THE term, Stayability is a commonly re-occurring theme to emerge every bull selling season.

Much of the impetus for these discussions is driven by consultants and advisors who look to encourage producers to consider the cost of a bull and its potential working life. However, working life of a bull and stayability are actually two different things.

There is a definition of stayability that is generally accepted by industry, both nationally and internationally: A cow’s ability to wean five calves by the age of six years of age.

Another way to consider stayability is for producers to consider how many daughters of a bull are still within a herd at six years of age.

However stayability is not a single trait that can be easily selected for. There are multiple factors which impact not only a maiden heifer’s ability to successfully conceive and rear a calf to weaning, but also on her subsequent re-breeding.

Proponents of Stayability as a focus of selection point to the benefits offered to breeders, through decreasing the number of replacements that need to be retained in a herd, and through additional weaning weight as a result of the larger number of mature cows in a herd.

While there is some temptation to use stayability as a key selection criterion, as a genetic selection tool there are some challenges.

Speaking at the NSW Angus forum in in Wagga Wagga last year, Dr Matt Wolcott of AGBU highlighted that stayability is a “composite trait, which primarily describes female production.”

At a practical level, as a measure of female performance, setting a benchmark of five calves by six years of age can be a start to addressing issues associated with herd performance. Although it may well be tempting to want to find a single point of measurement, the reality is that issues such as growth to joining, body condition throughout a lifetime, as well as the genetics which influence factors such as age at puberty or lactation anoestrus interval all have a significant influence on conception rates across the maiden, first-calf and mature cow groups in a herd.

Longevity

As these discussions occur, there are the simultaneous questions around longevity within a herd. There is a temptation among some people to use stayability and longevity as interchangeable descriptions. However, the two are very distinct descriptions, that while associated with time in a herd, do mean slightly different things.

At its most basic, longevity refers to the length of lifespan.  In the case of the cow herd, it general refers to the length of time a cow will remain in the breeding herd successfully producing a calf every twelve months. The challenge to longevity are not only those factors which can impact her ability to meet the benchmarks that are used to define stayability, i.e. five calves by the age of six.

It is also impacted by issues associated with structural soundness, including udder soundness.  In the case of bulls, it’s a term often applied to the working life of a bull.

Confusion often arises when discussion starts to interchange longevity and stayability in the context of bull selection. There is no question that increasing the working life of a bull is highly desirable.  While current data on the average working life of bulls is very limited, most industry experts and research suggest the majority of bulls have a working life of between 2.3 and three years.

Much of the early research into bulls and longevity was conducted by Mike Blockey in Victoria. In assessing bulls over three years of age, his work found that 25pc of bulls were unsound for breeding. The breakdown of this group of bulls showed that:

• 8pc had locomotion problems.
• 3pc had penile problems.
• 2pc had a low libido, and
• 9pc had testicular issues and/or poor sperm.

A case of thinking that by fixing one issue it will fix the other

Again, it is tempting to suggest that as structural soundness significantly impacts on a bull’s working life, therefore it automatically means reduced longevity in the cow herd. Therefore, for many people the argument is by addressing structure, it also addresses stayability. A case of thinking that by fixing one issue it will fix the other.

There is some merit in this thinking. Structurally correct, fertile bulls should achieve higher conception rates.

Those bulls should physically be able to work for more joining seasons, and those genetics will improve the cow herd. However, this argument relies on the assumption that the cows will actually manage to cycle, conceive, deliver, and rear a calf. Without managing a cow herd to meet the optimum requirements to cycle and sustain a pregnancy, let alone to deliver, and rear a calf, the production goals for the program are likely to remain unfulfilled.

In other words, the stability of cows within a herd might not really change.

It is possible to improve both the longevity of bulls, and the cow herd as well as improving the ability to meet a benchmark measure of five calves by the age of six. However these goals will require slightly different approaches.

Selection for longevity is going to be driven in many cases by assessment of structural soundness and annual BBSE across the bull team.

While the stayability benchmark will require consideration of traits that strongly contribute to this – such as Days to Calving, body condition maintenance across a year, age at puberty, as well as the management of environmental factors to allow these genetics full opportunity to be expressed.

Alastair Rayner is the Principal of RaynerAg, an agricultural advisory service based in NSW.  RaynerAg is affiliated with BJA Stock & Station Agents.  He regularly lists and sell cattle for clients as well attending bull sales to support client purchases.  Alastair provides pre-sale selections and classifications for seedstock producers in NSW, Qld, and Victoria.  He can be contacted here or through his website www.raynerag.com.au