* 1.Crops — eliminate the exposure to the spores. A great option.
Pros — could be a higher quality feed on offer compared to existing pasture. This means it not only eliminates spore ingestion but it is likely to have flushing effect, although lucerne and red clover are not suitable.
Cons — hard to budget on how long they need to be on this feed because of the vagaries of the length of the facial eczema challenge period. Are crops economically viable for this purpose?
With 1000 ewes currently lambing 120 per cent, if you produce an extra 10 per cent lambs, at $3/kg LW for a 25kg lamb that is an extra $7500 in income.
Cost of the crop (rape) to carry 1000 ewes (eating 1.5kgDM/day/ewe) for six weeks is…
13Ha (5 tonne crop) at $700/Ha to plant it = $9100 (so doesn't work financially).
The break-even point scenario for this rough calculation is an extra 120 lambs or 12 per cent. Another way to look at it is not losing 120 lambs that might have not made it through to sale from a poor scanning result and/or ewes packing up at lambing.
What this crude calculation doesn't take into account is many factors including:
Is the eczema period only six weeks?
The extra grass grown when they are off pasture for six weeks in autumn.
This might actually set you up nicely to hit the magical 2000kgDM/Ha average cover by May 1, heading into winter.
The crop needs to be managed for a second grazing regrowth if that was the plan, or you may just want one bulky crop.
We need to also consider cost — financial and environmental — and outcomes from putting the paddock back into pasture. To get 12 per cent extra lambing percentage is roughly around a 20 per cent scanning lift.
Ewe lifetime performance is improved, dry rate lowered and ewe death rate lowered
If you are scanning less than 155 per cent, and poor feed quality and/or eczema are risks for you then crops could be a viable option.
You could trial it on a smaller scale with the B mob or light ewes first until you get the recipe/management perfected and then expand it to the whole mob if the gains are obvious.
We have experience in use of crops at this time of year and can help with planning.
* 2. Zinc capsules — prevent the toxin damaging the liver.
Great short term option, although no one likes administering these big capsules and the ewes may remember it.
Pros — works well when administered at the right time (immediately prior to the rise in counts).
Cons — if the eczema season isn't aligned with the mating season ie is early or late then you may need a second capsule to get through mating with no upset to ewe fertility.
Conclusion:
Easiest short term management tool when administered at the right time. Long eczema seasons can be problematic meaning a second capsule may be required.
* 3. Genetics — let the animals cope successfully with the challenge.
Best long term option but you may need to use option 1 or 2 along the journey before adequate tolerance is reached. It is a highly heritable trait (h=0.45).
There are a few strategies to assist in the development of a facial eczema ewe flock to minimise the wastage this disease causes.
a. Rams — these supply 80 per cent of the genetic merit to the flock. Buying rams from flocks testing at the highest levels (0.6mg/kg) is the best way to go.
However it is not perfect. FE Gold is the brand developed to highlight these breeders dosing at the high level and it's a great achievement taking 20-30 years of commitment to get there.
However only 10 per cent of the rams need to be dosed with the sporidesmin toxin, with no or minimal resulting liver damage, to qualify each year.
The other 90 per cent are not dosed. Hopefully the breeder is spreading the tolerant genetics through the flock effectively to make sure the sale rams will all offer the same reputation of a dosed ram. This can be backed up by looking at the SIL figure (now nPROVE) for DPX or dual purpose eczema tolerance. This is the figure you need to give close attention. The bigger the number, the more tolerant they are.
b. Ewe hoggets — during an eczema challenge period, there will be a range in severity of damage occurring to the liver of the ewe hoggets. You can identify which ewe hoggets are affected compared to others with a simple blood test. Note- the skin lesions you see in visibly affected sheep actually only occur in a small portion of the mob unless the challenge is severe.
The test costs $12/head + $1/head for our techs to take the sample + travel.
Being in an inconsistent area for FE means the ewe hoggets may not be exposed every year and so this test may not be able to be used every year.
Conclusion:
Using genetically tolerant rams and choosing the most tolerant ewe replacements will result in rapid progress for this trait.
All terminal sires should be treated with a zinc capsule if there is any risk around mating.
