Signs of depression surrounded by horses?

My mare is an "only horse", she seems to be happy, is a awfully laid back gal, are there any signs of depression to look for?

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dunno google it or ask the vet.

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a sunny horse moves about in its pasture and "look" at things..
a depressed horse just stands for hours beside its head low.. no running or playing.. no interest when you add new things..

breed sure your horse as toy - like a 4litre milk container with 3 small rocks - an inner tube or a horse "ball"..

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Answers:    You are kidding, right?

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