where relevant. Each age group in this table is labelled with the age at both the start and end of the year and the groupings used should be the same as applied in the AE Calc worksheet. Entries for female classes up to 13/14 years of age is possible.
Values can be entered directly into the cells opposite Calves weaned/cows Retained (%) or values can be entered into the first table to describe the reproductive performance for each age group of females. Once values have been entered in these four rows, the Preg Test macro can be run and the Calves weaned/Cows retained values will be calculated and entered into the Calves weaned/cows Retained (%)row against the relevant age groups.
The Preg Test macro applies all of the data entered in the first table for each female age group to calculate all of the Calves weaned /Cows retained values. The PregT est macro will also calculate values for the percentage sales after mating for female age groups and enter them in Section E: Female Herd Structure when they are entered in Section A and the macro run.
The values for the expected conception rate, calf loss from conception to weaning, empties (PTE) sold or pregnant females sold can be gleaned from pregnancy testing and weaning records. Medium values are available from data collected for the Cash Cow Project. Data is available for Central Forest, Southern Forest, Northern Forest and Northern Downs country types in the Cash Cow project final report. (Downloaded at https://www.mla.com.au/research-and-development/search-rd-reports/final-report-details/productivity-on-farm/northern-australian-beef-fertility-project-cashcow/370
Other entries required in Section A are for the expected mortality rate for each age group of females and males (except herd bulls). Deaths for weaners will be from when they are counted (not necessarily at age five months) to 12 months of age. Deaths on all other groups will be from birthday to birthday (12-24, 24-36 months etc.). Death rates for female stock are calculated against the starting number minus sales minus spays (losses in spayed females are entered separately). The number of cattle sold out of any breeding herd is a function of the original weaning rate and the losses incurred prior to sale.
No deaths are attributed to sale cattle but if the sale month is well after the end of the birthday to birthday rating period and deaths among the sale group are considered to be an issue, additional deaths can be inserted into the same class of livestock for the previous year (or some extra deaths can be added to the kept stock with a suitable adjustment made to the sales percentage) to provide the correct final number of sales. Deaths are normally concentrated in the drier second half of the year, so losses among sale cattle should normally be light.
Identifying the weaning percentage for age groups
For the purpose of identifying the weaning rate for a group of cows, the age headings in Section A (for example the 2 to 3 age group) can be interpreted as if mating were at the first age (2) and weaning at roughly the second, even though physical weaning is likely to be at some point beyond the second age (3). The fact that the mating occurs towards the start of this period is the key issue. The outcome sought is an accurate estimate of the number of calves produced from this mating, though they are called “weaners” to allow for losses between birth and weaning.
Entering weaning percentages in the Breedcow worksheet
In the model, weaning rates are entered as the number of weaners produced as a proportion of the number of cows mated and kept and not just the cows mated. (Note: This is calculated automatically if the PregTest macro is used – see section A above) This is done either manually or by using the PregTest macro and is different to the usually applied calculation of weaners produced from cows mated. Where weaning rates are being manually entered, some adjustments may have to be made to ensure that the correct number of weaners is produced by the herd being modelled.
For a breeding herd where all the cows are kept in the breeding herd for the entire period between mating and weaning, the weaning percentage will be based on the total number of cows mated. For example, if 100 cows are mated and all are kept with 70 calves weaned; the weaning rate for that group of cows in Section A will be 70 percent and will be entered as .70 in the Dynama worksheet in row 16 and the correct column for the female age group.
For a breeding herd where some cows are mated but sold after mating and prior to weaning, the weaning percentage will be calculated on the total number of cows mated and kept.
For example, in a 100 cow breeder herd where 80 breeders are tested pregnant, non-pregnant cows are sold prior to weaning and 70 calves are weaned, the weaning rate from cows retained in Section A will be entered as 87.5 percent (70/80) AND the sales after mating (Section E) will have the value 20 percent inserted for that group of females. In this case the value shown at the bottom of Section E of the Breedcowplus worksheet for Weaners/all cows mated should show 70% - the value for the true calculation of weaning percentage.
The “true” weaning rate is the number of weaners produced from cows mated. The calculations behind the weaning percentage for each age group calculated as a percentage of the cows retained AND as a percentage of the total cows mated.
Section B: Sale Prices
This should reflect the prices previously entered in the Prices worksheet. Changes should be made in the Prices worksheet, not in this section. Ensure values are entered for all age and sex groups up to the maximum male turnoff and cow culling age. These prices are used to value sales and to place a capital value on the herd. Missing values cause the herd to be undervalued when asset values are being calculated. Filling in values and sale weights in the AECalc and Prices sheets beyond normal sale ages also allows some “what if” calculations to be undertaken on older male turnoff or a change to the mix of heifers and cull cows sold (which may require some being sold older or younger). Sale age is specified as Weaners, 1, 2, 3 up to 14 years for female classes and up to five years (60 to 72 months old) for steer classes. Animals may be sold mid-year (18 months, 30 months) using the age labels 1, 2, 3, so long as the prices and sale used are correct for those mid-year ages. Ages in months for sale cattle are specified in AE Calc.
Section C: Steer and Bullock Herd Structure
This is used to configure the turnoff strategy for steers. Steer turnoff can either be “all at once” at one age or spread over a number of age groups.
The number of steers at the start of the year in the “0” group (weaners) is half the number of calves weaned. The number surviving to age 1 will be the opening number less deaths (from Section A), less any sales. Steer deaths are calculated on the opening number less sales. Calving typically peaks about November / December in northern Australia and sales occur normally from May to June. It is therefore likely that the age of turnoff for steers is really at about 18 months, 30 months, 42 months or 54 months to fit in with seasonal growth patterns. When sale ages are part way into the designated year make sure that the prices specified are really for 18 months and 30 months, even though the labels say 1 and 2. All herd numbers in the Breedcow worksheet are calculated to multiple decimal places, but displayed as integers. This level of precision is needed to achieve a balance in stable state, but can cause rounding errors in the display (for example, a worksheet may show 113 steers aged 3 when a calculation based on whole numbers may only indicate 112). Splitting steer sales across age groups Where male turnoff is to be only one age group, set all cells for Optional sales % to zero, and enter a value corresponding to the year of sale in the maximum male turnoff age cell. For example, if all steers are to be sold at three years old, a 3 needs to be entered as the maximum male turnoff age and zero’s need to be entered in the optional sales percent row. Where steer sales will be undertaken at multiple ages, the oldest age group is sold by an entry in the maximum male turnoff age cell which corresponds with the maximum age of sale. Optional sales are shown as a percentage of the opening numbers under each age group in the Optional sales % row up until the maximum sale age previously entered. For example, it is possible to specify a maximum turnoff age as 3 but sell the top 50 percent of the steers at 2. Where turnoff is based on animals achieving a particular weight before they can be sold and sales can occur over more than one year, estimates of the proportions of the herd likely to be sold in each year can be made in the Splitsal program. Splitsal will estimate average weights and prices for a group of sale cattle based on estimates of their current live weights and potential growth rates. The impact on the average liveweight of a group of steers of selling the lead also needs to be considered when applying optional sales across a number of age groups. Selling the better steers out of a group of steers is generally expected to result in the average weights of the mob the following year being less than they would have been had the whole group been carried through. The Splitsal program can provide some help with this issue in that it can be used to identify the average weight of the “lead” and the average weight of the “tail” of a mob of steers.