March 1, 2024

Weekly genetic review: Longevity and Permanence – is there a difference?

The term Stayability is a commonly recurring theme that emerges with each booming sales season.

Much of the impetus for these discussions is driven by consultants and advisors who seek to encourage producers to consider the cost of a bull and its potential lifespan. However, a Taurus’ work life and tenure are actually two different things.

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

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

However, permanence is not a single characteristic that can be easily selected. There are several factors that impact not only a single heifer’s ability to successfully conceive and raise a calf to weaning, but also its subsequent reproduction.

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

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

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

On a practical level, as a measure of female performance, establishing a benchmark of five calves at six years of age can be a start to addressing issues associated with herd performance. While it may be tempting to want to find a single point of measurement, the reality is that issues such as growth to union, body condition throughout life, as well as genetics that influence factors such as age at puberty or the range of anestrus in Lactation all have a significant influence on conception rates in the single, primiparous and mature cow groups of a herd.

Longevity

As these discussions occur, simultaneous questions arise around longevity within a herd. There is a temptation among some people to use durability and longevity as interchangeable descriptors. However, the two are very different descriptions, and although associated with time in a herd, they mean slightly different things.

Basically, longevity refers to the length of life. In the case of cattle, it generally refers to the length of time a cow will remain in the breeding herd, successfully producing a calf every twelve months. The challenge for longevity is not just the factors that can impact its ability to meet the benchmarks used to define permanence, i.e. five calves at six years of age.

It is also affected by problems associated with structural soundness, including udder soundness. In the case of bulls, it is a term often applied to the professional life of a bull.

Confusion often arises when the discussion begins to interchange longevity and permanence in the context of sire selection. There is no doubt that increasing a bull’s lifespan is highly desirable. Although current data on the average lifespan of bulls is very limited, most industry experts and research suggest that most bulls have a lifespan of between 2.3 and three years.

Much of the early research into bulls and longevity was conducted by Mike Blockey in Victoria. When evaluating bulls over three years of age, his work found that 25% of the bulls were not suitable for breeding. Analysis of this group of bulls showed that:

  • 8pc had mobility problems.
  • 3pc had penile problems.
  • 2pc had a low libido and
  • 9% had testicular problems and/or deficient sperm.

A case of thinking that fixing one problem will solve the other

Again, it is tempting to suggest that because structural soundness has a significant impact on a bull’s working life, it automatically means a reduction in the longevity of the cattle herd. So for many people the argument is that when you address structure, you also address permanence. It’s a case of thinking that solving one problem will solve the other.

There is some merit to this thought. Structurally correct and fertile bulls should achieve higher conception rates.

These bulls must be physically capable of working for more breeding seasons, and these genetics will improve the cow herd. However, this argument is based on the assumption that cows will actually be able to cycle, conceive, give birth and raise a calf. Without managing a herd of cows to meet the ideal requirements for cycling and sustaining a pregnancy, let alone giving birth and raising a calf, program production goals will likely remain unmet.

In other words, the stability of cows within a herd may not actually change.

It is possible to improve the longevity of bulls and cattle herds, as well as improving the ability to reach a benchmark of five calves at six years of age. However, these objectives will require slightly different approaches.

Selection for longevity will be driven, in many cases, by assessment of structural soundness and annual BBSE across the entire team of sires.

While the permanency benchmark requires consideration of traits that contribute strongly to this – such as days until delivery, maintenance of body condition over a year, age at puberty, as well as managing environmental factors to allow these genetic opportunities to be fully expressed.

Alastair Rayner is a director of RaynerAg, an agricultural consultancy service based in NSW. RaynerAg is affiliated with BJA Stock & Station Agents. He regularly lists and sells cattle to clients, as well as participating in bull sales to support client purchases. Alastair provides pre-sale selections and ratings to seed growers in NSW, Qld and Victoria. He can be contacted here or through his website www.raynerag.com.au

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