I posted this on the subject a few days ago:
Waste of time. We can only do so much to protect trees. If a resilient tree is found and worth protecting, put a fence around it! Even if you guard it 24/7 with a rifle, something out of season can still eat it or anything can eat it at night! Culling is only a means to support other means of protection and general area damage reduction. The only real way to stop deer eating something is to prevent them getting anywhere near it in the first place! There is no way to prevent the ash tree loss now, it's too late. Culling excessive deer will merely be a 'knee-jerk' reaction which will serve no purpose other than to reduce the population which is too high already as highlighted. The general landscape and woodland will undoubtedly benefit, but the ash is doomed anyway!
As an aside, one of the things I do is woodland deer impact assessment. One of the most important parts of this is to try to establish which species are having the most impact. I have found that the worst damage on Ash trees is leading stems being broken off at about chest height. The culprits are Fallow! Muntjac and Roe don't seem to bother with ash that much other than the odd leaf. The disease has now been found in all of the ancient woods that I manage for the wildlife trust!
Dave G is exactly right in that ANY amount of deer will destroy the regeneration at its most vulnerable time which is in the first few years of growth. Culling can only ever support other forms of management, unless you cull them all which is clearly never an option! Areas, or even individual trees will have to be enclosed if you want them protected from deer. It's not just deer either! Brown hares are as much to blame around here as there are thousands of them, and they do actually live in the woods! Do we shoot all of them too even though they are a 'BAP' species? Then there are the rabbits!
The local trust operate on a 25 year coppice cycle which leaves exposed coppiced stools to regenerate. Trying to protect them has proved to be impossible through culling alone for the reasons already stated. We use a portable chestnut pale fence which remains around a freshly coppiced area until the main shoots are away out of deers reach. The fence rungs are also narrow enough to exclude the hares! We have also started to use the 'Heras' style fencing which doesn't look too good in a woodland, but is only temporary and works extremely well as it is fine mesh and also quite high.
It is also reasonable to assume that other tree species will regenerate and fill the gaps left by the ash canopy? These will also suffer as much as the Ash with the current burden of excessive deer. We do need to cull more deer in this area generally, but this is not a new issue just because of the Ash disease!