Sorry to hear of your losses but have to agree with lazybee.
Secure fencing is the way to go or if freeranging (in my experience, no matter what part of the country), Renard usually visits lunchtimes.
You might be able to see which direction he took off in, as often there is a trail of the odd feather here and there on the grass, then a pile of feathers a couple of fields away, once foxy feels safe enough to pause.