A lot more happens behind the scenes in a modern, performance focused ram breeding operation. While most lamb producers focus on 2 or 3 traits when buying rams (traits like growth rate, fat, muscle and birthweight), as breeders we now have 9 different traits included in our selection index of ebvs. Clearly the primary profit drivers like pwt (growth rate) have the biggest impact on the index, but a range of these newer traits are included to prevent a breeding program going off track – like breeding rams with poor eating quality, or to advance selection for easycare production through traits like lambing ease.
I like to think of these as the free bonus you get when you buy a Felix ram.
Lambing Ease Direct (LE_DIR)
Lambing Ease is a trait we have been recording since 1994, and have included it in our selection index for the last 3 years. Dams are scored for their ease of lambing – observed, easy assist, difficult assist or abnormal presentation, and this is used alongside birthweight information to generate lambing ease direct (the rams affect on lambing ease) asbvs.
This trait is important to prevent increasing muscle and thickness in lambs impacting on their ability to be born with ease. For a lamb producer lambing ease direct (LE_DIR) is the trait that affects their production. Lambing ease information is also used for producing ebvs for lambing ease daughters (LE_DAU). This is a maternal trait and isn’t important when buying rams for prime lamb (terminal) production system.
To produce asbvs there needs to be variation in a trait, and with lambing ease, unless you are having to assist lambs at birth, there is nothing to record. These few records are combined with birthweight records (every lamb), and in most cases there is a strong correlation between BWT and LE_DIR asbvs.
We have only supplied LE_DIR asbvs on request to producers. The chart below shows how we have been able to improve this trait in recent years. The WS line in the chart highlights how quickly this trait can change.
With LE_DIR, a positive value means greater lambing ease, and a negative value is more lambing difficulties. Only a limited number of Sheep Genetics users record lambing ease.
Post Weaning Worm Egg Count (PWEC)
It surprised when I checked the records that we have been recording this trait since 2008.
To get data for this you need to get lambs wormy – no more than 10% with zero counts, and average over 200. Sounds simple, but not always easy in a dry spring. A good raiin mid spring like this year seem to be ideal to develop the worm burden.
For the main June/July drop we only collect samples from the ram lambs as the ewe lambs rarely get wormy enough to have good data. For the spring drop we do both ram and ewe lambs to get better coverage of the sires used as they tend to have less lambs in this group. Most years this means 500+ individual fecal samples.
A more negative PWEC means lower worm egg burdens, and we are making reasonable progress in reducing PWEC. Despite the significance of worms to production, and the ongoing development in drench resistance, few producers seem to take much notice of the pwecasbvs when they make their selections. One comment I have heard a few times is “as long as its negative I’m happy”. Fortunately almost all the leading ram breeders who use abvs seriously are collecting samples and getting pwecasbvs on their rams. Adding to this some information from the dna tests on PWEC, although it is one of the last accurate asbvs from genomic information.
PWEC has been in our index since we started recording it, and I think we’re making good progress on reducing pwec, and have sufficient depth of information on this trait to easily ramp up selection pressure if requested by clients.
PWEC isn’t the easiest trait too collect. You have to be able to give the animals a worm challenge after you have given them an equal start after an effective cleanup drench at weaning. Electronic id’s have proved invaluable when collecting the samples, and matching an electronic id list to samples. It’s a messy job, and you have to be committed to getting the data. Only about 15-20% of Lambplan users collect PWEC data.
Eating Quality and Lean Meat Yield
DNA tests for a range of traits, but most importantly for eating quality and yield, have been commercially available from the Sheep CRC for 4 years. Prior to this there was some information on rams that had been used in the Information Nucleus, and other trials associated with the CRC.
Based on consumer taste testing it is recommended to have a minimum for Intramuscular Fat (IMF) of 0, and the maximum for Shear Force (SHRF) was 0. Simply, IMF had to be positive and Shear Force had to be negative.
We had quite a few animals involved in the Information Nucleus, and it was very apparent to me that there were very few Poll Dorsets that fitted that requirement. By comparison our (and most) White Suffolks were very good for IMF. There was a reasonable expectation that if we didn’t put some selection pressure on eating quality if would only get worse.
For the last 4 years we have DNA tested between 50 and 80 young rams from each drop, including every ram we have used. Each DNA test cost $50. Blood samples are taken a few weeks after weaning.
While the chart indicates we are making progress, it is a slightly biased sample. The entire drop isn’t tested. We do test all sire lines from the drop, and what the chart really shows is that we have the potential to select better eating quality rams each year from those tested.
As it seems is always the case, good eating quality is negatively correlated with lean meat yield (LMY). Our Poll Dorsets were relatively good for LMY and poor for IMF, while our White Suffolks were good for IMF, and poor for LMY. Again consistent with other breeders.
Again this is the same biased sample, but it indicates that we are making progress with the White Suffolks, and almost maintaining LMY in the Poll Dorsets while improving IMF and other traits.
It doesn’t matter how hard you look at a ram, you cannot predict the performance of his progeny for these traits through visual inspection. There have been many theories promoted by judges, such as coarse wool would mean coarse-grained meat, but none have been backed by analysis in the coolroom, or through consumer testing.
If you don’t measure it you can’t select for it, but the more traits you select for, the less progress you will make in any one of them individually. Poor breeding practice is to focus on only one or two traits. Almost certainly if you do, if will be to the detriment of others. The classic is birthweight and growth rate. Selecting for high growth rate without emphasis on keeping birthweight moderate, will just lead to higher birthweights and more dystokia.
The challenge for us is to get the balance right – produce high performance in the traits most producers want, but be aware of the potential needs of the industry and consumers going forward. The industry has the tools to maintain and improve eating quality. It would be negligent for a ram breeder not to use them.
As you would expect, our index is constantly under review.
