Managing and buying bulls

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.

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.

Visual assessment

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.

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.

Breedplan provides more information on selection indexes and selecting animals on selection indexes.

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.

Bull breeding soundness examination (BBSE)

What is a BBSE?

A BBSE is designed to assess a bull’s fertility. The Australian Association of Cattle Veterinarians (AACV) define fertility as "the ability of a bull to achieve, by natural service, a pregnancy rate of 60% and 90% in 50 normally cycling females, within three and nine weeks of mating, respectively".

Fertile bulls are likely to get more cows in calf, earlier in the breeding season and may also have indirect benefits for the future herd.

Scrotal circumference, for example, is not only associated with semen production but also favourably associated with onset of puberty in the bull’s progeny.

Does a BBSE guarantee a bull will perform?

In a BBSE the bull must meet a set of standards determined by the AACV.

If the bull meets these sets of standards for key fertility components then there is a high probability of the bull being fertile. However, it should be remembered that a BBSE is only an assessment of a bull’s present fertility at the time of the examination.

Even if the bull meets all the required standards it is not a guarantee that he will remain fertile until the onset of the breeding season and throughout the breeding season. Injuries, illness and other stressors may all impact on a bull’s fertility (although not necessarily at the time the stressor takes place).

It takes six to eight weeks for sperm to be produced and mature so that they are ready for ejaculation. Any stressors can affect sperm quality and structure during production, resulting in inferior fertility when this sperm is ready for ejaculation several weeks later. Over feeding, especially with a high grain ration, can also negatively affect sperm quality.

Which bulls should I test?

Considering the ability for fertility to change overtime, all bulls should be tested prior to each breeding season, even those that have previously always been reliable.

A BBSE will also find injuries to the penis or sheath which may have occurred the previous season and have gone unnoticed. Completing the BBSE 30–60 days prior to the breeding season will allow time to replace bulls that do not meet the required standards for fertility and give new bulls time to settle in to their new location prior to the onset of joining.

What does a BBSE involve?

A BBSE is carried out by your local vet. There are two basic components to the BBSE:

• A physical examination — can the bull deliver the sperm?
• An examination of the sperm — will the sperm be able to get to and fertilise the egg?

The physical examination

The physical examination will assess:

• General health and condition score — bulls will lose weight during the breeding season so a condition score of 3 is recommended at the beginning of the breeding season. Good health is important as any current illness and associated increase in body temperature may affect sperm development.
• Conformation and locomotion — a bull must be up to the physical activity involved in searching out cows in heat and serving them. Serving cows places a lot of pressure on joints. Conformational weaknesses may lead to bulls breaking down during the season.
• Internal and external reproductive organs — the vet will look for any abnormalities in the penis, sheath and testicles. The scrotal circumference will also be measured. Scrotal size is indicative of capacity for sperm production and is therefore correlated to fertility. It is also correlated to onset of puberty in the offspring. Internal reproductive structure can be assessed via rectal examination.

The semen examination

A semen sample is collected, usually by electro ejaculation. Semen is analysed for:

• density — how many sperm cells are present
• mass activity — how the sperm move as a group
• progressive motility — how well individual sperm move forward (rather than in circles or just twitching with no forward movement)
• morphology — structure of individual sperm cells. This requires a sample to be preserved and sent to a morphologist. The number and type of defects in 100 sperm cells is counted. Defects can result in infertility but can also be transient if they are caused by some of the stressors mentioned above. Not all morphological defects affect fertility.

Who carries out the BBSE?

Contact your local vet to arrange your BBSE.

Bringing home the beef

When bringing home new bulls it is a good idea to settle them in properly in order to prevent problems and maximise future reproductive efficiency.

Bulls can become excited and upset when subjected to a sale situation, transportation and new surroundings. At their new home they can be exposed to different watering systems and feed, new social groupings and new handling methods. A combination of all these factors can upset even the most docile of bulls.

The bull buyer may find that a bull which seemed docile when bought can become aggressive and have a seemingly poor temperament when faced with these stressors. In these situations injuries can often occur.

There are things you can do to ensure your new bull manages the delivery process and settles in easily to his new surroundings. Considering the factors that might make bulls become stressed in the first place will help you to manage this situation.

Checklist from gavel to gate:

• Consider insurance against loss in transit, accidental loss of use and infertility. Remember, ownership is yours as soon as the hammer falls.
• If you are buying bulls from interstate you must ensure all necessary health protocols are followed.
• Separate bulls of different origins during transport.
• If possible transport your new purchase with quiet steers in the truck.
• Minimise stops along the way home as much as possible. Offer bulls feed and water and allow them to rest if you have to stop on a long journey. If you are using a transport carrier:
  • go over handling and resting procedures with the carrier, as well as expected delivery time and truck condition
  • ensure the driver knows which bulls can and can’t be mixed
  • ensure you have the carrier’s number and that they have the relevant identification information (brand, ear mark etc.) and documentation.
• Ensure the bull is treated quietly at all times; eliminate loud noises and dogs from the yards.
• Make the day after delivery ‘health’ day and ensure the bull is up to date with the relevant vaccinations if he isn’t already. Ask the vendor what vaccinations and treatments the bull has had and when they were given. Your local vet can advise on the best vaccination program for your area and help you develop a treatment plan. Vaccinations programs should be completed four weeks before joining.
• Keeping quiet steers/cows in the yards next to the bull for a day or two will help him settle down. Avoid putting the bull directly into the paddock and keep bulls of different origins separate in the yards. 

General bull management

• Bulls should be managed so that they are in condition score 3 at joining. Supplementary feeding may be required. Note that over feeding bulls, especially on a high grain ration, can result in a decline in semen quality and consequently reduced fertility.
• Ensure vaccinations are up to date. Bulls can spread sexually transmitted diseases that can reduce conception and weaning rates. Vaccinations can help prevent the occurrence of such diseases. Disease may also have indirect effects on fertility through associated increases in body temperature affecting semen production or quality.
• Ensure bulls are drenched at the appropriate times for optimal health.
• Regularly check your bulls for injuries during mating. Check for any swellings around the sheath. Ensure the bull is still moving around well and is able to mount (sometimes they can walk well but it’s not until they mount the cow or make the thrust movements that they experience pain, impairing their ability to complete the 'job').
• Take note of cycling behaviour in the females. Remember 60% should be in calf in the first three weeks of joining. If you are still seeing significant amounts of cycling activity in the cows after this point, then there may be a problem.
• Ensure you have a backup plan if a bull injures itself. If you are suspicious about whether a bull is working adequately or not, replace him immediately.
• In single sire mating herds, rotating bulls can help spread the risk of losses due to bull infertility.
• Using two or more bulls in a mob can also help reduce risk of losses due to bull infertility.
• Use bulls of a similar age to reduce time spent fighting rather than serving cows.
• It is recommended that no more than five bulls be mated per 100 females to avoid antagonistic behaviour and fighting between bulls which may result in injuries.
• Select bulls to match cow and heifer herds to minimise calving problems (using EBVs and conformation).
• Keep in mind that yearling bulls may have extra challenges mounting fully grown mature cows.
• Reproductively sound bulls can be joined at a rate of 2-2.5% of cycling females, without jeopardising fertility in most breeding systems. Yearling bulls should be joined to lower numbers and require careful management.
• If synchronisation is used, a higher rate of bulls will be required as most cows will be cycling at the same time.