We have a load of buzzards here too and, the day before the littlun was slashed the neighbour, who keeps quail, had a Sparrowhawk in his garden but I doubt that would have done that kinda damage. The pair of sea eagles nesting in the trees above the loch are the most likely candidates. They've been years nesting there now. Some wildlife 'expert' who works for a marine organisation in Greenock tried to tell me that it wouldn't have been a bird of prey but it can't have been anything else. Our garden is fenced all round with six foot high fencing and locked gates in a backwater of an already quiet village and there is nothing that could have done the damage in the garden and certainly not in an up/down slash on her side. As the vet said, if she had caught on anything it would have torn along her body.
I could imagine her bragging about it too. Her fur has grown back now and you can only see a hint in the fur of where the slash was and all you can feel of it is a little lump at one point on the scar where I guess the tissue got a little knotted up.