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.

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.

A major change has been to the way the values for Calves weaned /Cows retained is calculated or entered in Version 6.02. Values can now either be entered directly into the cells opposite Calves weaned/Cows Retained (row 16) or values can be entered into rows 11, 12, 13 and 14 to describe the reproductive performance for each age group of females. Once values have been entered in these four rows, the PregTest macro can be run and the Calves weaned/Cows retained values will be calculated and entered into Row 16 against the relevant age groups.

The PregTest macro of version 6.02 applies all of the data entered in rows 11, 12, 13, and 14 for each female age group to calculate all of the Calves weaned /Cows retained values. The PregTest macro of Version 6 required users to enter values for expected conception rate, calf loss, empties sold and pregnant females sold for individual age groups. The PregTest macro of Version 6.02 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. The values shown in Figure 6 are based on the median values for data collected for the Central Forest country type in the Cash Cow project. Data is available for 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.