Assessing bulls for purchase
A large component of any breeding plan is sire selection. Beef producers have a range of tools to select appropriate sires, including visual and structural assessments, estimated breeding values (EBVs), selection indexes and fertility assessments. Before the right sire can be selected it is important to establish a well-defined breeding plan for your herd.
Establishing a breeding objective and a breeding plan
The key to genetic improvement and ultimately profit, is to firstly establish a clear breeding objective for the market you are targeting. Once the breeding objective is established a breeding plan can be developed.
A breeding objective should incorporate the following components:
- key profit drivers for the beef business
- an assessment of what the target market is demanding
- current herd performance levels
- future herd production requirements.
A breeding plan should outline the traits that need to be altered within the herd to enable it to reach target market requirements, whilst satisfying the profit drivers of the business.
An example of a breeding objective with a breeding plan is displayed below. Aspects of the breeding plan will dictate what areas the producer will need to focus on when selecting sires for the breeding herd.
|Profit drivers||Current herd||Future herd||Breeding plan|
|Sale weight of steers||170–210kg||200–230kg||Increase steer weight at turn off|
|Fat depth||4–8mm||8–12mm||Improve finishing ability|
|Heifer calving difficulty||10%||<5%||Improve heifer calving ease|
|Weaning rate||85%||>90%||Improve female fertility|
|Mature cow weight||480–520kg||450–500kg||Reduce mature cow weight|
As it will be nearly impossible to find a bull that will tick all the boxes in your balanced breeding plan, choosing a team of bulls that on average meets the breeding objective is the best risk management strategy. In addition, a balanced team of bulls will provide more options, for example, using bulls for heifers and bulls for cows.
A breeding plan helps to develop a balanced approach to using EBVs for selection. Selecting for a single trait alone is not recommended as traits can be correlated resulting in gains in one area but a negative effect in another. For example, 400 day weight and birth weight are positively correlated. Selecting solely for 400 day weight may improve weaner weights but also result in calving problems due to increased birth weight.
A visual appraisal of a bull is important to assess structural soundness. The best genetics in the world will be of no use if the delivery system for these genetics is faulty. The average working life span for a bull in southern Australia is only three years and in the north, five to six years.
Appropriate assessment of sires prior to purchase will help eliminate those with abnormalities that often cause breakdown at a younger age and result in increased bull costs per calf born. A bull breeding soundness examination (BBSE) is highly recommended. The examination covers structural soundness (including the reproductive tract) and an assessment of fertility.
Estimated breeding values (EBVs)
There are many traits which can impact on productivity which cannot be seen by visual appraisal and would take years to measure after introducing a bull to your system.
EBVs provide an insight as to how a bull’s calves are expected to perform on these traits. The other thing to remember about EBVs is that unlike raw data, EBVs are adjusted so that animals are able to be compared on a level playing field.
The model used to create EBVs uses all measurements taken in the field and extracts environmental influences, producing an estimated value of genetic influence alone. Some of the common EBVs available are shown in the table below.
200 day growth
400 day weight
600 day weight
Mature cow weight
Days to calving
Eye muscle area
Retail beef yield
A full explanation of these EBVs is available on Breedplan's page: the traits explained.
The EBV is simply a number which expresses the difference (+ or -) between an individual animal and the herd or breed average to which the animal is being compared.
When looking at a bull, catalogue values for traits are expressed in the units used to measure those traits, for example, kilograms for 200 day weight or centimetres for scrotal size.
For some traits a more positive value is favourable, such as 200 day growth, whilst for others such as days to calving, a more negative value is favourable.
To make sense of EBVs they need to be compared against the breed average EBVs. If the average for the breed 200 day weight is +13 and the bull you are looking at has a 200 day weight of +21 then there are two things you know about that bull:
- He is 8kg genetically heavier than the breed average at 200 days (21-13=8).
- On average his calves will be expected to be 4kg heavier at 200 days than the breed average bull if they were both mated to the same cows. (Half of the genetics come from the sire and half from the dam. 8kg/2=4kg.)
Note that EBVs are calculated on a breed basis. They can only be used for comparing animals of the same breed and against the average of that same breed based on the genetic base of that breed. Across breed comparisons cannot be made.
Percentile band tables are available in most sale catalogues. These allow you to assess where the bull sits in relation to the rest of the breed for the trait you are looking at, for example, if they are in the top 5 or 20% of the breed for 200 day growth.
Accuracy of EBVs
The accuracy under the EBV figure is an indication of how much information has been used to calculate the EBV and the potential for it to change.
The more measurements submitted to the database in relation to that bull for each trait, the higher the accuracy for the related EBV. High accuracies for some EBVs are only obtained once the performance of some of the bull’s progeny has been measured. Breedplan's Interpreting EBV's page provides more information.
Selection indexes or $indexes
Selection indexes or $indexes values are often presented alongside EBVs. A selection index is based on a defined commercial production system producing for a defined market.
They combine several EBVs which contribute to the profitability of that production system and put an economic weighting on each.
The result for each individual is expressed as estimated net profit per cow mated. It is essential when using selection indexes that the most relevant index to your production system and target market is identified.
Each breed has different selection indexes tailored to the common production systems and markets that breed is used for.
To identify the most appropriate index for you:
- read the description of the index
- take into account the main profit drivers within the production system that the selection index is describing
- evaluate the relevant emphases that are being put on each EBV within the selection index.
Note that two bulls may have the same $index but have very distinct EBVs.
When selecting bulls using an index it is important that you also take into account individual EBVs that are particularly important for your system, for example, calving ease if the bull is to be used over heifers.
If you do not think one of the predefined selection indexes suits your needs you can develop your own selection index on the breed object website.
Value for money
Which bull will give you the best return on investment for your enterprise?
A simple calculation can be made which can give you an indication of value for money when comparing bulls using a dollar index. View the Bull earning capacity calculator for more information.
Summary of EBVs
- EBVs provide an estimate of how a bull’s progeny will perform on a number of economically important traits which cannot be easily assessed through visual appraisal.
- Visual appraisal for structural soundness is still required once you have short listed your preferred bulls.
- Testing for reproductive soundness is also important. Many studs now test their bulls before sale.
- Breeding objectives should be defined based on the economically important traits for your production system and target markets.
- Selecting using a single trait is not advisable. A balanced approach should be used taking into account all the economically important traits for your production system.
- Selecting a team of bulls that on average meet your breeding objectives may be the best risk management strategy to meet your breeding objectives.
- EBVs should be compared against the breed average EBVs.
- Each individual breed has its own breed average EBVs and EBVs cannot be used to compare different breeds.
- Accuracies are a measure of how much information has been used to collect an EBV and give an indication of how close the estimated breeding values (EBV) for that trait is to the true genetic value of that animal.
- Selection indexes or $indexes are expressed as expected net profit per cow mated for a defined commercial production system producing for a defined market. They combine several EBVs placing an economic value on each.
- Selection indexes can simplify bull selection but individual EBVs that are important for your system still need to be taken into consideration.