Katahdin FEC EBV's

[St. Lucy's]

I read in the Hairald Katahdin Quarterly that the breed in now using FEC EBV's to identify stud rams with superior parasite resistance. The article mentions samples being sent to "participating labs". In the Lambplan guidelines, fecal samples are to be collected around the time of early weaning weights, which I understand to be 120 day weighing.

Can someone direct me to a source that succinctly explains all this? Which are the participating labs, and in what manner must the samples be sent? Are there criteria such as time elapsed since worming before an acceptable fecal sample can be tested? As I develop my small flock, parasite resistance is something I want to highly prioritize so doing this right the first time (for me) is important.

Brad

[K Bar K Farm]

Brad,

You pose some good questions. I can't answer them, but will add another.........

What if the 120 day weight is in the dead of winter?

[McMurry]

Good questions Brad and and good point Kathy.
IMO (on all points below):
It all sounds highly theoretical doesn't it
The life cycle of this worm is so dynamic and the egg laying phase is so short that it really seems like it would be hard to pull this off with any kind of consistent accuracy. Perhaps if all the variables like Kathy and Brad mention could be controlled and a ton of samples were taken...?
Seems to me the obvious solution is the DNA marker and or performance test under exactly identical parasite pressure which would have to be done at a centralized location with professional oversight / management. I have been looking for data from such a test for a while but have had no luck so far, anyone with any leads?
Even with the relative accuracy of the DNA test, the potential gain in resistance per generation is quite low, looks like it would take quite a few years to establish a significant degree of resistance. We do desperately need that test available to us.
Any of the above systems would be quite expensive to pull off and would take a lot of premium $ charged on a lot of rams to recoup.
http://www.catapultsystems.co.nz/sites/ ... ure_NZ.pdf

[lambchop]

I can answer the date question, samples can be submitted at weaning (40-120) early post weaning, post weaning and url. all with the appropriate age ranges. Don't know the answer to the worming question, but seems to me that worming, then taking samples, would be the wrong way to go.

[St. Lucy's]

On the heritability issue, recent work points towards a 50% heritability from the ram on EBV's, good or bad. So according to this one should be able to make fairly rapid progress.

Brad

[Wclones]

Dr. Notter has a nice section on the FEC EBV in his EBV Description that can be found on the NSIP website.

http://nsip.org/?page_id=1542

I pretty sure they use the McMasters system for the egg count.

[dog]

from Sydney Uni
http://sydney.edu.au/vetscience/sheepwo ... opic9.html
from the CSIRO - has a section on sampling
http://www.csiro.au/files/files/p66p.pdf
these apply to Australian conditions and breeds and may not apply for the USA

[dog]

On the heritability issue, recent work points towards a 50% heritability from the ram on EBV's, good or bad. So according to this one should be able to make fairly rapid progress.

Brad

The australian situation is at least 8 to 10 years of improvement is required - this also evens out with non EBV based selection of worm resistance in some of the South Australian studs. Building a worm resistance flock is a long process - using Lambplan you should see small improvements each year but the payoff will take at least 8 years. The heritability of faecal egg count in Merino sheep is between 0.2 – 0.3 under a typical worm challenge which is much lower then the other production traits.

[McMurry]

Brad,
in support of your statement on high degree of heritability for worm resistance, actually I am quite puzzled by the what I have seen in my flock over the years to that end. I do not know what is going on here but it does seem that it is more easily passed on than the research (at least that I have seen) would suggest. My only guess is that some individual sheep have some behavioral traits (with strong degree of dominance?) that keep them cleaner - perhaps they selectively graze higher in the grass sword Whatever it is, it has held very true for those superior individuals year after year (here).
A solid breeding program using common EBVs for basic performance traits (provided that all the sheep in the group get identical worm prevention treatment), will obviously favor the most resistant individuals and bring them to the top - just in an indirect way.
Cheers, Andy

[Mac Stewart]

I would think that even if the heretibility is low, that for practical purposes one may see quicker improvements in performance on a flock basis. If there is selection pressure for low FEC based on EBVs then you would reducing the number of eggs passed on a total flock basis thus reducing infection time and rate on the sheep in the same flock that are not as far along in genetic improvement.

Mac

[Jim Morgan]

Brad,

I think I answered most of your questions on the phone a while ago, but I think there are some salient points that can be made.

Most of the research around the world, UK, NZ & AU find 20-25% heritability of FEC at 20 weeks of age.

Dr Charles Parker has advocated for years that hair sheep with West African ancestry (e.g. Katahdin, Barbados & St Croix) and Gulf Coast & Florida Natives are different. They can express detectable resistance at 8 weeks that is heritable. Recent research on Katahdins does hold that up and that heritability is 40-50%.

Is the heritability in Katahdins higher than other breeds due to it being a wool hair composite with some sheep very susceptible (Suffolk & Hamp resistant genes) and some sheep very resistant (Virgin Island hair sheep resistance genes)? That could make the heritability appear high. We don't know. Probably not worth the effort, but a study of the heritability of St Croix or Florida Natives would tell us a lot. Dr Jim Miller of LSU found 20-25% in Gulf Coast Native.

This is worth bringing up because it is a great example of BLUP.
The initial Katahdin research by Dr Notter found this. It also shows the importance of Kathy Soder's example of 120 day wt in the middle of winter.
The following two columns are a) average FEC of lamb contemporary group & b) heritability of FEC
< 250 epg 8%
250-500 epg 20%
500-1000 40%
1000+ 52%

In other words, if exposure is low (e.g. < 250 epg contemporary group), FEC is not very heritable. Many of the lambs are not being exposed and have low FECs due to lack of exposure. If exposure is high (FEC > 500 epg for contemporary group), basically no lambs are escaping ingestion of worm larvae and it is quite heritable.

So, if most of your lambs have very low FECs, we can't tell much. LambPlan uses a filter of 500 epg for the FEC contemporary group. LambPlan is set to not results of FECs if the contemporary group has a FEC average of less than 300.

There have been several research projects with Katahdins, NE SARE grant in Maine to Drs Tom Settlemire & Dick Brzozowski, three Farmer/Rancher SARE grants in Ohio to Kathy Bielek, a On-Farm Research Grant in the SE USA & an Organic Systems grant both to Dr Joan Burke and with Drs Dave Notter & Charles Parker collaborating on many of these.

There are several take home messages from the research.
First, selection for parasite resistance using FECs can occur within flock
Second, rate of selection for parasite resistance should occur faster than selection for any other trait that I know of (but one needs a challenge).

No other production trait that I know of can have 3 orders of magnitude difference with in the contemporary group.
60 day wt - 20-30 lbs top to bottom in most cases (factor of 1/2 & 10% heritable)
number born - 1 to 4 or 5 lambs/litter (factor of 5 and 10% heritable)
FEC (range may be 0-2000 or maybe even 15,000 & 20-40% heritable).

Therefore if exposure of the contemporary group is high and there is a range from top to bottom, selection on FEC can have rapid results.

Enough for now. If anyone wants a protocol for selection for parasite resistance, we can do another topic for doing it with EBVs or without. The big advantages of EBVs is that with across flock, we can compare FECs between flocks and thus can related a FEC of 500 in one flock to 1000 in another. Also, increased accuracy.

Regards
Jim Morgan

[Ebenezer]

We have St Croix so we start with great advantage. But the greater rate of improvement within a flock is not merely selecting for the most resistance but the culling of the least or the non-resistant.

[Jim Morgan]

Good point. Any selection system is much improved by having top & bottom area with at least some accuracy of measurement and then lots of room in between so that .

This is an advantages of most if not all EBVs. Identifies the top, middle and the bottom.
Can make two points.
1) Range of EBV
WFEC (Weaning Fecal Egg Count Range) -93% to + 418%
PFEC (Postweaning Fecal Egg Count Range) -100% to 848%
(weaning is 60 days of age; post weaning is 120 days of age +/- 30 days)
Can make a lot progress with those ranges. The key in the next few years will be to have enough -75% ewes to breed to the better high ranking rams

2) Range of Raw FECs versus FAMACHA versus Bottle Jaw versus Packed Cell Volume
If your contemporary group has a range of FECs can make much better progress using FEC than any other measure.

Technique - Range
Bottlejaw - yes/no or 0 & 1
FAMACHA - 1 to 5
PCV - 8% to 33%
FEC - 0 to 15,000 (maybe 35,000)

FEC is very powerful selection tool. Don't recommend pushing the contemporary group to the extreme of 0-35,000 epg; but a 0-2000 epg contemporary group range is an excellent range to make good progress. It separates the top from the bottom adequately.

Use of an EBV system allows more accurate selection when range of FECs in the contemporary group are smaller e.g. 0-1000 epg.

Jim

[St. Lucy's]

In discussing this with Kathy Bielek, I found that the age they have been using in their SARE grant studies for testing heritability is "first challenge" for the lambs - which is more weather/seasonal related than age related. This is what Kathy is using to determine her best FEC ram lambs (I have one; last years sire for my small flock). How does this intersect with Lambplan specified dates for FEC testing?

Brad

[Jim Morgan]

Brad,

They are the same. Kathy's data is going into NSIP.
The way to think about it is that it is similar to wts. Not all sheep are weighed exactly at 60 days of age, but all those in runs 62, 64 & 69 all receive a WWT EBV (which is adjusted to 60 day EBV). Katahdin FEC EBV for WFEC and PFEC are the same. Analysis adjusted to a FEC at 60 day for WFEC and 120 days for PFEC. The reason for bringing up the 60 day is to indicated that if challenge is present, the heritable resistance to Barberpole can be documented as early as 60 days.

Earlier in the thread, the importance of challenge was mentioned. If the first challenge is at 140 days, that would be analyzed at the PW age. There is about a 60% correlation between an FEC EBV for 60 days and FEC EBV at 120 days. So, a measure for one will result in EBVs for both.

Has to be a worm challenge to differentiate resistance between animals. In most cases buying sheep from a flock that never deworms to get parasite resistant sheep doesn't work. First, if the flock does need deworming and there is no measures to differentiate, one can be buying the best or worst sheep. One actually needs to buy from a flock that has to deworm and has a system that can detect differences in resistance. If you buy sheep from a flock that never deworms, one does not know whether they are getting the best sheep or the worst sheep of the flock or if the lack of deworming is due to management or environment.

Regards
Jim