Sunday, March 3, 2024

Coping with facial eczema

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This year has been a bad one for facial eczema (FE) over a much wider area than normal. So how can genetics help? You can buy FE-tolerant rams to breed this into your ewe flock, but a similar option is not available for beef or dairy cattle. Remember your local vet can advise on animal health strategies to reduce the effects of FE outbreaks on your farm. Why is there a selection system for sheep but not for cattle? Simply because a number of dedicated ram breeders have been selecting for 30 years for greater FE tolerance using the RamGuard service offered by AgResearch. Over many years these breeders have slowly increased the challenges animals get and selected the animals that show the least effect of FE. This hasn’t happened in cattle. SIL has a list of flocks certified as selecting for FE tolerance using RamGuard – click here for the list. The New Zealand industry owes a lot to the breeders who have bred FE tolerance into their flocks. However, it’s not all beer and skittles to get this tolerance into a commercial ewe flock.
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Not all FE-tolerant animals have the same level of tolerance. The system used for selection tests animals at a level that will not severely affect them for sound and critically important animal welfare reasons.

So flocks that have not been selecting for long using RamGuard are likely to be testing at a lower level. And if they are not using RamGuard, instead buying FE-tolerant rams from breeders to use as sires, progeny of those sires are expected to have only half the FE tolerance of their sire.

So how can you tell the difference? This is where it’s simple – ask a ram breeder to see their RamGuard certificate to prove they’re testing.

On the certificate will be detailed the level they’re testing at. Testing levels range from 0.2 (low) to 0.6 (high).

SIL has a list of certified FE-tolerant flocks that details the level flocks are testing at from one star (0.2) to five stars (0.6).

A ram breeder needn’t have been selecting for 30 years to be testing at the highest level. RamGuard carefully monitors responses in tested animals and only lifts the level of challenge when responses have been weak the previous year.

Some ram breeders have “sprinted” to where they are now by buying seriously high-tolerance rams from pacesetter breeding flocks to fast-track their breeding programme.

This is helped by FE tolerance being highly heritable. A recent estimate from SIL data gave a figure of 42%.

Few commercially important traits are this heritable so it’s possible to make very good selection progress for this trait compared to many others.

Breeders testing at the highest level have banded together to create the FE Gold brand for flocks testing at a high level. If a ram breeding flock uses this brand you can expect to buy rams with a genetic background of the highest level of FE tolerance.

If you are targeting FE tolerance in particular, tell your ram breeder. They can steer you towards the best genetics for this in rams on offer.You may have to pay quite a premium for this, given the season we have just had but you are the best judge of its worth.

Unfortunately, changing your ewe flock from an FE-susceptible flock to an FE-tolerant flock is not going to happen overnight.

You need to commit to an ongoing policy of buying FE-tolerant rams for a number of years because the first crop of lambs will have only half of what their sires carry and ewes are in the flock for a number of years.

It will be some years before all your ewes are three-quarters FE-tolerant bred or greater.

Buying FE-tolerant rams can be a real investment in the future of your ewe flock but it is something you must embark on now if you want an FE-tolerant ewe flock in five to 10 years time.

The take-home message: check out the independently produced RamGuard certificate to show how FE tolerant a ram-breeding flock is.

You can also see how long they’ve been selecting for FE tolerance using the RamGuard-certified flock list on the SIL website.

If you have any questions about this topic send an email to silhelp@sil.co.nz or leave a message on 0800-silhelp (0800 745 435).

• Mark Young is senior geneticist with B+LNZ Genetics and SIL.

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