We use a mating strategy that is best described as "corrective mating". Essentially, this means we are trying to find sheep that complement each other. Not to be confused with complimenting each other... Even if you succeeded, you would create very amicable mating relations, but I doubt it would result in any great genetic gain!

In all seriousness though, I don't believe there are any perfect sheep. Even if we found the perfect sheep, I am sure we would still try to improve it!!

 

This ram also thinks that joke was terrible.

 

Instead, each sheep has strengths and weaknesses. As a basic example, often ewes with the softest, finest, most beautiful wool are among the skinniest. Conversely, the biggest, fattest ewes tend to have stronger, duller wool.

 

In corrective mating, we would join the better wool rams over the better frame ewes, and the better frame rams over the better wool ewes. This is how we used to join prior to developing the stud. It means you might keep sheep with some wool types you don't like because they have exceptional doability. Or you will keep some smaller, skinnier sheep because they have wool that you love.

 

Other Philosophies

Another school of thought would only use rams that are good all round and fit a designated "type". This passes over sheep with exceptional individual traits if it's not quite up to standard in another trait. This is the "peas in a pod" philosophy that hopes to just incrementally improve the average over time.

 

Another philosophy is line breeding. In this case, you would try to find a ram who is closest to your picture of an ideal sheep, and then try to "lock in" those traits by, for example, joining fathers over daughters. Once you have a particular favourable set of traits locked in, you might try to improve by adding in something else.

 

I can see their advantages, but as overarching philosophies they inherently result in a narrower, less diverse genetic pool. While there are downsides to having a diverse genetic pool, we believe that you can make faster genetic gain by having a larger genetic pool. Once you lose genetic variability, it is gone. Take poodles for example. Imagine trying to breed that thing back into anything resembling a useful dog without outside genetics...

 

5.5-month-old ram lambs

Genetic Diversity

Breeding is far more complicated than this, but I'll demonstrate with a simplistic 2 trait example. Let's take a ewe who has the best set of genes in the world for trait 1 but the worst set of genes for trait 2 and join her to a ram who has the best genes for trait 2 but worst for trait 1. In this overly simplistic example, the resulting progeny could fall anywhere on the spectrum for each trait from worst of each to best of each depending on which genes were inherited.

 

Compared to joining two sheep who were average for each trait and produced progeny that were about average, the first example has some better sheep, some average sheep, and some terrible sheep. With enough reproductive power, the variability is addressed by culling. If you have 130% weaning rate and turn over 1/3 of your ewe base each year, you can cull around half of your ewe lambs.

Is it environment or genetics causing this difference in condition?

Complexity

The example above is far too simple. No-one really understands the genetic and biological pathways that result in the expression of many traits. Most traits are not expressed from a single, or even small group, of genes. Instead, most traits are the result of a complex interaction across many, many genes. Thankfully, we can still make significant genetic gain just by measuring the expression of traits without knowing the individual genes or the genetic interactions that cause them.

 

I suspect that there is more that we don't understand about genetics than we do understand. There is an emerging field called epigenetics, which is showing that living creatures seem to switch genes on and off due to their behaviours and environment.

 

Corrective mating could be taken to an extreme. You could keep otherwise good sheep that have black spots, or bad shoulders, or bad feet or any number of faults because they have desirable traits. It would become a headache trying to keep track of which animals could have inherited which faults.

 

Setting limits

In light of this complexity, we believe it is wise to still set limits on some traits, and maintain a balance of traits.

 

There are traits that we want to lose genetic diversity over! We cull anything that gets wormy or flyblown, fails to wean a lamb or has a speck of black wool. We are very hard on anything with structural faults (feet, shoulders, hocks, etc). Balance means it isn't worth keeping a ram that is exceptional in only 1 or 2 traits but lacking in most others.

 

Example sires

Now that I've completely bored you with the reasoning behind what we do, let's look at some examples.

One of our best performing sires is 190791. He has a rare combination of high doability and exceptional quality, fine wool. Phenotypically, his wool is super soft and has outstanding character and brightness. He has a beautiful temperament, good depth of body, and stands very well on his feet. The only downside is that his shoulder may have a slight dip.

 

Genetically, his ASBVs are pretty solid. High fat and muscle, great WEC, extremely low FD, and solid ERA. His main fault is lower fleece weight and growth, though at least he has better early growth relative to adult weight.

 

So now there are two ways of mating him. Firstly, we can look at it from the point of view of how to produce a better version of himself. In this case, we want to find ewes that have exceptional fleece weight and growth, with perfect shoulder structure. Hopefully he will throw some progeny with all his strong points but also a few of his weaker points improved.

 

From the flip point of view, we can use him as a tool to improve something in the ewes. If a ewe comes through that is otherwise a good animal, but is growing harsher or broader wool, we can join her to 190791 to improve those traits.

 

Another example is 201737. He is a fantastic looking sheep with great depth and width of body and bright, white wool. He has huge growth, fat and muscle. He just doesn't have a lot of staple length, and he is broader micron. So, he will get joined to the smaller framed, pretty, heavy wool cutters to give them a bit more oomph in the carcass.

 

Classing time

At classing then, we have a board in front of us with a list of what we think are the most important traits for each ram. We have their strengths and weaknesses highlighted and a couple of brief notes.

 

Each ewe comes through the classing box one at a time. First we take a step back and look at her overall body shape, constitution and structure, and run a hand over her back to get her condition. Then we open up her wool at several points to feel and look at her wool type and quality. Finally, we look over her ASBV data on the screens in front of us.

 

Based on all that information, we make a judgement call as to whether she has enough good points and few enough bad points to be useful in the stud. We also have a self-made index, developed through neXtgen Agri, that helps give an indication of the overall balance of traits we think are desirable.

 

Then we ask ourselves the two questions:

What does she have that another ram needs added?

What are her weaknesses that need improving?

With that in mind, we might have a quick discussion amongst ourselves and settle on the ram that we think provides the best chance of success.

 

We also have a backup solution of using technology to help. There is a tool called Matesel which uses ASBVs to match ewes with rams to create the most genetic gain with the least amount of inbreeding. The big weaknesses are that it cannot take into account structure or wool types, and it mainly uses an index so it is difficult to make it do a great job of improving individual traits.

 

However, it is very useful for sheep that we would be happy to join to several different rams, and for sheep that are generally good all-round animals. It is also useful as a buffer so that we don't have to worry so much about how many ewes are joined to each ram. If we have about 15% classed this way, we can tell Matesel to give those ewes to the rams that need a few more, while avoiding rams already mated to 90 or 100 ewes.

 

After we get into classing and get familiar with the list of rams, we can go through about 100 ewes per hour.

Mating for the commercial producer

Of course, we have a lot more tools and data to work with because of our meticulous data collection within the stud and the resulting ASBVs. Nevertheless, you can still make significant gains with visual classing. Hopefully you at least have ASBVs on your ram team.

 

The simplest form of corrective mating is to separate all ewes into two groups: wools and frames. Join the wool rams over frame ewes; and join the frame rams over wool ewes. In merino production, we are always trying to find that balance between high quality, high fleece weight wool and high-quality, fast-growing lambs.

 

Wool

This needs another whole article, but in essence you are trying to select for high density wool (more secondary fibres per square mm of skin). There are several indicators:

Crimp depth. Deep, horseshoe crimp that is even and crimping from the skin to the staple tip

Clearly defined bundles. The fibres should be well aligned and forming smaller bundles.

Softness. Finer micron and density go hand in hand, producing the softness of wool.

Bright, glossy white. Good wools should be a bright white, indicating a good wax covering that doesn't let water penetrate. This differs to the dry, "chalky" white.

Skin type. The skin of high density wool should be supple and pliable, able to be lifted away from the sheep.

 

Frame

These should be fertile, well-built animals with good doing ability. Don't fall for the trap of just selecting the biggest animals for frames, though obviously extra small animals are also not desirable! You primarily need to be looking for:

Depth. Deep across the chest and barrel.

Width. Wide across the rump and deep in the twist.

Condition score. Run your hand over the loin to feel the fat and muscle cover.

Size. Not too small but not too tall and leggy either.

 

Practical steps

1. Decide on an identification system

If you are not using EIDs yet, you will need a way of identifying which way you class your ewes. Here are a few suggestions:

• None. You either have to class each sheep every year just before joining, or perpetually run your wools separately to your frames.
• Tags. Pick a colour for each classing group. We used to have blue for wools and red for frames.
• Micron buttons. These are little plastic discs that can be slipped over existing tags. We used the Tally Tags and their micron discs.
• Notches in the ear. Obviously this means once you classed them once, they stay as that group for life

 

2. Individually class your ewes into wools or frames at least once in their life prior to their first joining.

Assess each animal into Wool, Frame or Cull. Make your final decision based on whether the sheep's best trait is her Wool or her Carcass. You may also want to have a "Wool OR Frame" group to help you make numbers up one way or the other.

 

3. Similarly class your rams.

Make sure you know how many ewes of each type you have. For example, if you class your ewes into 60% wools and 40% frames, that means you need to divide your rams into 40% wools and 60% frames. This will also help you work out what traits you need to be chasing next time you buy some rams!

 

4. Join wool rams over frame ewes and frame rams over wool ewes.

Just put them out in the paddock together!

 

Next steps for the extra keen

Eliminate error.

If you really want to drive genetic gain, you need to eliminate some of the error in classing. The problem with visual classing is that twin born lambs and lambs out of maidens will always be visually worse compared to singles.

To remove this factor and improve your genetic gain, the next best step is to identify twins and lambs born out of maidens. This requires you to lamb your twin bearing ewes separately and your maidens separately. You will have four groups – older twin bearing, older single bearing, maiden twin bearing and maiden single bearing ewes. Hopefully you are already pregnancy scanning for multiples at this point. If not, that is your lowest hanging fruit, so go do that first!

At marking time, identify the groups (for example a notch in the right ear if it’s a twin lamb and a notch in the left ear if it’s born from a maiden). Then, prior to classing, draft them into the four groups. Class each mob separately, aiming to cull the same proportion from each group.

 

Track parentage to avoid inbreeding.

As commercial producers, we used to join rams with similar parentage together as syndicates. We might have a son, a grandson and maybe a great grandson of lines that we would join in a syndicate. Then at marking, these different progeny groups would be tagged with a different coloured tag. At joining, we drafted into tag colours to ensure daughters weren’t joined to their fathers/grandfathers.

 

Expand outside wools and frames.

Classing into Wools and Frames is a great starting point, but it is also very simplistic. The only limit on your corrective mating strategy is your time and creativity. Maybe you want to progress to a twice-yearly shearing. Then you might class into Long staple wools, Short staple wools and Frames. Perhaps you class into Growthy frames, High Condition score frames, Growthy wools, and High CS wools.

The categories that you choose will depend on what goals you want to achieve. Your first step needs to be to clarify your end goal, then break down the traits you need to be classing for in order to achieve that goal. Give us a call if you want any help! Alternatively, if you want to pay people whose job it is to help you hit your genetic goals, you could always give neXtgen Agri a try.

 

Most importantly, have fun with it and enjoy the game that is merino breeding!