PHYSICAL appearance of an animal is the result of the interaction of its genetic potential with the environment in which it lives. Environmental influences can be considered at both a macro and micro level.  Each level does play a role in how well an animal is able to express its genetics and contribute to the production goals of an enterprise.

At a macro level, nutrition is the key driver. Daily energy intake drives not only the potential for growth and weight gain, but determines other physical functions including lactation, oestrus and semen production.

Often the ability of an animal to achieve production benchmarks is more a result of the management strategies around nutrition as well as the timing of management events than the genetic potential the animal has.

At a micro level, environmental factors also may have an impact on an animal’s level of production. Adaptation to heat or cold, tolerance of parasites or ability to withstand disease all contribute to animals’ ability to fully express their potential.

Breeding objectives in many programs often focus on high level outcomes. These include the ability to achieve desired fertility levels within the breeding program, to achieve market compliance for carcase specifications or levels of eating quality.

Cattle for country

In turn the selection pressure placed on potential sires and on replacement females often reflects these high level outcomes. However the most effective breeding objectives also reflect the need for cattle to be suited for the environment in which they are to be grown in.

Breeding ‘cattle for country’ has long been at the forefront of many producers’ minds.  Ensuring that cattle selected for a program are adapted to cope with the challenges of temperature, parasites or finishing programs should have a level of priority on par with more frequently considered traits such as growth.

The challenge is knowing how to select the animals that are both adapted and genetically superior in order to make progress in an enterprise.

Environmental adaptation occurs biologically or behaviorally. Many behaviours are acquired as cattle observe others and learn to adjust to the actions of the herd. This can often be seen in grazing patterns, maternal behaviour to protect calves or knowledge of plants to avoid.

To some extent producers have looked to select cattle from environmentally similar areas in order to capture some degree of behaviour adaption.

The greater challenge is when producers need to select livestock that may have been bred in quite different environments and have been chosen in order to make genetic improvement.

Individually, those animals can learn over time to adapt to the new environment. However this period can take some time to occur. It’s also important to remember than behavioural adaption is not a heritable trait. To some degree, cattle have to learn from one another in order to express those behaviours.

Adapting to environmental challenges

While behavioural adaptation is an important component of animal performance, it is the genetic differences each animal has, which results in the variation of the expression of traits.

Put simply, some animals within a given breed are genetically superior to others in their ability to cope with environmental challenges.

Within breeds, these differences can be assessed and described as part of an Estimate of Breeding Value.

In recent years, several breeds have started to consider the development of EBVs to identify animals which have greater genetic superiority to adapt to environmental challenges such as parasites, heat and disease.

Parasite resistance is a key example of the variation in animals’ ability to cope with an environmental condition.

Brahman and tropically adapted breeds are generally known as having greater resistance to parasites than British or European breeds.  However within the population of Brahman cattle, there is broad variation in animals’ resistance levels. As a heritable trait, producers who select for this trait – along with the major production traits – can work to shape their herd towards a more adapted herd for their environment.

Angus Australia is also working on a number of research EBVs in order to offer producers the opportunity to select animals that are genetically more adapted to an environment.

Two key examples include coat type and disease resistance research EBV.  Coat type is often a focus for producers considering an animal’s ability to cope with temperature, or for animals that may be finished in environments that are wet and muddy such as a feedlot.

In these cases, slicker and shorter coats offer an advantage for the animal. While this may only be a small advantage, having an animal coping better with conditions allows it to more freely express its potential for growth and so achieve production targets more efficiently.

US study focuses on the genetics of adaptation

In the United States, the genetics of adaptation have also been a focus for study. A recent study by Prof Jared Decker from of the University of Missouri considered the genetics of environmental adaptation.

The study published in PLOS Genetics, reflected that in the US, cattle have been losing some of their genetic adaptations that have allowed them to fully express their genetic potential in various environments. These adaptions range from heat tolerance to an ability to live in higher altitudes such as in Colorado.

However since the 1960’s, these genetic adaptions have been gradually diminished, largely through the use of sires that, while highly placed for production traits, have not been selected with environment in mind. The US work opens up the opportunity to genetically test for specific environmental adaptions, in order to allow producers to consider selection for the most suited animal for their program in both production and adaptation.

The essential messages for Australian producers is to recognise that adaptation to the production environment – regardless of geographic location – should be part of a breeding objective. While some adaption can be acquired, longer-term, ensuring adaptability is part of the genetic profile of a herd will result in more environmental improvements.

As more genetic information is collected on animals including the resistance to parasites, shortness of coat or resistance to disease, the greater the opportunity is for producers to start building this profile in their herd.

More significantly, for producers who already have genetically-adapted animals, well suited to their environments, the availability of this information should be seen as a way of selecting animals that will not lower the level of adaptation in a herd.

It is important when seeking to improve production traits, that other important traits such as environmental tolerance are not overlooked or under-appreciated. The risk of long-term changes in adaptation can see any potential production improvements lost as animals become less able to cope with the challenges of their environment.

 

 

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