Most of us will have heard the statement, '90% of the breeding goes down their throat, probably hundreds of times. It is often said to justify the standpoint that one should worry less about the genetics of the animals and more about how they are managed. And this is partially correct. If you are going to spend a dollar on an animal production system, you should first spend it on some management or nutritional intervention. It is likely that these interventions can result in quick and significant improvements to the bottom line.

Management matters, but genetics still count

That said, we need to be wary of interpreting the statement as meaning that you don’t need to consider genetics at all (in the belief that nutritional, seasonal or management changes will swamp any genetic effects). In reality, to achieve an efficient, productive animal production system that has high welfare outcomes and a low environmental footprint, both genetics and management are important.

While nutritional management and year-to-year variation in feed availability have a big impact on sheep and cattle production, within any given year, on any given farm, in any given flock or herd, there is a large variation in the performance of individuals, and it is this variation that provides the genetic opportunity. Not all of this variation is genetic, but some of it is, and we have good estimates of the proportion of the variation that can be explained by genetics for any given trait. This is called the heritability of the trait.

What we can learn from progeny tests

Progeny tests are a great tool to debunk the 'genetics goes down their throat' theory. Under progeny test scenarios, all animals have an equal opportunity to perform. The single difference between all the animals in a progeny test is their sire. We can use this information to determine the scale of genetic effects for any trait of interest.

As an example, we have taken the data from the Beef and Lamb Genetics progeny tests and plotted out the sire effects on the weight of progeny at 18 months of age (Figure 1). The range in the average weight of progeny at 18 months of age is over 30kg. To be clear, any environmental differences between these progeny groups have been removed. All that is left is the impact of the sire on calf growth. If you consider that only half of the sire difference is represented here, because only half of the genes come from the sire, the actual difference in the genetics for growth of these sires is over 60kg. These sires are some of the industry's leading bulls, and the range in the wider industry will be even greater.

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Within-breed variation

An interesting insight from this data is that there is a complete overlap between Angus and Hereford sires for growth to 18 months of age. There is an important lesson in that. There is as much variation within a breed as there is between breeds. So it doesn't matter what colour cattle you prefer, or the type of sheep that you like, there is a big potential to select for genetically superior ones within any breed or type.

The role of breeding values in selection decisions

Of course, progeny testing is a good way of demonstrating differences, but it isn't particularly helpful for commercial ram and bull buyers to work out which animal to buy. This is the realm of the estimated breeding value (EBV) - or Australian Sheep Breeding Value, for Australian ram buyers. They take all of the known information about an individual sale animal and predict how its progeny will perform in comparison to other sires used. While they are not as accurate as the results from a progeny test, they are definitely sufficiently accurate to help guide a selection and purchase decision.

Insights from the Merino Lifetime Productivity project

The environment can have a huge impact on the total productivity of sheep or cattle. We have grabbed a couple of snippets of data from the Merino Lifetime Productivity (MLP) website to demonstrate this point. You can find all of the site reports at merino superior sires. We have compared data from two different sites and two different years (Figure 2). This data is from the 2015 drop at the Balmoral site and the 2016 drop at the Temora site. Each dot on the graph is the average of the progeny group for a particular sire.

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There is clearly a massive difference in the environment of these two different sheep groups. On first impressions, it appears that all of the sires used at Temora are producing more productive progeny than the sires at Balmoral (ie higher liveweights and higher fleece weights). Fortunately, there were two sires that were used at both sites. Their identity isn't important for the comparison, so we've just called them Sire A and Sire B. What is important is the fact that the sires rank the same for fleece weight and body weight, even though the actual differences between the two sites are huge.

It is really important to understand that although changing the environment tends to result in changes to production and greater total variation between individuals, the genetic difference between animals is maintained. What is also clearly obvious on both graphs is the opportunity available to ram and bull buyers in the sheep and beef sectors of Australia and New Zealand. The total difference in production between sire groups is huge. Importantly, the single difference between groups is the sire; everything else is equal.

Keep these factors in mind when choosing your next ram or bull, and make the most of tools like EBVs to help you remove the environmental noise and focus on the genetics on offer.