I mean I guess if this is all you can get then it's fine. There's two things I see a little iffy here is that 1) they are a resident in surgery so the likelihood that they really are able to assess you may not have been that great. and 2) as a DO letter, it would have been better to see it from the side of a primary care specialty to "notice the DO difference" as it pertains to the use of OMM or anything of that sort.
I have a letter of rec from an MD but this is the only D.O. one I have because my summer opportunity got canceled. Would this be okay when applying to D.O. schools? I'm also Canadian so I think they will be stricter on me