Great info. Just went to calving school and if you have to pull the vet recommended turning the calf sideways (in a normal presentation) once you get past the rib cage so there's less damage to the cow from the calf's hips (plus it's easier to get the rest of the calf out). He also recommended using nylon OB calf straps instead of chains because they're less painful on the calf's legs & reduces the chance of breaking or injuring a leg - I just ordered some from Valley Vet.