What is wrong with my friends horse!?

She is 7 1/2 yo OTTB mare and i'm taking care of her and the other animals for my friend while she is away. I just got back from feeding them she lives about 10 minutes away and noticed that the mare didn't even touch her food and was looking a little weary and grunted a little like she was hurting. I've heard of things like colic but am not exactly sure what it is. My friend left me her vets phone # should i have him come out and check her?Any help is greatly appreciated!Thanks in advance