Very nice consultant from SAC came out today. What I feared was ergot is ergot. We walked the field and it's widespread--- not great swathes of it, but everywhere we stopped to look we found a few scattered affected seed heads. So my first thought of walking round the field zapping it with a blow torch weed killer thing is out of the question.
He was pretty gloomy. There's no chemical control, and the only way to be 100% safe is to not use the grazing for livestock. I don't have that option, so he suggested topping it high, to leave as much leafy green stuff as possible, leaving it to dry, and the ergots will hopefully drop down to ground level and not be eaten. It's not great, but it's better than just leaving it, because while it's on standing stalks they will eat it accidentally while eating the greenery.
I suppose this will also have the benefit of scattering the ergots around, so even if some are eaten accidentally it won't be enough to do harm.
He said baling and burning would be pointless because the ergots would probably all fall out in the process of baling.
The ergots will stay dormant in the soil so I will have to top repeatedly next summer so the grass just doesn't get a chance to flower. Without flowering heads there will be no ergot.
I'm not happy. I don't like solutions that aren't good solutions, but I don't seem to have any options.