AUSTRALIA’S rangelands extend to almost 75 percent of the continent, with grazing enterprises located across close to 58 percent of the rangeland environment.

For many producers the challenges of operating a grazing system in an environment characterised by highly variable rainfall are further compounded by the inability to greatly influence the feedbase.

Production is the result of decisions around environmental management and genetic selection. In areas such as the rangelands, where producers are more exposed and have less opportunity to manage the environment, particularly the feedbase, genetic selection becomes a crucial consideration.

Wayne Pitchford

As part of the recent International Rangelands Congress held in Adelaide, Professor Wayne Pitchford of Adelaide University presented to delegates an overview of the importance of genetic selection and applications from research into the maternal productivity projects conducted as part of the Beef CRC.

The key driver of profitability in extensive operations is weaning rate. Unlike conception rates or calving rates, which are stand-alone measures, weaning rate captures both fertility and calf survival.

As a measure for producers, this can become a powerful measurement for maternal performance across mobs and across the overall herd. While this is often a well-recognised concept among producers, moving from a conceptual recognition to practice can remain challenging.

Research from the Beef CRC Maternal Productivity Project clearly demonstrated the importance of weaning rate.

Across large datasets, weaning rate was shown to explain 37pc of the variation in maternal productivity, compared with only 9pc attributed to calf weight. While heavy weaners may be more appealing in the short-term, it is the total number of calves weaned that has the most meaningful impact on enterprise profitability, particularly in feed-limited rangeland systems.

This highlights the need for selection decisions that favour consistent fertility and calf survival over singular focus on growth traits.

Impact of weight and growth

It is worth considering the contributors to successfully increasing weaning rate. A key factor is the impact of both weight and growth rate, particularly for heifers.

The impact of weight and growth of successful conception among heifers is known. Professor Pitchford presented data collected from more than 14,000 commercial heifers, demonstrating that rapid weight gain (>1 kg/day) during joining significantly increases conception rates, even among lighter heifers below 300kg.

In rangeland environments where rainfall events can trigger short-term feed flushes, these events can be used to support joining strategies in response to feed conditions following rain and maximise opportunities to join lighter heifers.

Conversely, where nutritional growth is limited, due to delayed pasture response or overgrazing, heifers must enter joining at a minimum threshold of around 350kg to achieve acceptable conception rates. Without this weight gain and under this benchmark, the risk of missed conceptions increases, delaying entry into the breeding herd and reducing long-term productivity.

Body Condition Score

While weight and growth rate are the major factors underpinning heifers, Body Condition Score (BCS) is the foremost indicator for mature cows.  Research has continually shown that cows that fail to maintain adequate condition through lactation or into the mating period are significantly more likely to experience extended post-partum anoestrus.

In rangeland systems, where supplementation is minimal and feed quantity and quality vary widely, cows with better inherent ability to build and maintain condition are more likely to remain fertile across variable seasons.

This makes condition not only a management outcome but a genetic trait worthy of selection. This can challenge producers who may often focus on selection of traits for growth or carcase outcomes.

Mature Cow Body Condition EBV

In a rangelands environment where seasonal feed flushes are unpredictable, cows that can gain and hold condition in response to these opportunities are potentially more productive.

From a selection process, the Mature Cow Body Condition EBV has significant value for producers. This EBV predicts a female’s genetic potential to maintain condition throughout her life.

For rangeland producers, this is more useful than relying on carcase fat EBVs measured in younger animals.

Wayne Pitchford highlighted that around 75pc of the genetic variation in mature cow condition is independent of carcase fat and muscle traits. This means that selecting for fatness or muscle based on yearling or finishing-stage carcase data will not reliably identify cows that can sustain condition through multiple seasons and reproductive cycles.

For producers in extensive systems, the Mature Cow Body Condition EBV is a more targeted and effective tool for building herds that can maintain fertility under fluctuating environmental conditions.

Focussing on feed utilisation and BCS does also impact considerations on traits such as Net Feed Intake (NFI).

While there is much interest in selecting cattle that are genetically lower for NFI (meaning less feed eaten for the same weight gain), particularly in environments where feed is not as restricted, in rangeland systems, this trait can potentially work against a producer.

Cows that are ‘too efficient’ may eat less when feed is available and struggle to store enough condition to get through dry periods. Research suggests that in extensive conditions, a bigger appetite is an advantage, because those animals can build condition when seasonal opportunities occur.

In addition to these traits, rangeland producers still need to focus on traits that influence production.

Prof Pitchford’s presentation highlighted Days to Calving (DTC) as the most useful EBV for evaluating female fertility. In effect, this EBV offers producers the opportunity to select for two key issues – firstly, the time to conception post-joining and secondly, improving the interval between calving and re-joining in cows.

While a small proportion of variation in DTC is attributed to gestation length, most of the variation reflects post-partum recovery and the conception interval.  This makes the EBV a valuable tool in genetically selecting to improve reproductive efficiency in commercial conditions.

Prof Pitchford’s analysis demonstrated that for every one-day reduction in Days to Calving, producers can expect up to a 4pc increase in calves weaned over two joining periods.

Although rangeland production systems are environmentally challenging, genetic selection offers producers a practical and cost-effective strategy to improve herd performance.

By focusing on traits such as Days to Calving, Mature Cow Body Condition, and overall weaning rate, and applying this alongside sound physical selection, producers can make measurable gains in maternal productivity.

When used well, accurate EBVs provide a framework for building herds that are more fertile, resilient, and better adapted to the seasonal variability of extensive systems.

Al Rayner

Alastair Rayner is Principal of RaynerAg and an Extension & Engagement Consultant with the Agricultural Business Research Institute (ABRI). He has over 28 years’ experience advising beef producers and graziers across Australia. Alastair can be contacted here or through his website: www.raynerag.com.au