How to select a stock bull to breed herd replacements

There is plenty to consider when searching for a new stock bull, including health status, fertility checks, historical management, feeding practices, and if the animal is fit for purpose.

The most accurate way to check whether a bull meets your objectives for your herd is with estimated breeding values (EBVs).

See also: 5 KPIs to measure to improve suckler herd performance

What is an EBV?

An EBV is the best estimate of an animal’s ability to pass on characteristics to its offspring.

Many traits we value in cattle breeding can’t be fully assessed by eye. This is because the raw data on an animal’s performance is influenced by multiple factors.

Genetics plays a part, but so do feeding and management, health status and any careful preparation that may have gone into the sale of that animal – none of which will be passed to its offspring.

EBVs are one of the most accurate measures we have to strip out all that noise and give an objective measure of an animal’s breeding value.

There are EBVs for maternal traits such as milking ability and calving ease, and terminal traits such as carcass quality and growth rate.

Using them can help in choosing bulls that are genetically compatible with the breeding objectives for your herd.

Why are bull EBVs important when breeding females?

A calf inherits half of its genetics from the sire and half from the dam. But often, in suckler herds, there are no EBVs for assessing the dam’s genetics, so sire choice becomes even more important.

Regardless of your end goal for the offspring, it’s important to consider EBVs, especially calving traits.

If you are breeding replacement females, they are essential: you won’t learn anything about the maternal characteristics of a bull’s daughters simply by looking at him.

A recent Nuffield Scholarship by Sarah Pick, AHDB Beef and Lamb knowledge exchange manager, found that fertility traits are five times more important than improvements in terminal traits.

Yet, in the UK, our maternal genetic influence in the suckler herd is falling.

To remain profitable after the Basic Payment Scheme ends, British suckler herds must increase the number of cows calving successfully every 365 days and decrease the average age at first calving.

Improved genetics aren’t a silver bullet, but choosing bulls with good maternal EBVs to breed female replacements will lay a solid foundation for progress.

Interpreting sale catalogues

A typical sale catalogue advertisement for a bull (see “Data for a bull from an advert in a sale catalogue”) includes a range of data that need interpreting.

Indexes

An index is an all-round figure that makes interpreting EBVs easier. It combines several economically important traits into one number.

Accuracy

Each trait is accompanied by an accuracy value, which shows how close the EBV is to the animal’s true genetic value.

I knAccuracy is influenced by the heritability of a trait and what data is available on each animal and its relatives. It is expressed as a percentage.

EBVs change over time as more information comes in, so the higher the accuracy value, the lower the likelihood of variation.

Accuracy values will be highest for bulls with many recorded progeny, such as those used for artificial insemination (AI).

This is great if you are buying semen, but if you’re in the market for a natural-service bull, a lower level of accuracy should be expected.

There isn’t a minimum or maximum accuracy you should be looking for – this is a personal decision for each herd and will depend on the type of animal you’re after.

However, it does help bring some context to the EBVs you have in front of you.

Average 19 calves

This is the benchmark and allows you to compare the EBV of the animal you’re interested in with the breed average. The “19” refers to the calving year set as the benchmark, so this will change over time.

Depending on breed, catalogue formats and trait names can vary slightly, so check with the breed society if you need support.

How to interpret a typical advert for a bull

Self-replacing/Maternal index

This index highlights animals that will produce superior female replacements by focusing on maternal traits such as calving ease and milking ability.

It also includes growth and carcass to ensure these traits are not lost in the slaughter generation.

Positive values equate to greater profitability. This bull (see data in table above) should produce more profitable female replacements than the breed average.

Calving ease

Difficult calvings add cost to a system and negatively affect fertility and welfare. Direct calving ease assesses how easily a bull’s calves will be born, while calving ease (daughters) indicates how easily his daughters will calve.

Here, positive values equate to more unassisted calvings. This bull should produce calves that are born more easily, and daughters that calve more easily than the breed average

200-day milk

This is an indication of milking ability. For sires, this relates to the milking ability of his daughters.

Positive values mean more productive daughters. This bull’s daughters should be more productive and milk better than the breed average.

Scrotal size

Calving at two years is essential to a profitable suckler herd, and larger scrotal size is related to earlier puberty in heifers.

Positive values indicate higher scrotal size. This bull’s daughters should reach puberty sooner than the breed average.

Emma Steele is a beef and lamb knowledge exchange manager with AHDB.