Reducing errors in classing

"Data will talk to you if you're willing to listen to it." ~ Jim Bergeson

It's just starting to turn cold here after a couple of fantastic growing months! I hope you are also enjoying some green feed and happy sheep 🙂.

Important news for Longreach clients

It's only 6 weeks until the Longreach sale! The date was set for 19 July, but the showground may have double booked us. We will send you another email as soon as the date is confirmed.

Reducing errors in classing

When classing ewes, the main priority should be to select the ones that will produce the best progeny to meet your goals.

If you're like us when you're classing sheep, you'll be concentrating hard on what you see in front of you. Unfortunately, what we see is not the genetics of that animal. It is a combination of genetics, the environment, your management, and its in-utero experience.

In order to select the ewes with the best genetic potential, we need to eliminate the non-genetic factors as much as possible.

Last month we talked about how two ewes with the same genetic potential (meaning that their lambs will be equally good) could look very different if one gave birth to twins and the other only gave birth to a single lamb. They could also look very different if they were run in different paddocks.

Birth groups

Another major influence over how a sheep appears visually is whether it was born a twin or single, or whether it was born from a maiden ewe.

In each case, these animals essentially spent the first 5 months of their life (in the womb) in different paddocks! The maiden ewe is still maturing, so she doesn't put as much energy towards the lamb and also doesn't milk as well (she's still learning how to be a mum!) Twins have to share nutrition with their sibling.

The graph below, compiled by Mark Ferguson from neXtgen Agri, shows the many differences between twins and singles, based on nothing but the fact that they were a twin or single.

Phenotypic differences between twins and singles.

Many of these things are only small, but the accumulation of lots of slightly worse traits results in more twins being culled even though they are genetically the same as singles.

Singles from a maiden ewe perform worse than twins from an older ewe, and twins from a maiden perform even worse again.

Therefore, it is important to know which lambs are singles and twins, and which lambs are born from maidens.

Preg scanning

Practically, what this means is that you must pregnancy scan your ewes for multiples. (Hopefully you are already doing that after the last article!)

Then, prior to lambing time, draft into these four groups:

1. Older single bearing ewes.
2. Older twin bearing ewes.
3. Maiden single bearing ewes.
4. Maiden twin bearing ewes.

Unless you have EIDs and an autodrafter, the best way to do this will be to separate the twins and singles at pregnancy scanning and keep them separate until after lambing. Prior to lambing, draft the maidens off into their own twin mob and single mob.

An added benefit is that you can also provide your twin-bearing ewes with better quality paddocks!

You may want to split them up even further to have the benefit of smaller lambing mobs, but keep those 4 groups separate.

Drafting ewes.

Then, at marking time, bring these mobs in separately and identify the lambs in their four groups. You could do this with different coloured tags, or ear notches or similar.

However, an easier way is to make use of the EID tags we are being forced to start using next year.

Using EID

You want to create a field called “Birth group” with 4 options:

1. MA single (Single lamb born from a Mixed Age ewe)
2. MA twin
3. Maid single (Single lamb born from a Maiden ewe)
4. Maid twin.

You can use any other terms that make sense to you. “Old single”, for example.

Lamb marking time!

Next, you need to record each animal's status at marking time. There are a couple of ways you can do this with almost no extra work.

1. Set up your EID reader to auto-record the correct status; e.g. “Maid single” for your mob of singles born from maidens. Set your EID reader to auto-scan. Next, as you pick up each tag, wave it past the reader so that it records that tag as (in this example) “Maid Single”.
2. When tagging, keep the tags in numerical order. Write down the tag number that you started the mob with and the tag number that you ended with. Then, download the bucket list (this is the list of tags from the supplier which has the EID, Visual ID and NLIS ID of every tag you buy.) You will use this file to select all the tag numbers that match the mob you just marked (for example, every tag from 24-5134 to 24-5234) and change them all to the correct “Birth group”. How exactly you do this will depend on which EID reader and software you use.

At classing time

Ideally, you would class the four groups separately:

1. Singles from old ewes.
2. Twins from old ewes
3. Singles from maidens.
4. Twins from maidens.

In most situations, it will be easier for drafting to get down to 3 mobs. In that case, groups 2 and 3 are the most similar.

On average, each group will have the same spread from best to worst, so the idea is to cull the same percentage of sheep from each group. At the end of the day, if you culled only 20% of your singles and 40% of your twins, you culled some decent twins and kept some sub-par singles.

Your brain is pretty incredible and adjusts to the average of what you see in front of you, so this is usually not too difficult to achieve.

If you think that drafting into separate mobs is too time-consuming, you can instead scan their EID tag to see their birth group as you class. That way, when a twin from a maiden follows a single from an older ewe, you won't immediately class it out because it looks worse. Instead, you mentally add a couple kg to what you see, and improve the wool traits by a fraction of a score to account for the birth effects.

Be prepared to make the most of the EID tags we are being forced to use.
The Rissmerino team