I find the safest feed troughs are the bases of blue plastic 45 gall drums. The barrels are @£5 each and you get 2 robust troughs from each - one from each end.
I used to use long yellow plastic ones - made from high pressure gas piping. Like Womble I would race to one end and run along to fill the trough but there would always be at least one sheep that had to overtake me and attempt to trip me up. This would slow me down sufficiently that I was surrounded by sheep before I got to the end and they always had to have their head in the trough so I couldn't even pour the food in.
Then - enter the blue plastic troughs.
they will comfortably fit 6 sheep round at a time, although up to 100 will attempt to fit in the first trough before the rest are filled. Because they are circular, you can throw a scoop into the first. This diverts the entire flock and while they are fighting over a single trough, you can safely go and fill up the rest. They don't try and get ahead of you like they do with a long trough because they don't know which one you're going to fill next.
Then gradually the sheep disperse to the remaining troughs and have been safely fed without tripping you up, nor the necessity for foul language and an increasing hatred of sheep. They really do spread out to a max of 6 sheep/trough so you know instantly whether you have sufficient trough space. The troughs are also easily tipped up to get water out or clods of earth etc.
